Add non-animated SSSE3 blitter

[openttd/fttd.git] / src / roadveh_cmd.cpp

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file roadveh_cmd.cpp Handling of road vehicles. */

#include "stdafx.h"
#include "roadveh.h"
#include "command_func.h"
#include "news_func.h"
#include "station_base.h"
#include "company_func.h"
#include "articulated_vehicles.h"
#include "newgrf_sound.h"
#include "pathfinder/yapf/yapf.h"
#include "strings_func.h"
#include "map/road.h"
#include "map/depot.h"
#include "map/tunnelbridge.h"
#include "date_func.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "ai/ai.hpp"
#include "game/game.hpp"
#include "effectvehicle_func.h"
#include "roadstop_base.h"
#include "spritecache.h"
#include "core/random_func.hpp"
#include "company_base.h"
#include "core/backup_type.hpp"
#include "newgrf.h"
#include "zoom_func.h"
#include "bridge.h"
#include "station_func.h"

#include "table/strings.h"

static const uint16 _roadveh_images[] = {
        0xCD4, 0xCDC, 0xCE4, 0xCEC, 0xCF4, 0xCFC, 0xD0C, 0xD14,
        0xD24, 0xD1C, 0xD2C, 0xD04, 0xD1C, 0xD24, 0xD6C, 0xD74,
        0xD7C, 0xC14, 0xC1C, 0xC24, 0xC2C, 0xC34, 0xC3C, 0xC4C,
        0xC54, 0xC64, 0xC5C, 0xC6C, 0xC44, 0xC5C, 0xC64, 0xCAC,
        0xCB4, 0xCBC, 0xD94, 0xD9C, 0xDA4, 0xDAC, 0xDB4, 0xDBC,
        0xDCC, 0xDD4, 0xDE4, 0xDDC, 0xDEC, 0xDC4, 0xDDC, 0xDE4,
        0xE2C, 0xE34, 0xE3C, 0xC14, 0xC1C, 0xC2C, 0xC3C, 0xC4C,
        0xC5C, 0xC64, 0xC6C, 0xC74, 0xC84, 0xC94, 0xCA4
};

static const uint16 _roadveh_full_adder[] = {
         0,  88,   0,   0,   0,   0,  48,  48,
        48,  48,   0,   0,  64,  64,   0,  16,
        16,   0,  88,   0,   0,   0,   0,  48,
        48,  48,  48,   0,   0,  64,  64,   0,
        16,  16,   0,  88,   0,   0,   0,   0,
        48,  48,  48,  48,   0,   0,  64,  64,
         0,  16,  16,   0,   8,   8,   8,   8,
         0,   0,   0,   8,   8,   8,   8
};
assert_compile(lengthof(_roadveh_images) == lengthof(_roadveh_full_adder));

template <>
bool IsValidImageIndex<VEH_ROAD>(uint8 image_index)
{
        return image_index < lengthof(_roadveh_images);
}

static const Trackdir _road_reverse_table[DIAGDIR_END] = {
        TRACKDIR_RVREV_NE, TRACKDIR_RVREV_SE, TRACKDIR_RVREV_SW, TRACKDIR_RVREV_NW
};


/**
 * Check whether a roadvehicle is a bus
 * @return true if bus
 */
bool RoadVehicle::IsBus() const
{
        assert(this->IsFrontEngine());
        return IsCargoInClass(this->cargo_type, CC_PASSENGERS);
}

/**
 * Get the width of a road vehicle image in the GUI.
 * @param offset Additional offset for positioning the sprite; set to NULL if not needed
 * @return Width in pixels
 */
int RoadVehicle::GetDisplayImageWidth(Point *offset) const
{
        int reference_width = ROADVEHINFO_DEFAULT_VEHICLE_WIDTH;

        if (offset != NULL) {
                offset->x = reference_width / 2;
                offset->y = 0;
        }
        return this->gcache.cached_veh_length * reference_width / VEHICLE_LENGTH;
}

static SpriteID GetRoadVehIcon(EngineID engine, EngineImageType image_type)
{
        const Engine *e = Engine::Get(engine);
        uint8 spritenum = e->u.road.image_index;

        if (is_custom_sprite(spritenum)) {
                SpriteID sprite = GetCustomVehicleIcon(engine, DIR_W, image_type);
                if (sprite != 0) return sprite;

                spritenum = e->original_image_index;
        }

        assert(IsValidImageIndex<VEH_ROAD>(spritenum));
        return DIR_W + _roadveh_images[spritenum];
}

SpriteID RoadVehicle::GetImage(Direction direction, EngineImageType image_type) const
{
        uint8 spritenum = this->spritenum;
        SpriteID sprite;

        if (is_custom_sprite(spritenum)) {
                sprite = GetCustomVehicleSprite(this, (Direction)(direction + 4 * IS_CUSTOM_SECONDHEAD_SPRITE(spritenum)), image_type);
                if (sprite != 0) return sprite;

                spritenum = this->GetEngine()->original_image_index;
        }

        assert(IsValidImageIndex<VEH_ROAD>(spritenum));
        sprite = direction + _roadveh_images[spritenum];

        if (this->cargo.StoredCount() >= this->cargo_cap / 2U) sprite += _roadveh_full_adder[spritenum];

        return sprite;
}

/**
 * Draw a road vehicle engine.
 * @param left Left edge to draw within.
 * @param right Right edge to draw within.
 * @param preferred_x Preferred position of the engine.
 * @param y Vertical position of the engine.
 * @param engine Engine to draw
 * @param pal Palette to use.
 */
void DrawRoadVehEngine(int left, int right, int preferred_x, int y, EngineID engine, PaletteID pal, EngineImageType image_type)
{
        SpriteID sprite = GetRoadVehIcon(engine, image_type);
        const Sprite *real_sprite = GetSprite(sprite, ST_NORMAL);
        preferred_x = Clamp(preferred_x, left - UnScaleByZoom(real_sprite->x_offs, ZOOM_LVL_GUI), right - UnScaleByZoom(real_sprite->width, ZOOM_LVL_GUI) - UnScaleByZoom(real_sprite->x_offs, ZOOM_LVL_GUI));
        DrawSprite(sprite, pal, preferred_x, y);
}

/**
 * Get the size of the sprite of a road vehicle sprite heading west (used for lists).
 * @param engine The engine to get the sprite from.
 * @param[out] width The width of the sprite.
 * @param[out] height The height of the sprite.
 * @param[out] xoffs Number of pixels to shift the sprite to the right.
 * @param[out] yoffs Number of pixels to shift the sprite downwards.
 * @param image_type Context the sprite is used in.
 */
void GetRoadVehSpriteSize(EngineID engine, uint &width, uint &height, int &xoffs, int &yoffs, EngineImageType image_type)
{
        const Sprite *spr = GetSprite(GetRoadVehIcon(engine, image_type), ST_NORMAL);

        width  = UnScaleByZoom(spr->width, ZOOM_LVL_GUI);
        height = UnScaleByZoom(spr->height, ZOOM_LVL_GUI);
        xoffs  = UnScaleByZoom(spr->x_offs, ZOOM_LVL_GUI);
        yoffs  = UnScaleByZoom(spr->y_offs, ZOOM_LVL_GUI);
}

/**
 * Get length of a road vehicle.
 * @param v Road vehicle to query length.
 * @return Length of the given road vehicle.
 */
static uint GetRoadVehLength(const RoadVehicle *v)
{
        const Engine *e = v->GetEngine();
        uint length = VEHICLE_LENGTH;

        uint16 veh_len = CALLBACK_FAILED;
        if (e->GetGRF() != NULL && e->GetGRF()->grf_version >= 8) {
                /* Use callback 36 */
                veh_len = GetVehicleProperty(v, PROP_ROADVEH_SHORTEN_FACTOR, CALLBACK_FAILED);
                if (veh_len != CALLBACK_FAILED && veh_len >= VEHICLE_LENGTH) ErrorUnknownCallbackResult(e->GetGRFID(), CBID_VEHICLE_LENGTH, veh_len);
        } else {
                /* Use callback 11 */
                veh_len = GetVehicleCallback(CBID_VEHICLE_LENGTH, 0, 0, v->engine_type, v);
        }
        if (veh_len == CALLBACK_FAILED) veh_len = e->u.road.shorten_factor;
        if (veh_len != 0) {
                length -= Clamp(veh_len, 0, VEHICLE_LENGTH - 1);
        }

        return length;
}

/**
 * Update the cache of a road vehicle.
 * @param v Road vehicle needing an update of its cache.
 * @param same_length should length of vehicles stay the same?
 * @pre \a v must be first road vehicle.
 */
void RoadVehUpdateCache(RoadVehicle *v, bool same_length)
{
        assert(v->type == VEH_ROAD);
        assert(v->IsFrontEngine());

        v->InvalidateNewGRFCacheOfChain();

        v->gcache.cached_total_length = 0;

        for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
                /* Check the v->first cache. */
                assert(u->First() == v);

                /* Update the 'first engine' */
                u->gcache.first_engine = (v == u) ? INVALID_ENGINE : v->engine_type;

                /* Update the length of the vehicle. */
                uint veh_len = GetRoadVehLength(u);
                /* Verify length hasn't changed. */
                if (same_length && veh_len != u->gcache.cached_veh_length) VehicleLengthChanged(u);

                u->gcache.cached_veh_length = veh_len;
                v->gcache.cached_total_length += u->gcache.cached_veh_length;

                /* Update visual effect */
                u->UpdateVisualEffect();

                /* Update cargo aging period. */
                u->vcache.cached_cargo_age_period = GetVehicleProperty(u, PROP_ROADVEH_CARGO_AGE_PERIOD, EngInfo(u->engine_type)->cargo_age_period);
        }

        uint max_speed = GetVehicleProperty(v, PROP_ROADVEH_SPEED, 0);
        v->vcache.cached_max_speed = (max_speed != 0) ? max_speed * 4 : RoadVehInfo(v->engine_type)->max_speed;
}

/**
 * Build a road vehicle.
 * @param tile     tile of the depot where road vehicle is built.
 * @param flags    type of operation.
 * @param e        the engine to build.
 * @param data     unused.
 * @param ret[out] the vehicle that has been built.
 * @return the cost of this operation or an error.
 */
CommandCost CmdBuildRoadVehicle(TileIndex tile, DoCommandFlag flags, const Engine *e, uint16 data, Vehicle **ret)
{
        if (HasTileRoadType(tile, ROADTYPE_TRAM) != HasBit(e->info.misc_flags, EF_ROAD_TRAM)) return_cmd_error(STR_ERROR_DEPOT_WRONG_DEPOT_TYPE);

        if (flags & DC_EXEC) {
                const RoadVehicleInfo *rvi = &e->u.road;

                RoadVehicle *v = new RoadVehicle();
                *ret = v;
                v->direction = DiagDirToDir(GetGroundDepotDirection(tile));
                v->owner = _current_company;

                v->tile = tile;
                int x = TileX(tile) * TILE_SIZE + TILE_SIZE / 2;
                int y = TileY(tile) * TILE_SIZE + TILE_SIZE / 2;
                v->x_pos = x;
                v->y_pos = y;
                v->z_pos = GetSlopePixelZ(x, y);

                v->state = RVSB_IN_DEPOT;
                v->vehstatus = VS_HIDDEN | VS_STOPPED | VS_DEFPAL;

                v->spritenum = rvi->image_index;
                v->cargo_type = e->GetDefaultCargoType();
                v->cargo_cap = rvi->capacity;
                v->refit_cap = 0;

                v->last_station_visited = INVALID_STATION;
                v->last_loading_station = INVALID_STATION;
                v->engine_type = e->index;
                v->gcache.first_engine = INVALID_ENGINE; // needs to be set before first callback

                v->reliability = e->reliability;
                v->reliability_spd_dec = e->reliability_spd_dec;
                v->max_age = e->GetLifeLengthInDays();
                _new_vehicle_id = v->index;

                v->SetServiceInterval(Company::Get(v->owner)->settings.vehicle.servint_roadveh);

                v->date_of_last_service = _date;
                v->build_year = _cur_year;

                v->cur_image = SPR_IMG_QUERY;
                v->random_bits = VehicleRandomBits();
                v->SetFrontEngine();

                v->roadtype = HasBit(e->info.misc_flags, EF_ROAD_TRAM) ? ROADTYPE_TRAM : ROADTYPE_ROAD;
                v->compatible_roadtypes = RoadTypeToRoadTypes(v->roadtype);
                v->gcache.cached_veh_length = VEHICLE_LENGTH;

                if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) SetBit(v->vehicle_flags, VF_BUILT_AS_PROTOTYPE);
                v->SetServiceIntervalIsPercent(Company::Get(_current_company)->settings.vehicle.servint_ispercent);

                AddArticulatedParts(v);
                v->InvalidateNewGRFCacheOfChain();

                /* Call various callbacks after the whole consist has been constructed */
                for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
                        u->cargo_cap = u->GetEngine()->DetermineCapacity(u);
                        u->refit_cap = 0;
                        v->InvalidateNewGRFCache();
                        u->InvalidateNewGRFCache();
                }
                RoadVehUpdateCache(v);
                /* Initialize cached values for realistic acceleration. */
                if (_settings_game.vehicle.roadveh_acceleration_model != AM_ORIGINAL) v->CargoChanged();

                VehicleUpdatePosition(v);

                CheckConsistencyOfArticulatedVehicle(v);
        }

        return CommandCost();
}

static TileIndex FindClosestRoadDepot(const RoadVehicle *v, bool nearby)
{
        if (IsRoadDepotTile(v->tile) && v->state == DiagDirToDiagTrackdir(ReverseDiagDir(GetGroundDepotDirection(v->tile)))) {
                return v->tile;
        }

        return YapfRoadVehicleFindNearestDepot(v,
                nearby ? _settings_game.pf.yapf.maximum_go_to_depot_penalty : 0);
}

bool RoadVehicle::FindClosestDepot(TileIndex *location, DestinationID *destination, bool *reverse)
{
        TileIndex rfdd = FindClosestRoadDepot(this, false);
        if (rfdd == INVALID_TILE) return false;

        if (location    != NULL) *location    = rfdd;
        if (destination != NULL) *destination = GetDepotIndex(rfdd);

        return true;
}

/**
 * Turn a roadvehicle around.
 * @param tile unused
 * @param flags operation to perform
 * @param p1 vehicle ID to turn
 * @param p2 unused
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdTurnRoadVeh(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
        RoadVehicle *v = RoadVehicle::GetIfValid(p1);
        if (v == NULL) return CMD_ERROR;

        if (!v->IsPrimaryVehicle()) return CMD_ERROR;

        CommandCost ret = CheckOwnership(v->owner);
        if (ret.Failed()) return ret;

        if ((v->vehstatus & VS_STOPPED) ||
                        (v->vehstatus & VS_CRASHED) ||
                        v->breakdown_ctr != 0 ||
                        v->overtaking != 0 ||
                        v->state == RVSB_WORMHOLE ||
                        v->IsInDepot() ||
                        v->current_order.IsType(OT_LOADING)) {
                return CMD_ERROR;
        }

        if (IsNormalRoadTile(v->tile) && GetDisallowedRoadDirections(v->tile) != DRD_NONE) return CMD_ERROR;

        if ((IsTunnelTile(v->tile) || IsBridgeHeadTile(v->tile)) && DirToDiagDir(v->direction) == GetTunnelBridgeDirection(v->tile)) return CMD_ERROR;

        if (flags & DC_EXEC) v->reverse_ctr = 180;

        return CommandCost();
}


void RoadVehicle::MarkDirty()
{
        for (RoadVehicle *v = this; v != NULL; v = v->Next()) {
                v->colourmap = PAL_NONE;
                v->UpdateViewport(true, false);
        }
        this->CargoChanged();
}

void RoadVehicle::UpdateDeltaXY(Direction direction)
{
        static const int8 _delta_xy_table[8][10] = {
                /* y_extent, x_extent, y_offs, x_offs, y_bb_offs, x_bb_offs, y_extent_shorten, x_extent_shorten, y_bb_offs_shorten, x_bb_offs_shorten */
                {3, 3, -1, -1,  0,  0, -1, -1, -1, -1}, // N
                {3, 7, -1, -3,  0, -1,  0, -1,  0,  0}, // NE
                {3, 3, -1, -1,  0,  0,  1, -1,  1, -1}, // E
                {7, 3, -3, -1, -1,  0,  0,  0,  1,  0}, // SE
                {3, 3, -1, -1,  0,  0,  1,  1,  1,  1}, // S
                {3, 7, -1, -3,  0, -1,  0,  0,  0,  1}, // SW
                {3, 3, -1, -1,  0,  0, -1,  1, -1,  1}, // W
                {7, 3, -3, -1, -1,  0, -1,  0,  0,  0}, // NW
        };

        int shorten = VEHICLE_LENGTH - this->gcache.cached_veh_length;
        if (!IsDiagonalDirection(direction)) shorten >>= 1;

        const int8 *bb = _delta_xy_table[direction];
        this->x_bb_offs     = bb[5] + bb[9] * shorten;
        this->y_bb_offs     = bb[4] + bb[8] * shorten;;
        this->x_offs        = bb[3];
        this->y_offs        = bb[2];
        this->x_extent      = bb[1] + bb[7] * shorten;
        this->y_extent      = bb[0] + bb[6] * shorten;
        this->z_extent      = 6;
}

/**
 * Calculates the maximum speed of the vehicle under its current conditions.
 * @return Maximum speed of the vehicle.
 */
inline int RoadVehicle::GetCurrentMaxSpeed() const
{
        int max_speed = this->vcache.cached_max_speed;

        /* Limit speed to 50% while reversing, 75% in curves. */
        for (const RoadVehicle *u = this; u != NULL; u = u->Next()) {
                if (_settings_game.vehicle.roadveh_acceleration_model == AM_REALISTIC) {
                        if (this->state <= RVSB_TRACKDIR_MASK && IsReversingRoadTrackdir((Trackdir)this->state)) {
                                max_speed = this->vcache.cached_max_speed / 2;
                                break;
                        } else if ((u->direction & 1) == 0) {
                                max_speed = this->vcache.cached_max_speed * 3 / 4;
                        }
                }

                /* Vehicle is on the middle part of a bridge. */
                if (u->state == RVSB_WORMHOLE && !(u->vehstatus & VS_HIDDEN)) {
                        max_speed = min(max_speed, GetBridgeSpec(GetRoadBridgeType(u->tile))->speed * 2);
                }
        }

        return min(max_speed, this->current_order.max_speed * 2);
}

/**
 * Delete last vehicle of a chain road vehicles.
 * @param v First roadvehicle.
 */
static void DeleteLastRoadVeh(RoadVehicle *v)
{
        RoadVehicle *first = v->First();
        Vehicle *u = v;
        for (; v->Next() != NULL; v = v->Next()) u = v;
        u->SetNext(NULL);
        v->last_station_visited = first->last_station_visited; // for PreDestructor

        /* Only leave the road stop when we're really gone. */
        if (IsInsideMM(v->state, RVSB_IN_ROAD_STOP, RVSB_IN_ROAD_STOP_END)) RoadStop::GetByTile(v->tile, GetRoadStopType(v->tile))->Leave(v);

        delete v;
}

static void RoadVehSetRandomDirection(RoadVehicle *v)
{
        static const DirDiff delta[] = {
                DIRDIFF_45LEFT, DIRDIFF_SAME, DIRDIFF_SAME, DIRDIFF_45RIGHT
        };

        do {
                uint32 r = Random();

                v->direction = ChangeDir(v->direction, delta[r & 3]);
                v->UpdateViewport(true, true);
        } while ((v = v->Next()) != NULL);
}

/**
 * Road vehicle chain has crashed.
 * @param v First roadvehicle.
 * @return whether the chain still exists.
 */
static bool RoadVehIsCrashed(RoadVehicle *v)
{
        v->crashed_ctr++;
        if (v->crashed_ctr == 2) {
                CreateEffectVehicleRel(v, 4, 4, 8, EV_EXPLOSION_LARGE);
        } else if (v->crashed_ctr <= 45) {
                if ((v->tick_counter & 7) == 0) RoadVehSetRandomDirection(v);
        } else if (v->crashed_ctr >= 2220 && !(v->tick_counter & 0x1F)) {
                bool ret = v->Next() != NULL;
                DeleteLastRoadVeh(v);
                return ret;
        }

        return true;
}

/**
 * Check routine whether a road and a train vehicle have collided.
 * @param v    %Train vehicle to test.
 * @param data Road vehicle to test.
 * @return %Train vehicle if the vehicles collided, else \c NULL.
 */
static Vehicle *EnumCheckRoadVehCrashTrain(Vehicle *v, void *data)
{
        const Vehicle *u = (Vehicle*)data;

        return (v->type == VEH_TRAIN &&
                        abs(v->z_pos - u->z_pos) <= 6 &&
                        abs(v->x_pos - u->x_pos) <= 4 &&
                        abs(v->y_pos - u->y_pos) <= 4) ? v : NULL;
}

uint RoadVehicle::Crash(bool flooded)
{
        uint pass = this->GroundVehicleBase::Crash(flooded);
        if (this->IsFrontEngine()) {
                pass += 1; // driver

                /* If we're in a drive through road stop we ought to leave it */
                if (IsInsideMM(this->state, RVSB_IN_DT_ROAD_STOP, RVSB_IN_DT_ROAD_STOP_END)) {
                        RoadStop::GetByTile(this->tile, GetRoadStopType(this->tile))->Leave(this);
                }
        }
        this->crashed_ctr = flooded ? 2000 : 1; // max 2220, disappear pretty fast when flooded
        return pass;
}

static void RoadVehCrash(RoadVehicle *v)
{
        uint pass = v->Crash();

        AI::NewEvent(v->owner, new ScriptEventVehicleCrashed(v->index, v->tile, ScriptEventVehicleCrashed::CRASH_RV_LEVEL_CROSSING));
        Game::NewEvent(new ScriptEventVehicleCrashed(v->index, v->tile, ScriptEventVehicleCrashed::CRASH_RV_LEVEL_CROSSING));

        SetDParam(0, pass);
        AddVehicleNewsItem(
                (pass == 1) ?
                        STR_NEWS_ROAD_VEHICLE_CRASH_DRIVER : STR_NEWS_ROAD_VEHICLE_CRASH,
                NT_ACCIDENT,
                v->index
        );

        ModifyStationRatingAround(v->tile, v->owner, -160, 22);
        if (_settings_client.sound.disaster) SndPlayVehicleFx(SND_12_EXPLOSION, v);
}

static bool RoadVehCheckTrainCrash(RoadVehicle *v)
{
        for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
                if (u->state == RVSB_WORMHOLE) continue;

                TileIndex tile = u->tile;

                if (!IsLevelCrossingTile(tile)) continue;

                if (HasVehicleOnPosXY(v->x_pos, v->y_pos, u, EnumCheckRoadVehCrashTrain)) {
                        RoadVehCrash(v);
                        return true;
                }
        }

        return false;
}

TileIndex RoadVehicle::GetOrderStationLocation(StationID station)
{
        if (station == this->last_station_visited) this->last_station_visited = INVALID_STATION;

        const Station *st = Station::Get(station);
        if (!CanVehicleUseStation(this, st)) {
                /* There is no stop left at the station, so don't even TRY to go there */
                this->IncrementRealOrderIndex();
                return 0;
        }

        return st->xy;
}

static void StartRoadVehSound(const RoadVehicle *v)
{
        if (!PlayVehicleSound(v, VSE_START)) {
                SoundID s = RoadVehInfo(v->engine_type)->sfx;
                if (s == SND_19_BUS_START_PULL_AWAY && (v->tick_counter & 3) == 0) {
                        s = SND_1A_BUS_START_PULL_AWAY_WITH_HORN;
                }
                SndPlayVehicleFx(s, v);
        }
}

struct RoadVehFindData {
        int x;
        int y;
        const Vehicle *veh;
        Vehicle *best;
        uint best_diff;
        Direction dir;
};

static void RoadVehFindCloseToCheck (RoadVehFindData *rvf, Vehicle *v)
{
        static const int8 dist_x[] = { -4, -8, -4, -1, 4, 8, 4, 1 };
        static const int8 dist_y[] = { -4, -1, 4, 8, 4, 1, -4, -8 };

        if (v->type == VEH_ROAD &&
                        !v->IsInDepot() &&
                        abs(v->z_pos - rvf->veh->z_pos) < 6 &&
                        v->direction == rvf->dir &&
                        rvf->veh->First() != v->First()) {

                short x_diff = v->x_pos - rvf->x;
                short y_diff = v->y_pos - rvf->y;

                if ((dist_x[v->direction] > 0 ?
                                        (x_diff >= 0 && x_diff < dist_x[v->direction]) :
                                        (x_diff <= 0 && x_diff > dist_x[v->direction])) &&
                                (dist_y[v->direction] > 0 ?
                                        (y_diff >= 0 && y_diff < dist_y[v->direction]) :
                                        (y_diff <= 0 && y_diff > dist_y[v->direction]))) {
                        uint diff = abs(x_diff) + abs(y_diff);

                        if (diff < rvf->best_diff || (diff == rvf->best_diff && v->index < rvf->best->index)) {
                                rvf->best = v;
                                rvf->best_diff = diff;
                        }
                }
        }
}

static Vehicle *EnumCheckRoadVehClose(Vehicle *v, void *data)
{
        RoadVehFindCloseToCheck ((RoadVehFindData*)data, v);

        return NULL;
}

static RoadVehicle *RoadVehFindCloseTo(RoadVehicle *v, int x, int y, Direction dir, bool update_blocked_ctr = true)
{
        RoadVehFindData rvf;
        RoadVehicle *front = v->First();

        if (front->reverse_ctr != 0) return NULL;

        rvf.x = x;
        rvf.y = y;
        rvf.dir = dir;
        rvf.veh = v;
        rvf.best_diff = UINT_MAX;

        if (front->state == RVSB_WORMHOLE) {
                VehicleTileIterator iter1 (v->tile);
                while (!iter1.finished()) {
                        RoadVehFindCloseToCheck (&rvf, iter1.next());
                }
                VehicleTileIterator iter2 (GetOtherTunnelBridgeEnd(v->tile));
                while (!iter2.finished()) {
                        RoadVehFindCloseToCheck (&rvf, iter2.next());
                }
        } else {
                FindVehicleOnPosXY(x, y, &rvf, EnumCheckRoadVehClose);
        }

        /* This code protects a roadvehicle from being blocked for ever
         * If more than 1480 / 74 days a road vehicle is blocked, it will
         * drive just through it. The ultimate backup-code of TTD.
         * It can be disabled. */
        if (rvf.best_diff == UINT_MAX) {
                front->blocked_ctr = 0;
                return NULL;
        }

        if (update_blocked_ctr && ++front->blocked_ctr > 1480) return NULL;

        return RoadVehicle::From(rvf.best);
}

/**
 * A road vehicle arrives at a station. If it is the first time, create a news item.
 * @param v  Road vehicle that arrived.
 * @param st Station where the road vehicle arrived.
 */
static void RoadVehArrivesAt(const RoadVehicle *v, Station *st)
{
        if (v->IsBus()) {
                /* Check if station was ever visited before */
                if (!(st->had_vehicle_of_type & HVOT_BUS)) {
                        st->had_vehicle_of_type |= HVOT_BUS;
                        SetDParam(0, st->index);
                        AddVehicleNewsItem(
                                v->roadtype == ROADTYPE_ROAD ? STR_NEWS_FIRST_BUS_ARRIVAL : STR_NEWS_FIRST_PASSENGER_TRAM_ARRIVAL,
                                (v->owner == _local_company) ? NT_ARRIVAL_COMPANY : NT_ARRIVAL_OTHER,
                                v->index,
                                st->index
                        );
                        AI::NewEvent(v->owner, new ScriptEventStationFirstVehicle(st->index, v->index));
                        Game::NewEvent(new ScriptEventStationFirstVehicle(st->index, v->index));
                }
        } else {
                /* Check if station was ever visited before */
                if (!(st->had_vehicle_of_type & HVOT_TRUCK)) {
                        st->had_vehicle_of_type |= HVOT_TRUCK;
                        SetDParam(0, st->index);
                        AddVehicleNewsItem(
                                v->roadtype == ROADTYPE_ROAD ? STR_NEWS_FIRST_TRUCK_ARRIVAL : STR_NEWS_FIRST_CARGO_TRAM_ARRIVAL,
                                (v->owner == _local_company) ? NT_ARRIVAL_COMPANY : NT_ARRIVAL_OTHER,
                                v->index,
                                st->index
                        );
                        AI::NewEvent(v->owner, new ScriptEventStationFirstVehicle(st->index, v->index));
                        Game::NewEvent(new ScriptEventStationFirstVehicle(st->index, v->index));
                }
        }
}

/**
 * This function looks at the vehicle and updates its speed (cur_speed
 * and subspeed) variables. Furthermore, it returns the distance that
 * the vehicle can drive this tick. #Vehicle::GetAdvanceDistance() determines
 * the distance to drive before moving a step on the map.
 * @return distance to drive.
 */
int RoadVehicle::UpdateSpeed()
{
        switch (_settings_game.vehicle.roadveh_acceleration_model) {
                default: NOT_REACHED();
                case AM_ORIGINAL:
                        return this->DoUpdateSpeed(this->overtaking != 0 ? 512 : 256, 0, this->GetCurrentMaxSpeed());

                case AM_REALISTIC:
                        return this->DoUpdateSpeed(this->GetAcceleration() + (this->overtaking != 0 ? 256 : 0), this->GetAccelerationStatus() == AS_BRAKE ? 0 : 4, this->GetCurrentMaxSpeed());
        }
}


/** The returned bits of VehicleEnterTile. */
enum VehicleEnterTileStatus {
        VETS_CONTINUE         = 0, ///< The vehicle can continue normally
        VETS_ENTERED_WORMHOLE = 1, ///< The vehicle either entered a bridge, tunnel or depot tile
        VETS_CANNOT_ENTER     = 2, ///< The vehicle cannot enter the tile
};
DECLARE_ENUM_AS_BIT_SET(VehicleEnterTileStatus)

static VehicleEnterTileStatus RoadVehEnter_Road(RoadVehicle *v, TileIndex tile, int x, int y)
{
        if (IsTileSubtype(tile, TT_TRACK)) return VETS_CONTINUE;

        assert(abs((int)(GetSlopePixelZ(x, y) - v->z_pos)) < 3);

        /* modify speed of vehicle */
        uint16 spd = GetBridgeSpec(GetRoadBridgeType(tile))->speed * 2;
        Vehicle *first = v->First();
        first->cur_speed = min(first->cur_speed, spd);

        return VETS_CONTINUE;
}

extern const byte _tunnel_visibility_frame[DIAGDIR_END];

static VehicleEnterTileStatus RoadVehEnter_Misc(RoadVehicle *u, TileIndex tile, int x, int y)
{
        switch (GetTileSubtype(tile)) {
                default: break;

                case TT_MISC_TUNNEL: {
                        assert(abs((int)GetSlopePixelZ(x, y) - u->z_pos) < 3);

                        /* Direction into the wormhole */
                        const DiagDirection dir = GetTunnelBridgeDirection(tile);

                        if (u->direction == DiagDirToDir(dir)) {
                                uint frame = DistanceFromTileEdge(ReverseDiagDir(dir), x & 0xF, y & 0xF);
                                if (frame == _tunnel_visibility_frame[dir]) {
                                        /* Frame should be equal to the next frame number in the RV's movement */
                                        assert((int)frame == u->frame + 1);
                                        u->vehstatus |= VS_HIDDEN;
                                }
                        } else if (u->direction == ReverseDir(DiagDirToDir(dir))) {
                                uint frame = DistanceFromTileEdge(dir, x & 0xF, y & 0xF);
                                if (frame == TILE_SIZE - _tunnel_visibility_frame[dir]) {
                                        assert((int)frame == u->frame + 1);
                                        u->vehstatus &= ~VS_HIDDEN;
                                }
                        }

                        break;
                }

                case TT_MISC_DEPOT:
                        if (!IsRoadDepot(tile)) break;

                        if (u->frame == RVC_DEPOT_STOP_FRAME &&
                                        u->state == DiagDirToDiagTrackdir(ReverseDiagDir(GetGroundDepotDirection(tile)))) {
                                u->state = RVSB_IN_DEPOT;
                                u->vehstatus |= VS_HIDDEN;
                                u->direction = ReverseDir(u->direction);
                                if (u->Next() == NULL) VehicleEnterDepot(u->First());
                                u->tile = tile;

                                InvalidateWindowData(WC_VEHICLE_DEPOT, u->tile);
                                return VETS_ENTERED_WORMHOLE;
                        }

                        break;
        }

        return VETS_CONTINUE;
}

static VehicleEnterTileStatus RoadVehEnter_Station(RoadVehicle *v, TileIndex tile, int x, int y)
{
        if (v->state < RVSB_IN_ROAD_STOP && !IsReversingRoadTrackdir((Trackdir)v->state) && v->frame == 0) {
                if (IsRoadStop(tile) && v->IsFrontEngine()) {
                        /* Attempt to allocate a parking bay in a road stop */
                        return RoadStop::GetByTile(tile, GetRoadStopType(tile))->Enter(v) ? VETS_CONTINUE : VETS_CANNOT_ENTER;
                }
        }

        return VETS_CONTINUE;
}

/**
 * Call the tile callback function for a road vehicle entering a tile
 * @param v    Road vehicle entering the tile
 * @param tile Tile entered
 * @param x    X position
 * @param y    Y position
 * @return Some meta-data over the to be entered tile.
 * @see VehicleEnterTileStatus to see what the bits in the return value mean.
 */
static VehicleEnterTileStatus RoadVehEnterTile(RoadVehicle *v, TileIndex tile, int x, int y)
{
        switch (GetTileType(tile)) {
                default: NOT_REACHED();

                case TT_ROAD:
                        return RoadVehEnter_Road(v, tile, x, y);

                case TT_MISC:
                        return RoadVehEnter_Misc(v, tile, x, y);

                case TT_STATION:
                        return RoadVehEnter_Station(v, tile, x, y);
        }
}

static Direction RoadVehGetNewDirection(const RoadVehicle *v, int x, int y)
{
        static const Direction _roadveh_new_dir[] = {
                DIR_N , DIR_NW, DIR_W , INVALID_DIR,
                DIR_NE, DIR_N , DIR_SW, INVALID_DIR,
                DIR_E , DIR_SE, DIR_S
        };

        x = x - v->x_pos + 1;
        y = y - v->y_pos + 1;

        if ((uint)x > 2 || (uint)y > 2) return v->direction;
        return _roadveh_new_dir[y * 4 + x];
}

static Direction RoadVehGetSlidingDirection(const RoadVehicle *v, int x, int y)
{
        Direction new_dir = RoadVehGetNewDirection(v, x, y);
        Direction old_dir = v->direction;
        DirDiff delta;

        if (new_dir == old_dir) return old_dir;
        delta = (DirDifference(new_dir, old_dir) > DIRDIFF_REVERSE ? DIRDIFF_45LEFT : DIRDIFF_45RIGHT);
        return ChangeDir(old_dir, delta);
}

struct OvertakeData {
        const RoadVehicle *u;
        const RoadVehicle *v;
        TileIndex tile;
        Trackdir trackdir;
};

/**
 * Check if overtaking is possible on a piece of track
 *
 * @param od Information about the tile and the involved vehicles
 * @return true if we have to abort overtaking
 */
static bool CheckRoadBlockedForOvertaking(OvertakeData *od)
{
        TrackStatus ts = GetTileRoadStatus(od->tile, od->v->compatible_roadtypes);
        TrackdirBits trackdirbits = TrackStatusToTrackdirBits(ts);
        TrackdirBits red_signals = TrackStatusToRedSignals(ts); // barred level crossing
        TrackBits trackbits = TrackdirBitsToTrackBits(trackdirbits);

        /* Track does not continue along overtaking direction || track has junction || levelcrossing is barred */
        if (!HasBit(trackdirbits, od->trackdir) || (trackbits & ~TRACK_BIT_CROSS) || (red_signals != TRACKDIR_BIT_NONE)) return true;

        /* Are there more vehicles on the tile except the two vehicles involved in overtaking */
        VehicleTileFinder iter (od->tile);
        while (!iter.finished()) {
                Vehicle *v = iter.next();
                if (v->type == VEH_ROAD && v->First() == v && v != od->u && v != od->v) {
                        iter.set_found();
                }
        }
        return iter.was_found();
}

static void RoadVehCheckOvertake(RoadVehicle *v, RoadVehicle *u)
{
        OvertakeData od;

        od.v = v;
        od.u = u;

        if (u->vcache.cached_max_speed >= v->vcache.cached_max_speed &&
                        !(u->vehstatus & VS_STOPPED) &&
                        u->cur_speed != 0) {
                return;
        }

        /* Trams can't overtake other trams */
        if (v->roadtype == ROADTYPE_TRAM) return;

        /* Don't overtake in stations */
        if (IsStationTile(v->tile) || IsStationTile(u->tile)) return;

        /* For now, articulated road vehicles can't overtake anything. */
        if (v->HasArticulatedPart()) return;

        /* Vehicles are not driving in same direction || direction is not a diagonal direction */
        if (v->direction != u->direction || !(v->direction & 1)) return;

        /* Check if vehicle is in a road stop, depot, tunnel or bridge or not on a straight road */
        if (v->state >= RVSB_IN_ROAD_STOP || !IsStraightRoadTrackdir((Trackdir)(v->state & RVSB_TRACKDIR_MASK))) return;

        od.trackdir = DiagDirToDiagTrackdir(DirToDiagDir(v->direction));

        /* Are the current and the next tile suitable for overtaking?
         *  - Does the track continue along od.trackdir
         *  - No junctions
         *  - No barred levelcrossing
         *  - No other vehicles in the way
         */
        od.tile = v->tile;
        if (CheckRoadBlockedForOvertaking(&od)) return;

        od.tile = v->tile + TileOffsByDiagDir(DirToDiagDir(v->direction));
        if (CheckRoadBlockedForOvertaking(&od)) return;

        /* When the vehicle in front of us is stopped we may only take
         * half the time to pass it than when the vehicle is moving. */
        v->overtaking_ctr = (od.u->cur_speed == 0 || (od.u->vehstatus & VS_STOPPED)) ? RV_OVERTAKE_TIMEOUT / 2 : 0;
        v->overtaking = 1;
}

static void RoadZPosAffectSpeed(RoadVehicle *v, byte old_z)
{
        if (old_z == v->z_pos || _settings_game.vehicle.roadveh_acceleration_model != AM_ORIGINAL) return;

        if (old_z < v->z_pos) {
                v->cur_speed = v->cur_speed * 232 / 256; // slow down by ~10%
        } else {
                uint16 spd = v->cur_speed + 2;
                if (spd <= v->vcache.cached_max_speed) v->cur_speed = spd;
        }
}

static int PickRandomBit(uint bits)
{
        uint i;
        uint num = RandomRange(CountBits(bits));

        for (i = 0; !(bits & 1) || (int)--num >= 0; bits >>= 1, i++) {}
        return i;
}

/**
 * Returns direction to for a road vehicle to take or
 * INVALID_TRACKDIR if the direction is currently blocked
 * @param v        the Vehicle to do the pathfinding for
 * @param tile     the where to start the pathfinding
 * @param enterdir the direction the vehicle enters the tile from
 * @return the Trackdir to take
 */
static Trackdir RoadFindPathToDest(RoadVehicle *v, TileIndex tile, DiagDirection enterdir)
{
#define return_track(x) { best_track = (Trackdir)x; goto found_best_track; }

        TileIndex desttile;
        Trackdir best_track;
        bool path_found = true;

        TrackStatus ts = GetTileRoadStatus(tile, v->compatible_roadtypes);
        TrackdirBits red_signals = TrackStatusToRedSignals(ts); // crossing
        TrackdirBits trackdirs = TrackStatusToTrackdirBits(ts);

        if (IsRoadDepotTile(tile)) {
                if ((!IsTileOwner(tile, v->owner) || GetGroundDepotDirection(tile) == enterdir || (GetRoadTypes(tile) & v->compatible_roadtypes) == 0)) {
                        /* Road depot owned by another company or with the wrong orientation */
                        trackdirs = TRACKDIR_BIT_NONE;
                }
        } else if (IsStationTile(tile) && IsStandardRoadStopTile(tile)) {
                /* Standard road stop (drive-through stops are treated as normal road) */

                if (!IsTileOwner(tile, v->owner) || GetRoadStopDir(tile) == enterdir || v->HasArticulatedPart()) {
                        /* different station owner or wrong orientation or the vehicle has articulated parts */
                        trackdirs = TRACKDIR_BIT_NONE;
                } else {
                        /* Our station */
                        RoadStopType rstype = v->IsBus() ? ROADSTOP_BUS : ROADSTOP_TRUCK;

                        if (GetRoadStopType(tile) != rstype) {
                                /* Wrong station type */
                                trackdirs = TRACKDIR_BIT_NONE;
                        } else {
                                /* Proper station type, check if there is free loading bay */
                                if (!_settings_game.pf.roadveh_queue && IsStandardRoadStopTile(tile) &&
                                                !RoadStop::GetByTile(tile, rstype)->HasFreeBay()) {
                                        /* Station is full and RV queuing is off */
                                        trackdirs = TRACKDIR_BIT_NONE;
                                }
                        }
                }
        }
        /* The above lookups should be moved to GetTileTrackStatus in the
         * future, but that requires more changes to the pathfinder and other
         * stuff, probably even more arguments to GTTS.
         */

        /* Remove tracks unreachable from the enter dir */
        trackdirs &= DiagdirReachesTrackdirs(enterdir);
        if (trackdirs == TRACKDIR_BIT_NONE) {
                /* No reachable tracks, so we'll reverse */
                return_track(_road_reverse_table[enterdir]);
        }

        if (v->reverse_ctr != 0) {
                bool reverse = true;
                if (v->roadtype == ROADTYPE_TRAM) {
                        /* Trams may only reverse on a tile if it contains at least the straight
                         * trackbits or when it is a valid turning tile (i.e. one roadbit) */
                        RoadBits rb = GetAnyRoadBits(tile, ROADTYPE_TRAM);
                        RoadBits straight = AxisToRoadBits(DiagDirToAxis(enterdir));
                        reverse = ((rb & straight) == straight) ||
                                  (rb == DiagDirToRoadBits(enterdir));
                }
                if (reverse) {
                        v->reverse_ctr = 0;
                        if (v->tile != tile) {
                                return_track(_road_reverse_table[enterdir]);
                        }
                }
        }

        desttile = v->dest_tile;
        if (desttile == 0) {
                /* We've got no destination, pick a random track */
                return_track(PickRandomBit(trackdirs));
        }

        /* Only one track to choose between? */
        if (KillFirstBit(trackdirs) == TRACKDIR_BIT_NONE) {
                return_track(FindFirstBit2x64(trackdirs));
        }

        best_track = YapfRoadVehicleChooseTrack(v, tile, enterdir, trackdirs, path_found);
        v->HandlePathfindingResult(path_found);

found_best_track:;

        if (HasBit(red_signals, best_track)) return INVALID_TRACKDIR;

        return best_track;
}

struct RoadDriveEntry {
        byte x, y;
};

#include "table/roadveh_movement.h"

static bool RoadVehLeaveDepot(RoadVehicle *v, bool first)
{
        /* Don't leave unless v and following wagons are in the depot. */
        for (const RoadVehicle *u = v; u != NULL; u = u->Next()) {
                if (u->state != RVSB_IN_DEPOT || u->tile != v->tile) return false;
        }

        DiagDirection dir = GetGroundDepotDirection(v->tile);
        v->direction = DiagDirToDir(dir);

        Trackdir tdir = DiagDirToDiagTrackdir(dir);
        const RoadDriveEntry *rdp = _road_drive_data[_settings_game.vehicle.road_side][tdir];

        int x = TileX(v->tile) * TILE_SIZE + rdp[RVC_DEPOT_START_FRAME].x;
        int y = TileY(v->tile) * TILE_SIZE + rdp[RVC_DEPOT_START_FRAME].y;

        if (first) {
                /* We are leaving a depot, but have to go to the exact same one; re-enter */
                if (v->current_order.IsType(OT_GOTO_DEPOT) && v->tile == v->dest_tile) {
                        VehicleEnterDepot(v);
                        return true;
                }

                if (RoadVehFindCloseTo(v, x, y, v->direction, false) != NULL) return true;

                VehicleServiceInDepot(v);

                StartRoadVehSound(v);

                /* Vehicle is about to leave a depot */
                v->cur_speed = 0;
        }

        v->vehstatus &= ~VS_HIDDEN;
        v->state = tdir;
        v->frame = RVC_DEPOT_START_FRAME;

        v->x_pos = x;
        v->y_pos = y;
        VehicleUpdatePosition(v);
        v->UpdateInclination(true, true);

        InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);

        return true;
}

static Trackdir FollowPreviousRoadVehicle(const RoadVehicle *v, const RoadVehicle *prev, TileIndex tile, DiagDirection entry_dir)
{
        Trackdir dir;
        if (prev->tile != tile) {
                /*
                 * The previous vehicle has already left the tile; follow
                 * the trackdir that heads in its direction.
                 */
                DiagDirection exitdir = DiagdirBetweenTiles(tile, prev->tile);
                assert(IsValidDiagDirection(exitdir));
                dir = EnterdirExitdirToTrackdir(entry_dir, exitdir);
        } else {
                byte prev_state = prev->state;

                assert(prev_state != RVSB_WORMHOLE);

                if (prev_state == RVSB_IN_DEPOT) {
                        dir = DiagDirToDiagTrackdir(ReverseDiagDir(GetGroundDepotDirection(tile)));
                } else if (HasBit(prev_state, RVS_IN_DT_ROAD_STOP)) {
                        dir = (Trackdir)(prev_state & RVSB_ROAD_STOP_TRACKDIR_MASK);
                } else {
                        assert(prev_state < TRACKDIR_END);
                        dir = (Trackdir)prev_state;

                        /* Some bends are so short that the vehicle ahead has
                         * already left the tile when we reach it; this is
                         * caught by the conditional prev->tile != tile above.
                         * However, if the vehicle ahead turned around at the
                         * tile edge instead of moving forward, it is still
                         * in this tile but has switched to a reversing
                         * trackdir. In such a case, we must not use its
                         * trackdir, but head in the direction of the tile
                         * side at which it is reversing. */
                        if (IsReversingRoadTrackdir(dir)) {
                                DiagDirection side = TrackdirToExitdir(dir);
                                assert (entry_dir != side);
                                side = ReverseDiagDir(side);
                                if (entry_dir != side) dir = EnterdirExitdirToTrackdir(entry_dir, side);
                        }
                }
        }

        /* Do some sanity checking. */
        if (!IsReversingRoadTrackdir(dir)) {
                static const RoadBits required_roadbits[TRACK_END] = {
                        ROAD_X, ROAD_Y, ROAD_N, ROAD_S, ROAD_W, ROAD_E,
                };

                RoadBits required = required_roadbits[TrackdirToTrack(dir)];

                assert((required & GetAnyRoadBits(tile, v->roadtype, true)) != ROAD_NONE);
        }

        return dir;
}

/**
 * Can a tram track build without destruction on the given tile?
 * @param c the company that would be building the tram tracks
 * @param t the tile to build on.
 * @param r the road bits needed.
 * @return true when a track track can be build on 't'
 */
static bool CanBuildTramTrackOnTile(CompanyID c, TileIndex t, RoadBits r)
{
        /* The 'current' company is not necessarily the owner of the vehicle. */
        Backup<CompanyByte> cur_company(_current_company, c, FILE_LINE);

        CommandCost ret = DoCommand(t, ROADTYPE_TRAM << 4 | r, 0, DC_NO_WATER, CMD_BUILD_ROAD);

        cur_company.Restore();
        return ret.Succeeded();
}

/**
 * Make a road vehicle enter a wormhole.
 * @param v The road vehicle
 * @param end The other wormhole end
 * @param is_bridge Whether the wormhole is a bridge (as opposed to a tunnel)
 * @return Whether the vehicle moved at all
 * @pre The vehicle must be at the last frame of a wormhole head tile
 */
static bool IndividualRoadVehicleControllerEnterWormhole(RoadVehicle *v, TileIndex end, bool is_bridge)
{
        VehiclePos gp = GetNewVehiclePos(v);

        /* this should really bring us to a new virtual tile */
        assert(gp.new_tile != v->tile);

        if (v->IsFrontEngine()) {
                const Vehicle *u = RoadVehFindCloseTo (v, gp.x, gp.y, v->direction);
                if (u != NULL) {
                        v->cur_speed = u->First()->cur_speed;
                        return false;
                }
        }

        v->tile  = end;
        v->state = RVSB_WORMHOLE;
        v->x_pos = gp.x;
        v->y_pos = gp.y;

        if (is_bridge) {
                ClrBit(v->gv_flags, GVF_GOINGUP_BIT);
                ClrBit(v->gv_flags, GVF_GOINGDOWN_BIT);

                RoadVehicle *first = v->First();
                first->cur_speed = min(first->cur_speed, GetBridgeSpec(GetRoadBridgeType(end))->speed * 2);

                VehicleUpdatePositionAndViewport(v);
        } else {
                VehicleUpdatePosition(v);
        }

        return true;
}

static bool IndividualRoadVehicleController(RoadVehicle *v, const RoadVehicle *prev)
{
        if (v->overtaking != 0)  {
                if (IsStationTile(v->tile)) {
                        /* Force us to be not overtaking! */
                        v->overtaking = 0;
                } else if (++v->overtaking_ctr >= RV_OVERTAKE_TIMEOUT) {
                        /* If overtaking just aborts at a random moment, we can have a out-of-bound problem,
                         *  if the vehicle started a corner. To protect that, only allow an abort of
                         *  overtake if we are on straight roads */
                        if (v->state < RVSB_IN_ROAD_STOP && IsStraightRoadTrackdir((Trackdir)v->state)) {
                                v->overtaking = 0;
                        }
                }
        }

        /* If this vehicle is in a depot and we've reached this point it must be
         * one of the articulated parts. It will stay in the depot until activated
         * by the previous vehicle in the chain when it gets to the right place. */
        if (v->IsInDepot()) return true;

        RoadDriveEntry rd;
        TileIndex tile; // only used when entering a new tile

        if (v->state == RVSB_WORMHOLE) {
                /* Vehicle is entering a depot or is on a bridge or in a tunnel */
                VehiclePos gp = GetNewVehiclePos(v);

                if (v->IsFrontEngine()) {
                        const Vehicle *u = RoadVehFindCloseTo(v, gp.x, gp.y, v->direction);
                        if (u != NULL) {
                                v->cur_speed = u->First()->cur_speed;
                                return false;
                        }
                }

                if (gp.new_tile != v->tile) {
                        /* Still in the wormhole */
                        v->x_pos = gp.x;
                        v->y_pos = gp.y;
                        VehicleUpdatePosition(v);
                        if ((v->vehstatus & VS_HIDDEN) == 0) VehicleUpdateViewport(v, true);
                        return true;
                }

                /* Vehicle has just exited a bridge or tunnel */
                rd.x = RDE_NEXT_TILE;
                rd.y = ReverseDiagDir(GetTunnelBridgeDirection(gp.new_tile));
                tile = gp.new_tile;
        } else {
                /* Get move position data for next frame.
                 * For a drive-through road stop use 'straight road' move data.
                 * In this case v->state is masked to give the road stop entry direction. */
                rd = _road_drive_data[_settings_game.vehicle.road_side ^ v->overtaking]
                        [HasBit(v->state, RVS_IN_DT_ROAD_STOP) ? (v->state & RVSB_ROAD_STOP_TRACKDIR_MASK) : v->state]
                        [v->frame + 1];

                if (rd.x == RDE_NEXT_TILE) {
                        DiagDirection enterdir = (DiagDirection)(rd.y);
                        tile = v->tile + TileOffsByDiagDir(enterdir);

                        if (IsTunnelTile(v->tile) && GetTunnelBridgeDirection(v->tile) == enterdir) {
                                TileIndex end_tile = GetOtherTunnelEnd(v->tile);
                                if (end_tile != tile) {
                                        /* Entering a tunnel */
                                        return IndividualRoadVehicleControllerEnterWormhole (v, end_tile, false);
                                }
                        } else if (IsRoadBridgeTile(v->tile) && GetTunnelBridgeDirection(v->tile) == enterdir) {
                                TileIndex end_tile = GetOtherBridgeEnd(v->tile);
                                if (end_tile != tile) {
                                        /* Entering a bridge */
                                        return IndividualRoadVehicleControllerEnterWormhole (v, end_tile, true);
                                }
                        }
                }
        }

        if (rd.x == RDE_NEXT_TILE) {
                DiagDirection enterdir = (DiagDirection)(rd.y);

                Trackdir dir;

                if (v->IsFrontEngine()) {
                        /* If this is the front engine, look for the right path. */
                        dir = RoadFindPathToDest(v, tile, enterdir);

                        if (dir == INVALID_TRACKDIR) {
                                v->cur_speed = 0;
                                return false;
                        }
                } else {
                        dir = FollowPreviousRoadVehicle(v, prev, tile, enterdir);
                }

                uint start_frame = RVC_DEFAULT_START_FRAME;
                if (IsReversingRoadTrackdir(dir)) {
                        /* When turning around we can't be overtaking. */
                        v->overtaking = 0;
                        bool use_long_corner;

                        /* Turning around */
                        if (v->roadtype == ROADTYPE_ROAD) {
                                /* Not a tram. */
                                if (IsNormalRoadTile(v->tile) && GetDisallowedRoadDirections(v->tile) != DRD_NONE) {
                                        v->cur_speed = 0;
                                        return false;
                                }
                                use_long_corner = false;
                        } else if (v->IsFrontEngine()) {
                                /* Tram front vehicle. */

                                /* Determine the road bits the tram needs to be able to turn around
                                 * using the 'big' corner loop. */
                                RoadBits needed;
                                switch (dir) {
                                        default: NOT_REACHED();
                                        case TRACKDIR_RVREV_NE: needed = ROAD_SW; break;
                                        case TRACKDIR_RVREV_SE: needed = ROAD_NW; break;
                                        case TRACKDIR_RVREV_SW: needed = ROAD_NE; break;
                                        case TRACKDIR_RVREV_NW: needed = ROAD_SE; break;
                                }
                                if (IsNormalRoadTile(tile) && !HasRoadWorks(tile) &&
                                                (needed & GetRoadBits(tile, ROADTYPE_TRAM)) != ROAD_NONE) {
                                        /*
                                         * Taking the 'big' corner for trams only happens when
                                         * the front of the tram can drive over the next tile.
                                         */
                                        use_long_corner = true;
                                } else if (!CanBuildTramTrackOnTile(v->owner, tile, needed) || ((~needed & GetAnyRoadBits(v->tile, ROADTYPE_TRAM, false)) == ROAD_NONE)) {
                                        /*
                                         * Taking the 'small' corner for trams only happens when
                                         * the company cannot build on the next tile.
                                         */
                                        use_long_corner = false;
                                } else {
                                        /* The company can build on the next tile, so wait till (s)he does. */
                                        v->cur_speed = 0;
                                        return false;
                                }
                        } else {
                                /* Tram, not front vehicle. Just follow the previous vehicle. */
                                use_long_corner = (v->Previous()->tile == tile);
                        }

                        if (use_long_corner) {
                                start_frame = RVC_LONG_TURN_START_FRAME;
                        } else {
                                /*
                                 * The 'small' corner means that the vehicle is on the end of a
                                 * tram track and needs to start turning there. It therefore
                                 * does not go to the next tile, so that needs to be fixed.
                                 */
                                tile = v->tile;
                                start_frame = RVC_SHORT_TURN_START_FRAME;
                        }
                }

                /* Get position data for first frame on the new tile */
                const RoadDriveEntry *rdp = _road_drive_data[_settings_game.vehicle.road_side ^ v->overtaking][dir];

                int x = TileX(tile) * TILE_SIZE + rdp[start_frame].x;
                int y = TileY(tile) * TILE_SIZE + rdp[start_frame].y;

                Direction new_dir = RoadVehGetSlidingDirection(v, x, y);
                if (v->IsFrontEngine()) {
                        Vehicle *u = RoadVehFindCloseTo(v, x, y, new_dir);
                        if (u != NULL) {
                                v->cur_speed = u->First()->cur_speed;
                                return false;
                        }
                }

                uint32 r = RoadVehEnterTile(v, tile, x, y);
                if (r == VETS_CANNOT_ENTER) {
                        assert(IsRoadStopTile(tile));
                        v->cur_speed = 0;
                        return false;
                }

                if (IsInsideMM(v->state, RVSB_IN_ROAD_STOP, RVSB_IN_DT_ROAD_STOP_END) && IsStationTile(v->tile)) {
                        if (IsReversingRoadTrackdir(dir) && IsInsideMM(v->state, RVSB_IN_ROAD_STOP, RVSB_IN_ROAD_STOP_END)) {
                                /* New direction is trying to turn vehicle around.
                                 * We can't turn at the exit of a road stop so wait.*/
                                v->cur_speed = 0;
                                return false;
                        }

                        /* If we are a drive through road stop and the next tile is of
                         * the same road stop and the next tile isn't this one (i.e. we
                         * are not reversing), then keep the reservation and state.
                         * This way we will not be shortly unregister from the road
                         * stop. It also makes it possible to load when on the edge of
                         * two road stops; otherwise you could get vehicles that should
                         * be loading but are not actually loading. */
                        if (IsDriveThroughStopTile(v->tile) &&
                                        RoadStop::IsDriveThroughRoadStopContinuation(v->tile, tile) &&
                                        v->tile != tile) {
                                /* So, keep 'our' state */
                                dir = (Trackdir)v->state;
                        } else if (IsRoadStop(v->tile)) {
                                /* We're not continuing our drive through road stop, so leave. */
                                RoadStop::GetByTile(v->tile, GetRoadStopType(v->tile))->Leave(v);
                        }
                }

                if (r != VETS_ENTERED_WORMHOLE) {
                        v->tile = tile;
                        v->state = (byte)dir;
                        v->frame = start_frame;
                }
                if (new_dir != v->direction) {
                        v->direction = new_dir;
                        if (_settings_game.vehicle.roadveh_acceleration_model == AM_ORIGINAL) v->cur_speed -= v->cur_speed >> 2;
                }
                v->x_pos = x;
                v->y_pos = y;
                VehicleUpdatePosition(v);
                RoadZPosAffectSpeed(v, v->UpdateInclination(true, true));
                return true;
        }

        if (rd.x == RDE_TURNED) {
                /* Vehicle has finished turning around, it will now head back onto the same tile */
                DiagDirection enterdir = (DiagDirection)(rd.y);
                Trackdir dir;

                if (v->roadtype == ROADTYPE_TRAM && IsNormalRoadTile(v->tile) && HasExactlyOneBit(GetRoadBits(v->tile, ROADTYPE_TRAM))) {
                        /*
                         * The tram is turning around with one tram 'roadbit'. This means that
                         * it is using the 'big' corner 'drive data'. When the tram reaches the
                         * 'turned' marker, we switch it to the corresponding straight drive data.
                         */
                        dir = DiagDirToDiagTrackdir(enterdir);
                } else {
                        if (v->IsFrontEngine()) {
                                /* If this is the front engine, look for the right path. */
                                dir = RoadFindPathToDest(v, v->tile, enterdir);

                                if (dir == INVALID_TRACKDIR) {
                                        v->cur_speed = 0;
                                        return false;
                                }
                        } else {
                                dir = FollowPreviousRoadVehicle(v, prev, v->tile, enterdir);
                        }
                }

                const RoadDriveEntry *rdp = _road_drive_data[_settings_game.vehicle.road_side][dir];

                int x = TileX(v->tile) * TILE_SIZE + rdp[RVC_AFTER_TURN_START_FRAME].x;
                int y = TileY(v->tile) * TILE_SIZE + rdp[RVC_AFTER_TURN_START_FRAME].y;

                Direction new_dir = RoadVehGetSlidingDirection(v, x, y);
                if (v->IsFrontEngine() && RoadVehFindCloseTo(v, x, y, new_dir) != NULL) return false;

                uint32 r = RoadVehEnterTile(v, v->tile, x, y);
                if (r == VETS_CANNOT_ENTER) {
                        v->cur_speed = 0;
                        return false;
                }

                v->state = dir;
                v->frame = RVC_AFTER_TURN_START_FRAME;

                if (new_dir != v->direction) {
                        v->direction = new_dir;
                        if (_settings_game.vehicle.roadveh_acceleration_model == AM_ORIGINAL) v->cur_speed -= v->cur_speed >> 2;
                }

                v->x_pos = x;
                v->y_pos = y;
                VehicleUpdatePosition(v);
                RoadZPosAffectSpeed(v, v->UpdateInclination(true, true));
                return true;
        }

        /* This vehicle is not in a wormhole and it hasn't entered a new tile. If
         * it's on a depot tile, check if it's time to activate the next vehicle in
         * the chain yet. */
        if (v->Next() != NULL && IsRoadDepotTile(v->tile)) {
                if (v->frame == v->gcache.cached_veh_length + RVC_DEPOT_START_FRAME) {
                        RoadVehLeaveDepot(v->Next(), false);
                }
        }

        /* Calculate new position for the vehicle */
        int x = (v->x_pos & ~15) + rd.x;
        int y = (v->y_pos & ~15) + rd.y;

        Direction new_dir = RoadVehGetSlidingDirection(v, x, y);

        if (v->IsFrontEngine() && !IsInsideMM(v->state, RVSB_IN_ROAD_STOP, RVSB_IN_ROAD_STOP_END)) {
                /* Vehicle is not in a road stop.
                 * Check for another vehicle to overtake */
                RoadVehicle *u = RoadVehFindCloseTo(v, x, y, new_dir);

                if (u != NULL) {
                        u = u->First();
                        /* There is a vehicle in front overtake it if possible */
                        if (v->overtaking == 0) RoadVehCheckOvertake(v, u);
                        if (v->overtaking == 0) v->cur_speed = u->cur_speed;

                        /* In case an RV is stopped in a road stop, why not try to load? */
                        if (v->cur_speed == 0 && IsInsideMM(v->state, RVSB_IN_DT_ROAD_STOP, RVSB_IN_DT_ROAD_STOP_END) &&
                                        v->current_order.ShouldStopAtStation(v, GetStationIndex(v->tile)) &&
                                        v->owner == GetTileOwner(v->tile) && !v->current_order.IsType(OT_LEAVESTATION) &&
                                        GetRoadStopType(v->tile) == (v->IsBus() ? ROADSTOP_BUS : ROADSTOP_TRUCK)) {
                                Station *st = Station::GetByTile(v->tile);
                                v->last_station_visited = st->index;
                                RoadVehArrivesAt(v, st);
                                v->BeginLoading();
                        }
                        return false;
                }
        }

        Direction old_dir = v->direction;
        if (new_dir != old_dir) {
                v->direction = new_dir;
                if (_settings_game.vehicle.roadveh_acceleration_model == AM_ORIGINAL) v->cur_speed -= v->cur_speed >> 2;
                if (HasBit(v->state, RVS_IN_ROAD_STOP) && _road_stop_stop_frame[_settings_game.vehicle.road_side][v->state & RVSB_TRACKDIR_MASK] == v->frame) {
                        /* The vehicle is in a road stop, and at its stopping
                         * frame. Make a delay here until the vehicle has
                         * turned around. */
                        v->UpdateInclination(false, true);
                        return true;
                }
        }

        /* If the vehicle is in a normal road stop and the frame equals the stop frame OR
         * if the vehicle is in a drive-through road stop and this is the destination station
         * and it's the correct type of stop (bus or truck) and the frame equals the stop frame...
         * (the station test and stop type test ensure that other vehicles, using the road stop as
         * a through route, do not stop) */
        if (v->IsFrontEngine() && ((HasBit(v->state, RVS_IN_ROAD_STOP) &&
                        _road_stop_stop_frame[_settings_game.vehicle.road_side][v->state & RVSB_TRACKDIR_MASK] == v->frame) ||
                        (HasBit(v->state, RVS_IN_DT_ROAD_STOP) &&
                        v->current_order.ShouldStopAtStation(v, GetStationIndex(v->tile)) &&
                        v->owner == GetTileOwner(v->tile) &&
                        GetRoadStopType(v->tile) == (v->IsBus() ? ROADSTOP_BUS : ROADSTOP_TRUCK) &&
                        v->frame == RVC_DRIVE_THROUGH_STOP_FRAME))) {

                RoadStop *rs = RoadStop::GetByTile(v->tile, GetRoadStopType(v->tile));
                Station *st = Station::GetByTile(v->tile);

                /* Vehicle is at the stop position (at a bay) in a road stop.
                 * Note, if vehicle is loading/unloading it has already been handled,
                 * so if we get here the vehicle has just arrived or is just ready to leave. */
                if (!HasBit(v->state, RVS_ENTERED_STOP)) {
                        /* Vehicle has arrived at a bay in a road stop */

                        if (IsDriveThroughStopTile(v->tile)) {
                                TileIndex next_tile = TILE_ADD(v->tile, TileOffsByDir(v->direction));

                                /* Check if next inline bay is free and has compatible road. */
                                if (RoadStop::IsDriveThroughRoadStopContinuation(v->tile, next_tile) && (GetRoadTypes(next_tile) & v->compatible_roadtypes) != 0) {
                                        v->frame++;
                                        v->x_pos = x;
                                        v->y_pos = y;
                                        VehicleUpdatePosition(v);
                                        RoadZPosAffectSpeed(v, v->UpdateInclination(true, false));
                                        return true;
                                }
                        }

                        rs->SetEntranceBusy(false);
                        SetBit(v->state, RVS_ENTERED_STOP);

                        v->last_station_visited = st->index;

                        if (IsDriveThroughStopTile(v->tile) || (v->current_order.IsType(OT_GOTO_STATION) && v->current_order.GetDestination() == st->index)) {
                                RoadVehArrivesAt(v, st);
                                v->BeginLoading();
                                return false;
                        }
                } else {
                        /* Vehicle is ready to leave a bay in a road stop */
                        if (rs->IsEntranceBusy()) {
                                /* Road stop entrance is busy, so wait as there is nowhere else to go */
                                v->cur_speed = 0;
                                return false;
                        }
                        if (v->current_order.IsType(OT_LEAVESTATION)) v->current_order.Free();
                }

                if (IsStandardRoadStopTile(v->tile)) rs->SetEntranceBusy(true);

                StartRoadVehSound(v);
                SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
        }

        /* Check tile position conditions - i.e. stop position in depot,
         * entry onto bridge or into tunnel */
        uint32 r = RoadVehEnterTile(v, v->tile, x, y);
        if (r == VETS_CANNOT_ENTER) {
                v->cur_speed = 0;
                return false;
        }

        if (v->current_order.IsType(OT_LEAVESTATION) && IsDriveThroughStopTile(v->tile)) {
                v->current_order.Free();
        }

        /* Move to next frame unless vehicle arrived at a stop position
         * in a depot or entered a tunnel/bridge */
        if (r != VETS_ENTERED_WORMHOLE) v->frame++;
        v->x_pos = x;
        v->y_pos = y;
        VehicleUpdatePosition(v);
        RoadZPosAffectSpeed(v, v->UpdateInclination(false, true));
        return true;
}

static bool RoadVehController(RoadVehicle *v)
{
        /* decrease counters */
        v->current_order_time++;
        if (v->reverse_ctr != 0) v->reverse_ctr--;

        /* handle crashed */
        if (v->vehstatus & VS_CRASHED || RoadVehCheckTrainCrash(v)) {
                return RoadVehIsCrashed(v);
        }

        /* road vehicle has broken down? */
        if (v->HandleBreakdown()) return true;
        if (v->vehstatus & VS_STOPPED) return true;

        ProcessOrders(v);
        v->HandleLoading();

        if (v->current_order.IsType(OT_LOADING)) return true;

        if (v->IsInDepot() && RoadVehLeaveDepot(v, true)) return true;

        v->ShowVisualEffect();

        /* Check how far the vehicle needs to proceed */
        int j = v->UpdateSpeed();

        int adv_spd = v->GetAdvanceDistance();
        bool blocked = false;
        while (j >= adv_spd) {
                j -= adv_spd;

                RoadVehicle *u = v;
                for (RoadVehicle *prev = NULL; u != NULL; prev = u, u = u->Next()) {
                        if (!IndividualRoadVehicleController(u, prev)) {
                                blocked = true;
                                break;
                        }
                }
                if (blocked) break;

                /* Determine distance to next map position */
                adv_spd = v->GetAdvanceDistance();

                /* Test for a collision, but only if another movement will occur. */
                if (j >= adv_spd && RoadVehCheckTrainCrash(v)) break;
        }

        v->SetLastSpeed();

        for (RoadVehicle *u = v; u != NULL; u = u->Next()) {
                if ((u->vehstatus & VS_HIDDEN) != 0) continue;

                u->UpdateViewport(false, false);
        }

        /* If movement is blocked, set 'progress' to its maximum, so the roadvehicle does
         * not accelerate again before it can actually move. I.e. make sure it tries to advance again
         * on next tick to discover whether it is still blocked. */
        if (v->progress == 0) v->progress = blocked ? adv_spd - 1 : j;

        return true;
}

Money RoadVehicle::GetRunningCost() const
{
        const Engine *e = this->GetEngine();
        if (e->u.road.running_cost_class == INVALID_PRICE) return 0;

        uint cost_factor = GetVehicleProperty(this, PROP_ROADVEH_RUNNING_COST_FACTOR, e->u.road.running_cost);
        if (cost_factor == 0) return 0;

        return GetPrice(e->u.road.running_cost_class, cost_factor, e->GetGRF());
}

bool RoadVehicle::Tick()
{
        this->tick_counter++;

        if (this->IsFrontEngine()) {
                if (!(this->vehstatus & VS_STOPPED)) this->running_ticks++;
                return RoadVehController(this);
        }

        return true;
}

static void CheckIfRoadVehNeedsService(RoadVehicle *v)
{
        /* If we already got a slot at a stop, use that FIRST, and go to a depot later */
        if (Company::Get(v->owner)->settings.vehicle.servint_roadveh == 0 || !v->NeedsAutomaticServicing()) return;
        if (v->IsChainInDepot()) {
                VehicleServiceInDepot(v);
                return;
        }

        /* Only go to the depot if it is not too far out of our way. */
        TileIndex rfdd = FindClosestRoadDepot(v, true);
        if (rfdd == INVALID_TILE) {
                if (v->current_order.IsType(OT_GOTO_DEPOT)) {
                        /* If we were already heading for a depot but it has
                         * suddenly moved farther away, we continue our normal
                         * schedule? */
                        v->current_order.MakeDummy();
                        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                }
                return;
        }

        DepotID depot = GetDepotIndex(rfdd);

        if (v->current_order.IsType(OT_GOTO_DEPOT) &&
                        v->current_order.GetNonStopType() & ONSF_NO_STOP_AT_INTERMEDIATE_STATIONS &&
                        !Chance16(1, 20)) {
                return;
        }

        SetBit(v->gv_flags, GVF_SUPPRESS_IMPLICIT_ORDERS);
        v->current_order.MakeGoToDepot(depot, ODTFB_SERVICE);
        v->dest_tile = rfdd;
        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
}

void RoadVehicle::OnNewDay()
{
        AgeVehicle(this);

        if (!this->IsFrontEngine()) return;

        if ((++this->day_counter & 7) == 0) DecreaseVehicleValue(this);
        if (this->blocked_ctr == 0) CheckVehicleBreakdown(this);

        CheckIfRoadVehNeedsService(this);

        CheckOrders(this);

        if (this->running_ticks == 0) return;

        CommandCost cost(EXPENSES_ROADVEH_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR * DAY_TICKS));

        this->profit_this_year -= cost.GetCost();
        this->running_ticks = 0;

        SubtractMoneyFromCompanyFract(this->owner, cost);

        SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
        SetWindowClassesDirty(WC_ROADVEH_LIST);
}

RoadPathPos RoadVehicle::GetPos() const
{
        if (this->vehstatus & VS_CRASHED) return RoadPathPos();

        Trackdir td;

        if (this->IsInDepot()) {
                /* We'll assume the road vehicle is facing outwards */
                td = DiagDirToDiagTrackdir(GetGroundDepotDirection(this->tile));
        } else if (IsStandardRoadStopTile(this->tile)) {
                /* We'll assume the road vehicle is facing outwards */
                td = DiagDirToDiagTrackdir(GetRoadStopDir(this->tile)); // Road vehicle in a station
        } else if (this->state > RVSB_TRACKDIR_MASK) {
                /* Drive through road stops / wormholes (tunnels) */
                td = DiagDirToDiagTrackdir(DirToDiagDir(this->direction));
        } else {
                /* If vehicle's state is a valid track direction (vehicle is not turning around) return it,
                 * otherwise transform it into a valid track direction */
                td = (Trackdir)((IsReversingRoadTrackdir((Trackdir)this->state)) ? (this->state - 6) : this->state);
        }

        return RoadPathPos(this->tile, td);
}