protected:

	/**

	 * Update the speed of the vehicle.

	 *

	 * It updates the cur_speed and subspeed variables depending on the state

	 * of the vehicle; in this case the current acceleration, minimum and

	 * maximum speeds of the vehicle. It returns the distance that that the

	 * vehicle can drive this tick. #Vehicle::GetAdvanceDistance() determines

	 * the distance to drive before moving a step on the map.

	 * @param accel     The acceleration we would like to give this vehicle.

	 * @param min_speed The minimum speed here, in vehicle specific units.

	 * @param max_speed The maximum speed here, in vehicle specific units.

	 * @return Distance to drive.

	 */

	FORCEINLINE uint DoUpdateSpeed(uint accel, int min_speed, int max_speed)

	{

		uint spd = this->subspeed + accel;

		this->subspeed = (byte)spd;

		/* When we are going faster than the maximum speed, reduce the speed

		 * somewhat gradually. But never lower than the maximum speed. */

		int tempmax = max_speed;

		if (this->cur_speed > max_speed) {

			tempmax = max(this->cur_speed - (this->cur_speed / 10) - 1, max_speed);

		}

		this->cur_speed = spd = Clamp(this->cur_speed + ((int)spd >> 8), min_speed, tempmax);

		int scaled_spd = this->GetAdvanceSpeed(spd);

		scaled_spd += this->progress;

		this->progress = 0; // set later in *Handler or *Controller

		return scaled_spd;

	}