no matter what i try, the car stalls out. ive tried 3x1 steep slopes, 3x2 slopes, dash panel steps between slopes, etc. the vehicle stops as soon as it reaches the end of the slope. i've also tried having the car drop onto the next road, accelerating into the slope, not accelerating. no idea whats going on. we're trying to build a high way and the exit ramps simply do not work.