It seems I might have wasted some of my time writing my last post in this thread.
Code:

---

		/*
		Notes:
			arrow keys left/right to steer
			up arrow key to move forward
			down arrow key to move backward slower than moving forward
			shift + up/down arrow key to move forward/backward faster
		*/
		//reset the torque values to 0
		//torque values will be 0 if no key is pressed
		//the car 'coasts' if no key is pressed
		my.carEngineTorque = 0;
		my.carSteerTorque = 0;
		//...
		if (key_cul) { 
			my.carSteerTorque = 1.0;
		}
		if (key_cur) {
			my.carSteerTorque = -1.0;
		}
		if (key_cuu) {
			my.carEngineTorque = my.car_maxToque;
		} /* else {
			my.carEngineTorque = -60.0;		// NO! You don't need to do this.
		} */
		if (key_cud) {
			my.carEngineTorque = -my.car_maxToque * 0.5;  //only half-speed in reverse
		}
		if (key_shift) {  
			//'turbo' will be applied in reverse or forward, but not otherwise
			my.carEngineTorque = my.carEngineTorque * 5;
		}
		//...
		wait(1);

---

Newton might be considered an 'intermediate topic' for users that might have reached an 'intermediate' skill level.
If you are going to use Newton, you might try to study the 'example' scripts included with Newton thoroughly.