The shooting down sucks, I can improve it.
function SpitfireSpeedCheck(%this, %obj)
{
	if(!isObject(%obj))
		return;
	%vehicle = %obj;
%slot = 0; //Play the sound in the driver's spot
	%speed = vectorLen(%obj.getVelocity());
	if(%speed < 0) //Keeps throwing random negative numbers when train is at dead stop
	    %speed = 0;
	if(%speed < 10)
	    %vehicle.playAudio(%slot, SpitfireidleSound);
	else if(%speed < 30)
	    %vehicle.playAudio(%slot, Spitfirethrottle1Sound);
	    
	schedule(500,0,"SpitfireSpeedCheck",%this,%obj);
}
//Keeps throwing random negative numbers when train is at dead stop
Oh, nice, feel free to credit me.