Important Note: This function has no effect on un-occupied vehicles and does not effect trains.

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
if(IsPlayerInAnyVehicle(playerid))
{
    if(isUtas(playerid))
    {
          if (newkeys & KEY_UP)
   {
              SetVehicleVelocity(GetPlayerVehicleID(playerid),1.0,0.0,0.0);
           }
             if (newkeys & KEY_DOWN)
           {
               SetVehicleVelocity(GetPlayerVehicleID(playerid),-1.0,0.0,0.0);
   }
   if (newkeys & KEY_LEFT)
   {
                SetVehicleVelocity(GetPlayerVehicleID(playerid),0.0,-1.0,0.0);
   }
   if (newkeys & KEY_RIGHT)
   {
                SetVehicleVelocity(GetPlayerVehicleID(playerid),0.0,1.0,0.0);
   }
}
}
return 1;
}
stock isUtas(playerid) {
    return (GetPlayerState(playerid) == PLAYER_STATE_PASSENGER) ? true : false;
}

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
if(IsPlayerInAnyVehicle(playerid))
{
    if(isUtas(playerid))
    {
          if (newkeys & KEY_UP)
   {
              SetVehicleVelocity(GetPlayerVehicleID(playerid),1.0,0.0,0.0);
           }
             if (newkeys & KEY_DOWN)
           {
               SetVehicleVelocity(GetPlayerVehicleID(playerid),-1.0,0.0,0.0);
   }
   if (newkeys & KEY_LEFT)
   {
                SetVehicleZAngle(GetPlayerVehicleID(playerid), -1);
   }
   if (newkeys & KEY_RIGHT)
   {
                SetVehicleZAngle(GetPlayerVehicleID(playerid), 1);
   }
}
}
return 1;
}
stock isUtas(playerid) {
    return (GetPlayerState(playerid) == PLAYER_STATE_PASSENGER) ? true : false;
}