standard input does not store those values, it is possible that you can disable standard input and use an alternative input system.
steering angle(assuming front axle can steer) : vehicle.getNormalizedSteering() * vehicle.getAxis(0).getMaxSteerAngle()
throttle : vehicle.getEngine().getThrottle()
brakes(for front left wheel here) : vehicle.getAxle(0).getLeftWheel().getBraking()