The end goal of a remote attack against a vehicle is physical control, usually by injecting CAN messages onto the vehicle's network. However, there are often many limitations on what actions the vehicle can be forced to perform when injecting CAN messages. While an attacker may be able to easily change the speedometer while the car is driving, she may not be able to disable the brakes or turn the steering wheel unless the car she is driving meets certain prerequisites, such as traveling below a certain speed. In this talk, we discuss how physical, safety critical systems react to injected CAN messages and how these systems are often resilient to this type of manipulation. We will outline new methods of CAN message injection which can bypass many of these restrictions and demonstrate the results on the braking, steering, and acceleration systems of an automobile. We end by suggesting ways these systems could be made even more robust in future vehicles.