Distributed embedded control systems play an increasing role in modern automotive designs and there is a pressing need to investigate the impact of different design decisions on system safety and reliability. A highly effective method of performing the testing for such an investigation is via a suitably detailed "hardware-in-the-loop" (HIL) simulation. This paper describes a novel HIL testbed that has been developed for this purpose in the Embedded Systems Laboratory at the University of Leicester. An overview of the simulator is provided, followed by detailed descriptions of the vehicle and driver models that are employed. The performance of the system is illustrated using an example based on an adaptive cruise control system.