The modern vehicle differs from its counterparts of just a decade ago by the all-pervasive presence of electronic control systems. Today the electronic control unit doesn't just set the spark timing or moderate some braking functions; it controls the throttle, the balance and setup of the suspension, the transmission and the differential. In addition, electronics co-ordinate all the interactions between these components. The majority of these devices can now be classed as safety-related, and their failure modes are accounted for using techniques such as HAZOP and FMEA. However it is not the norm to consider the effects of miscalibration; the working assumption is that calibration engineers "know what they are doing". In the real world where "chipping" is the fashion this assumption may no longer be valid.