Like so many of today's technologies, drive-by-wire is primarily a response to tightening emission standards. As with fuel injection and integrated engine controllers, drive-by-wire systems improve engine efficiency while cutting vehicle emissions. They do this by replacing clunky and inaccurate mechanical systems with highly advanced and precise electronic sensors. Currently, drive-by-wire applications are being used to replace the throttle-cable system on newly developed cars like the models already mentioned.
These systems work by replacing conventional throttle-control systems. Instead of relying on a mechanical cable that winds from the back of the accelerator pedal, through the vehicle firewall, and onto the throttle body, drive-by-wire consists of a sophisticated pedal-position sensor that closely tracks the position of the accelerator and sends this information to the Engine Control Module (ECM). This is superior to a cable-operated throttle system for the following reasons:
By eliminating the mechanical elements and transmitting a vehicle's throttle position electronically, drive-by-wire greatly reduces the number of moving parts in the throttle system. This means greater accuracy, reduced weight, and, theoretically, no service requirements (like oiling and adjusting the throttle cable).
The greater accuracy not only improves the driving experience (increased responsiveness and consistent pedal feel regardless of outside temperature or pedal position), but it allows the throttle position to be tied closely into ECM information like fuel pressure, engine temperature and exhaust gas re-circulation. This means improved fuel economy and power delivery as well as lower exhaust emissions.
With the pedal inputs reduced to a series of electronic signals, it becomes a simple matter to integrate a vehicle's throttle with non-engine specific items like ABS, gear selection and traction control. This increases the effectiveness of these systems while further reducing the amount of moving parts, service requirements and vehicle weight.
and yes I nicked this somewhere