ASR will prevent the DRIVE wheels from losing traction/spinning. ESP prevents over/understeer by braking ANY wheel(s). Both systems evolved from the familiar ABS system. When ASR came along, it included the previously known ABS functions. When ESP was introduced, it included both ABS and ASR functions as well as the stability program. Even though you'll see warning indicators for ABS, ASR, ESP, and BAS, there is only one control module running everything, although for a short time the BAS system had a separate ECU. BAS(Brake assist system)is an enhancement of the ABS function. Sensotronic brake control(SBC)was introduced on the 2003 SL and is said to be the worlds' first brake-by-wire system. It shares many components with the traction system and is yet another way MB enhances existing technology to come up with new applications. I wonder what's next?