Unlike other precollision and lane mitigation systems, which typically use a series of radar or laser sensors to detect vehicles in front of them, the GMC system uses a digital camera mounted on the windshield in front of the rearview mirror. The digital camera, combined with object- and range-detecting software, determines if an accident is pre-eminent. If it is, the system illuminates a warning icon and beeps to warn the driver. The system also will pre-charge the brakes, like other systems, if an accident is unavoidable. GM doesn’t mention if the system will pre-emptively tighten seat belts, adjust seating position, raise head restraints or close the windows as similar systems do. GMC’s precollision system only works at speeds above 25 mph.The digital camera also can detect lane markings and will warn if you’ve left your lane without signaling first. The system also can warn you if you’re following the vehicle in front of you too closely when driving at speeds above 25 mph.
GM’s system does have its limitations, which are caused by using a single digital camera and no other sensory inputs. If the camera is obstructed by snow or mud, its effectiveness will be limited, according to the automaker. We’re looking into whether rains is an issue for this system, too.
Update: Heavy rain and snow will affect the system, said GM's Ray Kiefer, who was quick to point out that the majority of accidents happen in clear weather conditions.
The system is a $295 option on the 2012 GMC Terrain, which is already on sale.