2015 Buick Regal Owner Manual - Page 228

Driving and Operating ACC may operate differently in a sharp curve. It may reduce the vehicle speed if the curve is too sharp. Other Vehicle Lane Changes 9-47 ACC may detect a vehicle that is not in your lane and apply the brakes. When following a vehicle and entering a curve, ACC may not detect the vehicle ahead and accelerate to the set speed. When this happens, the vehicle ahead symbol will not appear. ACC may occasionally provide an alert and/or braking that is considered unnecessary. It could respond to vehicles in different lanes, signs, guardrails, and other stationary objects when entering or exiting a curve. This is normal operation. The vehicle does not need service. ACC will not detect a vehicle ahead until it is completely in the lane. The brakes may need to be manually applied.