During rush hour traffic on Highway 101 Southbound near Redwood City, I experienced an incident while utilizing AutoPilot and AutoSteer. Despite being in stop-and-go traffic, the vehicle did not respond to the car in front which suddenly came to a complete stop. Neither the Automatic Emergency Braking system nor warning sounds, which has been known to activate erroneously, were triggered. As a result, I was forced to manually brake at the last moment, but there was not enough time for manual intervention and the vehicle collided with the car in front. It is worth noting that every other instance in which I have utilized AutoPilot and AutoSteer, which occurs on nearly every trip I take, the vehicle has been able to respond and brake, albeit with slow reaction times and close distances.