Collision avoidance system (presafe plus) failed to warn (as advertised by mbusa) of an imminent rear end collision on an expressway. The system is supposed to provide an audible warning signal based on the rate of change of the closing distance between mb and a vehicle in front. Moreover, if the driver ignores the warning signal, the mb is supposed to apply brakes automatically. Neither of these two events took place, resulting in a rear end collision. The highway before and at the point of collision was straight with no curves. After collision damage repair by an mb dealership and assurance from the dealer that the safety systems were operational, I tested the vehicle multiple times by driving the mb into a variety of large boxes the fronts of which were covered with metallic foil. All tests failed to provide both an audible warning as well as automatic braking (see www.youtube.com/watch?V=6_D9A_axav4 for one example of test). Mbusa advertising in 2015 touted these safety features on tv and youtube videos. What was missing from these infomercials is information on the reliability of these "safety" systems (I.e., what is the probability that the system will function as advertised). I suspect that this probability is quite low, and if so, this fact should have been provided to the consumer. Also, if my experience with the actual accident and my additional testing is any indication of reliability, merc3des Benz vehicles incorporating presafe plus should be subjected to a NHTSA recall.

- Philadelphia, PA, USA