Autopilot Showdown: Tesla P85D vs Mercedes E63S Wagon

Posted by: Bernard Winkelmann onOctober 20th, 2015

Dealing with the unknown

When the Mercedes doesn’t know where it is, it simply disengages steer assist and you, as the driver, must take over. This usually happens when the car in front of you turns abruptly (like a right hand turn) or when the lane markings disappear at higher speeds. It also happens when the road turns more than about 10 degrees or when the lane you are in ends. The Mercedes requires that your hands be on the wheel to take over in these types of situations. You can take them off and it will drive autonomously for about 15 seconds before reminding you to hold the wheel again. You can “trick” the system into thinking you are holding the wheel by simply putting your knee against it.


The Tesla, on the other hand, dealt with ambiguity much better. Driver intervention was rarely requested as the car seemed to know what to do when the traffic pattern wasn’t obvious. I think that using the GPS and maps aids immensely as it knows where it is and how to behave. The GPS must help when it is following the car in front as the indecision in the system lasts far shorter time than in the Mercedes. It knows how to handle uncertainty much better and faster.


What is truly amazing is how these cars can drive themselves given that each municipality marks the roads in different ways. Both cars got stumped by poor lane definition, but the Mercedes was the only one of the two to give up.

When confronted with a merge lane that was ending, the Tesla stays in the lane it is in to the bitter end. It will, however, move over after it has gone over the solid white line on the right. This was one of the few areas where things got sketchy and taking over is the right course of action most of the time. The Mercedes simply gives up and reverts control to the driver. The Mercedes systems was easily confused by the filled expansions cracks in the road. It would disengage steer assist frequently due to the lack of defined lines. If you do not pay attention to the little green steering wheel on the dash, the car will begin to veer off the road as there are no audible warnings that the system has disengaged.


One of the scarier issues we encountered with the Mercedes was the lack of smoothness. If you set the speed to 70 km/h while behind a car, it will maintain distance perfectly. If that car turns off on an exit, the car gets confused as it doesn’t know whether to follow the car or the lines. If the car in front slows to 30 km/h and turns off, Distronic will see that the obstacle is gone and will accelerate hard to 70km/h. This makes the car a 630+ hp 5000 lb missile that is accelerating hard on its own with no steering as it hasn’t acquired the lane markings yet. We had two full on panic stops because the car was approaching stopped cars at an intersection too fast for my liking. The other issue is the transition in modes from following the car to following the road markings isn’t fully baked. The car has trouble transitioning between the two and requires the driver to intervene as the transition is taking place. This means you have to keep your eye on the info screen to see if the Steer assist is active (green wheel) or not. This is probably why Mercedes insists on you having your hands on the wheel at all times.

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