[mostapha]

That's interesting, because Mercedes's Traction Control system almost killed me one night. Apparently it's possible to accidentally induce a very slight but controllable oversteer slide by overshooting the exit to a fast curve and touching a rumble strip with the outside tires. No surprise there.

In a normal car, you keep your front wheels on the line you want to follow, release power, then smoothly add power to "shift weight" to the rear wheels and increase traction (acceleration causes the rear suspension to compress, making the rear tires push harder on the ground, increasing the normal force and increasing rear wheel traction). Doing that stops the oversteer (rear wheel skid).

In a Mercedes, the car assumes that you're an idiot for doing that, cuts engine power to the drive (rear) wheels, and applies breaks to the OUTSIDE REAR WHEEL. That procedure has the effect of decompressing the rear suspension and decreasing traction to the rear wheels, which are already skidding. The slide that resulted was unrecoverable. Yank the parking break and shift into neutral while in a hard corner at 40mph if you want to know what it felt like. For a few seconds, my instincts and the car's Traction Control fought each other as I tried to correct for the skids that improperly braking the rear wheels was causing.

Finally, I came to rest having skid across the double yellow…and then somehow the automatic transmission stalled.

It was a "mistake" that could have been fixed in less than a second driving a 1908 Model T. After a hundred years of innovations, Mercedes has completely removed the driver from direct control of the vehicle, WITHOUT an option to turn off those so-called "features."

I spent the next several months talking to people who did tuning for Daimler-Chrysler for a shop in Montana, cracking ECU encryption to reprogram the fuel injectors and intake system to perform well at high altitudes. And apparently there's no good way to turn off that Traction Control system except removing large chunks of code from the ECU, which voids the warranty and might have serious side effects. When I learned more about how the Traction Control system actually works, I sold the car.

I will never own another Mercedes. They breed laziness and irresponsibility without giving competent drivers the control they need to drive safely.

I'm currently an avid BMW fan because of two major factors: first, it's possible to buy manual transmissions without special ordering a new car from Germany; second, it is possible–by holding a button on the console for a few seconds–to COMPLETELY disable traction control. I have driven in snow and ice, torrential downpours, and heavy traffic in the last year. I haven't driven with Traction Control on since Mercedes almost killed me in 2006.

Frankly, I think EVERY SINGLE ONE of the safety features you suggested is a horrible idea. Pay attention to what you're doing, and don't drive if you're not physically and mentally capable of driving. I don't want my car to wake me up if I fall asleep driving…I want to be smart enough to not drive that night.

Frankly, the more I hear about Mercedes safety features, the more distance I like to keep between me and them on the highway.

[encoderer]

I'm sure you feel very strongly that you're correct and that the systems were incorrect. And that's fine. But the fact that you disable the TCS in your BMW indicates that it's the technology you dislike and not the Mercedes implementation.

I'm happy for you that you've found a car you like. For me, I don't feel BMW has the same track record of safety innovation, but even before I grew to value that, what disuaded me most from owning a BMW is the fact that they use runflats only. And even if you've got a salesman willing to swap them out with conventional tires, there is no place in the trunk for a spare without it just sitting in there rolling around, taking up space. But I respect that BMW makes some fine cars and they feel very different on the road than does a Mercedes.

The criticisms you have about making drivers "lazy" is the same thing some people said about antilock brakes. And in fact, I have an uncle who swears as you do that if he had full control over the brakes, he'd have avoided an accident.

For me, knowing that these safety systems -- able to react in fractions of a second -- are there to help save my life and keep safe the woman I love, is invaluable. And I believe that for every one of your stories, there's dozens or hundreds of stories where these things led to a person walking away from an accident than they may not otherwise have survived.

I think the average person would agree. A system that beeps if you fall asleep at the wheel? Yes. A system that nudges your steering wheel fi you drift over the centerline? Yes. None of these things even augment your driving, they just direct yoru attention to the road.

In fact, the only thing I mentioned that does intervene in your driving is the blind spot intervention.

Anyhow, glad you didn't have any serious issues. And I hope we both know how fortunate we are to be able to sit here and debate the relative merits of one German sports sedan vs another.

[enjalot]

I think you should keep in mind that you appear to be an intelligent, skilled and avid driver. For you driving is an experience you take seriously and also seem to enjoy. I'm not worried about what you do on the road, but I am worried about the millions of less intelligent and skilled drivers that are pushing 3000lbs of metal around at lethal speeds.

I think you are justified in wanting and buying a machine that suits your needs, but please don't assume that everyone is or even should be as adamant about driving as you are. I for one will happily let the computer take the wheel and allow me to focus on things I care about like conversation or coding. If I want a joy ride hopefully I'll be successful enough to own a classic gasoline powered driving machine ;)

[mostapha]

Driving at a high level is one thing. It requires a lot of skill and concentration.

Not killing people is completely different: it requires basic skills and some small measure of multi-taking ability. Which is more important, reacting to the car changing lanes without a signal in front of you or finishing your sentence RIGHT NOW?

The problem isn't even skill level. Driving normally at city and highway speeds is easy. The vast majority of 1st world residents know how to do it, and very very few of them make mistakes severe enough to affect anyone else's lives. The average driver is nowhere near as bad at it as most people seem to think.

But taking the driver's commitment to and awareness of the risks inherent in driving away and placing that burden on active "safety features" is a bad thing. I know their hearts are in the right place and that I'm not the person these systems are designed for. But they're going to get people killed.

My issue with Mercedes's Traction Control in particular isn't even that it makes drivers lazy. It's that in at least that situation, it can't tell the difference between power-induced oversteer and breaking-induced oversteer. In that situation, it reacted EXACTLY WRONG. It doesn't matter whether the driver is competent or not if the system makes the opposite changes that it should.

[DrewG]

It's not the average drivers that need help, its the bad drivers. The ones who roll through a red light turning right, but look left the entire time, which is a very common way for pedestrians to get hit by cars. The system in the article would probably prevent tons of those accidents. I'm all for taking control away from bad drivers, even if that means we also have to take control away from the average and good drivers.

[mostapha]

And if they're running through a red light, that means the cross street has a green.

The pedestrian might be in slightly less danger if the car reacts properly. But then the car stops unexpectedly and the driver wonders what happens…and winds up stopped in an intersection for some nonzero amount of time.

Also, unless I'm visualizing this wrong (right turn on red hits a pedestrian in the crosswalk to his right that's parallel to his original direction of travel) the only way the pedestrian would have been in that crosswalk at all is if s/he was crossing against the light and crossing the path of cars going straight on a green.

[DrewG]

The ped is travelling perpendicular to the original direction of the car (crossing from right to left from the cars point of view) and is most likely just stepping off the sidewalk.

[bradleyland]

I'm not sure I'll be able to change your mind about this, but I'd like to express my opinion on your sentiment and leave it at that.

I think that maybe you're wrong about a few things here. First and foremost, that your slide was recoverable.

I'm a car guy myself. Like you, I insist on manual transmissions with rear wheel drive. I've been to driving schools, read extensively about how suspension affects handling dynamics, and turned a few wrenches in my time. Even with all that, I try to remain humble about my own driving abilities and the fact that while I enjoy it, I don't drive professionally, so I shouldn't expect professional results.

Your comments about skid recovery apply to the input controls that are available to you as the driver. They don't apply to the input controls available to the traction control systems in your car. For every subtle detail that you learned about handling using the steering wheel, brake, and clutch, there are equivalents for the systems available to the traction control system, such as individual wheel braking.

Stopping a slide is about controlling rotation. You cannot use the brake to directly rotate the vehicle because you only get one brake pedal. The best use of that brake pedal, as a driver, is in controlling the speed and weight distribution of the automobile. That is the most you can hope for.

"My issue with Mercedes's Traction Control in particular isn't even that it makes drivers lazy. It's that in at least that situation, it can't tell the difference between power-induced oversteer and breaking-induced oversteer. In that situation, it reacted EXACTLY WRONG. It doesn't matter whether the driver is competent or not if the system makes the opposite changes that it should."

The stability program in a Mercedes absolutely knows the difference between power-induced oversteer and braking-induced oversteer. It uses accelerometers, yaw sensors, throttle position sensors, and individual wheel speed sensors to infer your intended direction of travel. Braking the outside rear wheel does transfer weight forward, but it has a far more significant positive effect on correcting rotation because of the asymmetrical application of braking force. Your slide was simply unrecoverable. You think that it was recoverable, but you'll never know for sure. Based on the physics involved, I think you're wrong.

I've tested the limits of these systems myself. My 2006 GTI had ESP. I took it out to a dirt road and explored the limits under slalom conditions and hard turns. These systems are amazing at recovering slides that can be recovered. If I pushed hard enough, I could "break through" to an uncontrollable slide, however. When you "overshoot" your mark, brake, turn, then hit a rumble strip (which significantly reduces available traction) you end up in an unrecoverable slide.

The irony here is that your Mercedes' ESP system didn't almost kill you, you did.

[encoderer]

Thanks for offering your opinion. While I want to respect the GP's personal experience, your comments echo my feelings. My favorite part of a Mercedes (and this is surely true for other premier makes) is that everything seems to have been thought out and engineered ^1. And with my own personal experience of the cars TCS, I felt it very hard to believe that the Mercedes TCS would be so simplistic.

^1 Not to say I don't have my issues with the cars -- stuff like a crappy Chinese made iPod interface.

Edit: That video is stunning. Thanks for the share.

[bradleyland]

I'd strongly encourage you to take advantage of any driving school that Mercedes offers. I've read countless messages from individuals who insist that these safety systems (ABS, TCS, and ESP) are a detriment to their ability to drive the car, but I've experienced them in two makes of automobile (VW and BWM) now, and I now know from first-hand experience that they work fantastic. There is no replacement for testing them out for yourself.

[bradleyland]

To support my point, here is a video of Tiff Needell testing an older version of ESP in a Jaguar on a sheet of ice. The ability of the system to stop a car from sliding out of control under these conditions is just mind boggling.

This 6:21 start point shows both (with/without) tests:

http://www.youtube.com/watch?v=j-hHWSQhKuc&feature=fvwre...

[DrewG]

I'm afraid this is whats going to prevent adoption of more automatic cars. The people who care about cars don't want the features, but its the people who don't care about cars that would benefit most. And they don't pay attention.

[mostapha]

Once again, they won't benefit if the systems aren't a hell of a lot better than Mercedes was capable of producing in 2006.

And unless you know what's going on "under the hood" well enough to either evaluate their code or design a real-world test that you can perform in an empty parking lot…you're left to decide based on what Mercedes says. And they're never going to say "our system can't detect the cause of a skid…it just reacts based on detecting the speed wheels are spinning and assumes the driver is completely incompetent."

Some of the systems are great. There's no reason a car sold today shouldn't have ABS: the driving techniques required to get similar performance out of non-ABS brakes are very skill specific and time-intensive to develop. It's not worth it for >99% of drivers. And there are "good" traction control systems. Subaru's computer-controlled differentials in their AWD system are pretty good. But that system isn't capable of making a mistake as bad as the "active braking" systems that are coming out.

[DrewG]

So you are in favor of technology that takes control away from drivers as long as it works? Perhaps we are actually on the same page here...

[gfodor]

You may not want the car to wake you up, but you'll certainly want the car of the incompetent driver next to you to wake him up before he careens into you on the highway.

[mostapha]

No, I don't. I'd rather he have to take responsibility for his actions and decide whether he really needs to take that chance instead of thinking "it's okay that I'm exhausted…my car will wake me up."

[gfodor]

Most of the time, in my own experience, when I am close to falling asleep while driving, I would have never been able to realize how tired I was before leaving on the trip. Even if you feel wide awake before you leave your destination, a late night drive on the highway can induce sleep, with the hum of the highway and the flying by of the lines on the road.

You're basically suggesting that people decide to not get in their cars if they even slightly think they might be too tired to drive. You know as well as I do that there's no way to measure this (unlike drinking, where if you consumed any alcohol in the last several hours you shouldn't get behind the wheel.) So, it's a bit of a pipe dream to think drivers are actually in the position to make a judgement call about their own risk of falling asleep at the wheel before leaving.

Regardless, my point was that these safety systems are meant to protect responsible drivers from irresponsible ones. I'm skeptical that the presence of safety systems could somehow convert a responsible driver to an irresponsible one.

[mostapha]

You don't make the decision to drive and then that's it. At any point, you can decide "i'm too tired," and pull off.

Take a nap in your car. Let someone else drive if you're not alone. Call a cab and pick up your car in the morning. Call Safe Ride, and they'll send a driver and a moped that will fit in your trunk if you're somewhere they operate.

There are always alternatives to putting yourself in a dangerous situation. And, I believe these systems will lead people to drift further into these types of dangerous situations before even thinking about safer alternatives.