You Should Never Swerve. Good Advice?

Factual Questions
61

I like the “Don’t Veer For Deer” link. But what it advises is slow down, watch for deer, and brake, steer and stop if you are about to hit one. I think they’re more worried about people who try to treat it as a video game and avoid the deer while maintaining their lap time.

I remember a study on cars with ABS. One problem is they tended to get rear-ended by drivers without ABS. Really.

I’ve been thinking about this and today, when a kid actually ran out in front of my car, I made a bunch of observations.

I stood on my brakes. The car stopped in a couple of feet.

There wasn’t anywhere to swerve to.

There wasn’t any time to think.

And I was only going 20 mph in the first place because this was a residential area, the sort of area that looked like it had kids dashing out in front of cars.

Basically, I think your first instinct ought to be to brake, while you’re still assessing the situation. Then maybe steer around, maybe continue to brake, maybe a combination of both.

62

This is actually why I don’t like ABS. Sure, they improve stopping distance when you slam on the brakes, but if you build a car designed to stop best when the brakes are slammed, you create a generation of drivers who are trained to slam the brakes (or at least to have a false confidence in their vehicle’s ability to abruptly come to a stop). I believe that threshold braking is a more effective way of stopping. I’ve always stopped this way, but never had a term for it until now.

ABS testing compares the stopping distances of only one style of stopping (that of panicking and standing on the brake pedal). Drivers who are likely to panic and stomp the brakes are the same drivers who are likely to panic and release the brake when the pedal starts thumping and vibrating. I would love to see a study comparing threshold braking to ABS (has this been done?). After all, isn’t ABS just an automatic pulsating brake, creating a series of mini-skids at alternating wheels which are strategically time and placed? It seems that braking just enough so you aren’t quite to the point of going into a skid would still be a better way to stop.

I’ll also mention the idea that driver’s licenses are too easy to obtain. Panicky drivers should probably just take the bus.

63

No it isn’t. I’m starting class now so I don’t have time to explain, but I will be back later to explain.

agreed.

64

OK, I’m back. You have some common misconceptions about ABS in your post. Let’s go through how ABS works and why a good ABS system really is superior to your mark 1 mod 1 leg.
To explain how ABS works we have to consider a tire rolling down the road. The speed of the car is irrelevant. The car is coasting and driving straight ahead on a flat road. The relative speed between the tread and the road surface is 0 mph. If you are having trouble with this concept roll a pen across a table top until you understand.
OK, when you step on the brakes the wheel and tire slow down. the tire starts to slip just a bit on the pavement. This is a good thing as this slip is what brings the car to a stop. if you press harder the slip increases and the braking force increases. This continues until you hit about 12-13% slip, then the brake force drops off. When you get about 15% slip you are in a skid and directional control of the tires is lost.
What ABS does is that it monitors wheel slip and it only steps in if the slip starts to exceed 12-13%. ABS will then modify the brake pressure on the slipping wheel to keep the slip below 13% A good ABS system will do this on each wheel individually (4 channel system), a not quite so good system will do this to each front wheel individually, and the rears together (3 channel system). A very good system can modify the brake pressure at the wheel about 10-15 times per second. A pro race driver using threshold braking can do this about 5 or 6 times per second.
The next point where ABS is superior is the fact that SBS is always ready. Emergencies are just that, emergencies. They are not planned events. When you are out on the track, it is easy to plan and threshold brake. However when you are driving to the market talking to your SO and a kid darts out between parked cars, it is very easy to go past the threshold and into a skid. Sure you can let off, but extra stopping distance is eaten up while you are adjusting. Also can you be sure that you are right on the limit of adhesion for your tires and road surface? How do you know this? How do you know that you couldn’t brake just a little harder? With ABS I do not have to worry about this, the computer is constantly watching the acceleration and deceleration of the wheels to see if everything is OK. If I have to make a panic stop, I know that the ABS system will give me the maximum deceleration that is available.
OK, depending on just how strong your I’m a great driver gene is you might want to argue with the points above. Here is one where you cannot argue that you can out brake an ABS system. Your left and right wheels have different road surface conditions. For example your right wheels are on asphalt, and the left wheels are on concrete, or if you are driving where there is drainage down the center of the road and your left side wheels are running in water. Or there is some sand in the gutter on the right as you approach a turn. Without ABS your braking is limited to the wheel(s) with the least traction. You cannot brake different wheels with different force. My ABS system can modify each of the four wheels independently.
OK, and your argument about people getting scared when the ABS system kicks in and not being able to brake. Do you really think that these induhviduals can threshold brake successfully? You have a higher opinion of them than I do. They are the ones that will lock them up and slide into something.
On some model cars I can monitor the deceleration of the car in real time. With ABS the car will stop at the limit of adhesion of the tires, about .8G. With the ABS disabled I have never seen anyone go above about .57G without losing it, and going into a skid.

65

That is why I say they should not have gotten licenses to begin with. But I do think threshold braking can be learned and still should learned, no matter how good the technology is.

While I agree with what you said, I do believe that ABS has also contributed to a false sense of security (which is not a flaw of the technology of implementation, but yet another driver flaw). Improved stopping distance creates more confidence, more confidence leads to “Hey, I can follow closer because I have ABS,” thereby countering all the benefits. The same could be said of the I’m a great driver gene, however.

As a classic car owner, I must say that I really enjoy driving a heavy car with terrible brakes because it’s a constant reminder of just how horrifying it is to be screaming down the highway with your life pivoting on the smallest of mistakes. 70mph is supposed to be scary. Owning such a car makes me follow another second behind other drivers just because I know how scary it is in the whipping wind on the highway. Of course, following safely means I’m getting cut off by other drivers all the time, which is also dangerous! Knowing my brakes are terrible can make me more aware and alert. So there’s the “I’m gonna die!” factor to be considered, but that’s a psychology argument, not a physics one. ABS may be great technology (and still works with threshold brakers), but maybe auto manufacturers just need to go back to rattling sheetmetal, vibrating engine mounts, and uncomfortable seats to keep drivers aware that they are always a few feet from a gory death on the highways.

So, in summary, bad brakes make me more fearful of the danger, the fear makes a more conscientious driver, so I follow from a greater distance, which causes other drivers to cut me off, which creates more fear, which makes me even more fearful of the danger. I always look at it as I’m driving for the other drivers, because they aren’t capable of creating their own safety buffers. Expect the other guy to cut you off, and your only surprise while driving will be the day that he doesn’t.

I’ll add to this discussion that some driver’s education courses are teaching “car lengths” as measures of safe following distances. Arrgh! Following distance needs to be measured in time, not physical space. This makes all the difference in stopping distance, creating enough time to swerve if you need to, and even assess the situation to determine if you should swerve.