Tesla please fix this - Autopilot

[Alphacar]

Enjoying driving the car every day. Tesla is making lot of great improvements including to the autopilot but not sure why is still doing this, my other car RAV4 does a much better job at this. I'm on the highway cruising at 55 miles. Half mile far from me, there is a sudden traffic and all the cars are stopped or going slower. The car seems to speed toward them and instead of decelerating and slowly going to a stop by maintaining the distance set on the cruise control, it put a break really hard near the other cars (Kind of freaky) . No matter what you will say, I really do not see any logic in it, the car is well able to see the distance between one car and the other, including speed and etc, that is why is the best so far with auto pilot and self driving. There must be some reason beyond it that I can not understand. By the way the cruise control should always obey the distance limit that you set but it changes based on the speed and etc. It should be always at the same distance no matter what, Am I missing something?

 

[Enginerd]

It might just be a matter of expectation. I agree with you that it frequently brakes later and harder than necessary. I worked to increase my tolerance a little. I wait and let the car brake when it needs to, and it almost always slows down before it would become a safety issue. Over time, I think the car is looking and planning further ahead as well. I think we're meeting in the middle ground. In wet or icy conditions, I would probably feel differently.

 

[LoudMusic]

I agree with both of your observations It's good, and it could do better.

 

[Twiglett]

I used to dial down the set speed so it would slow down sooner which used to work quite well with old AP.
However beta 10.4 pretty much ignores the set speed and slows down extremely slowly, it seems to take >1/2 mile to slow from 70-55.
Only "fix" I have now is to disengage AP and reset when we are in the line with the cars in front

 

[JHCCAZ]

...By the way the cruise control should always obey the distance limit that you set but it changes based on the speed and etc. It should be always at the same distance no matter what, Am I missing something?

I do agree with your prior point about braking earlier and more smoothly when approaching stopped traffic. However I do not agree at all that the following distance should be a fixed distance independent of the speed.

This is a pretty fundamental point regarding safe following distance. You should follow cars in front at a more or less adequate time interval, because this takes into account
a) human reaction time, a good fraction of a second, and
b) increased braking distance as you are moving at a higher speed.

(And by the way this doesn't really change just because you are driving a computerized car with faster reaction time and good brakes. You still have human-driven cars and trucks behind you that should not be expected to react or stop faster than normal just because your car can do so.)

This is exactly why driving instructors teach a following rule based on time interval: classically this was taught as the "two second rule", i.e. you should be able to count two seconds from the time the car in front passes a marker, to the time that you pass it.

The physics would say that a completely fixed time interval is not really correct but it's easy to understand and to teach. In actuality most drivers do not obey this two-second rule; I think more typically people follow at about 1 second, give or take. This is definitely not as safe but it's not completely crazy if you are attentive.

Recently I've seen that official driving instruction courses are trying to teach a three or even three and a half second rule. While this may seem "safer" from a pure physics point of view, I think it's actually wrong to teach that. If you actually try to obey that extreme rule in moderate-to-heavy traffic, people will become very impatient with you and it actually becomes more dangerous because they will drive around you to fill that long gap.

But the bottom line is that a fixed distance is definitely not the right driving policy. Neither for human drivers, nor for computer drivers in mostly human-piloted traffic.