I apologize for any flame wars this creates, since people find driving to be deeply personal and any findings which may criticize their driving habits is generally frowned upon.

The main reason I almost always have adaptive cruise control on is so that it keeps me at a safe braking distance from cars in front of me but I've found that most people do not care.

Just yesterday there was a corolla that was following a school bus so closely i'm sure it could sniff the bus' ass. That driver was one hard brake away from being decapitated by the school bus bumper.

They were rightly annoyed. It’s also a hefty fine if you’re caught doing this.

This usually happens when you are approaching a city and are going to get a new lane or two pretty soon anyways.

I was the last in line, going at the exact same speed as the cars in front of me, just leaving enough space. Why would I switch lanes?

Plus it was leading to an exit anyway…

https://www.mit.edu/~jfc/right.html

Also: there was someone in front of me going the same speed, I just left a big gap

And it can be very confusing to the vehicle behind you.

With the full map and destination time in front me, I don't feel the urge to game the system (or maybe I'm just getting old).

>> The majority of the roads that aren't highways do not have lanes.

> I fail to see the relevance of this comment?

... you don't see how roads lacking lanes applies to the efficiency of merges and lane changes?

1. As traffic builds and distance between cars decreases, the flow becomes susceptible to "shock waves". (Just search Youtube for "traffic shockwave" for an example. I think it happens when someone taps their brakes and the next car behind them has to brake a little harder ans so on down the line until traffic comes to a complete stop.

2. As a commuter and occasional weekend driver I recognized two traffic patterns. During normal commutes, the same drivers drive the same routes every day and most settle into a pattern of maintaining speed, remaining in lane, moving to merge and so on in harmony with other drivers. There is the occasional outlier, driving slower than everyone else or weaving in and out and trying to get ahead by weaving and passing in whatever lane momentarily has space. On weekends I see drivers who are unaccustomed to the driving situation and simply don't mesh well with other traffic. Even though there is generally less traffic, it does not flow as well. There is more lane changing and stuff like crossing three lanes to get to an exit because they forgot where they needed to exit.

Excess traffic is a problem and unfortunately we seem to be able to overfill the available capacity any time it is increased.

When I worked in downtown Chicago I was very happy to be able to take commuter rail to work rather than to have to drive, but those options seem to be more the exception than a regular option. That's a different discussion.

Stopped car in unexpected place.

1 car in front of your vehicle, between you and the stopped car.

Assuming the car in front of you switches lanes around the stopped car with 1 car length of space between it and the stopped car.

So 2 car lengths + your personal gap for you to slow down.

So you could be going no faster than 20mph worst case (0 personal gap).

The issue is that the car in front of you doesn't need to stop, so can potentially "suck you in" at an unsafe speed, before you realize you'll need to come to a complete stop (assuming your lane change is blocked).

I think it is the only time though that I've been faced with a stationary car suddenly appearing where I wouldn't expect one, and that's very different to the car in front needing to slam on the brakes with whom you can share some stopping distance.

fwiw 6 seconds at 45mph is 120 meters. That we can comfortably go that far in 6 seconds is a modern marvel, but it's also 20 car lengths.

I'm almost hesitant to believe that any car on the market has good enough sensors to do 6 seconds. That is a very long distance at highway speeds.

Quote: "For example, if you drive at 56 mph (90 km/h), the distance is maintained as follows: Distance 4 - approximately 172 feet"

172 feet at 56 mph is 2.1 seconds.

Not saying that you are wrong (maybe a recent model has better cruise control), but I think most people vastly overestimate the adaptive cruise controls in their cars and ~4 seconds would, for reference, vastly outperform 2023 Tesla Y in that aspect.

I always drive setting four and it keeps a very comfortable amount of distance. I think something is incorrect here because I definitely get at _least_ three seconds, or maybe I'm counting too fast.

Thanks for looking into this & being friendly!

40mph is 58 feet per second, so that’s less than a second to

Your “rule of thumb” is AT BEST highly misleading.

Typical humans take about 250ms to react, and that’s before you actually do anything. There’s 15ft (at least) gone before you even touch the pedal.

I appreciate your attitude here. Mine is opposite. Dangerous driving injures, maims, and murders both perpetrators and innocents alike. Criticise bad driving loudly and often. You might save lives. I had to tell my mother in law that her daughter, my wife, lost her life in a road traffic accident. There are few aspects to serious road traffic accidents that are not horrific, and speaking up may save lives. Every year, 1.19 million people die as a result of a road traffic accident. Between 20 to 50 million people suffer non-lethal injuries, many of those leading to disability.[1]

[1] https://www.who.int/news-room/fact-sheets/detail/road-traffi...

People speeding through the 30 mph limit in my village boils my blood like nothing else and I’m one of those parents who shouts at traffic on the school run, even driven by people I know. This has likely cost me a few invitations to the pub but I don’t care.

"Road Traffic Collision" is encoded in the applicable laws.

If you open enough space ahead of you for a car, someone will cut in. Driving too closely isn't something only you can do something about.

In fact, because of the aforementioned behaviour, it's safer to drive too close because it's far more dangerous for a car to cut in in front of you because he perceives "enough" space to do so.

This is not correct, stopping distance scales as the square of speed. The distance you'd need to stay from the vehicle in front to be able to stop if it magically came to an instantaneous stop is far, far larger than anyone will reasonably keep.

The stopping distance at 65mph, including reaction time, is at least 300ft. That's ~20 car lengths, not 6.5 that your formula would yield. If conditions are wet, your tires are not in great shape, or you're not paying attention, it's going to be much longer.

The solution is typically to swerve with the other car, but sometimes that’s not possible.

It should be impossible to accelerate. None but maybe the most high-output engines should have enough power to overcome the car’s brakes. Aerodynamic drag is not quite a rounding error, but I don’t imagine it counts for a whole lot in this scenario in comparison.

But they said it's FSD who's following too closely.

I'd expect automated system should react even better, because it pays attention constantly. That's the whole point, especially when it's called "Full".

It's not even a question of "taking back control". You're expected to be in control of the vehicle.

For example, most cars prevent fiddling too much with its entertainment system while driving, even though drivers are expected to not do that while driving.

To me, it seems like this is where a computer should be a million times better. It might take me or you a half second to figure out whats happening, but software should be able to immediately detect that a car is stopped in front of you.

This shouldnt be a problem at all with a LiDAR based system, but I can see how a camera system might have trouble with it (possibly indicating that LiDAR should still be used for at least the near future)