I've used a few adaptive cruise controls that will not maintain a great enough following distance to come to a complete stop in the following distance (eg, in the case that the car in front of you swerves out of the lane revealing an obstacle).

Did that around here and you’ll have people swerving around you.

The problem I have with adaptive cruise: if you set your gap too wide, usually the suggested gap, people keep swerving into it, so it makes for a very nauseating drive if you are somewhere with not enough traffic that you are moving slowly, but too much traffic that people don't have to change lanes.

Just yesterday I was driving in the left lane with cruise control set to the maximum allowed velocity, with the maximum gap behind a car driving in front of me. Of course someone overtook me on the right (illegal in Germany) just to swerve in front of me and then drive at the same speed, just 20m further ahead. He ended up being first at the red lights. I’ll never understand it…

Regardless if you’re going the limit or not, it’s illegal to cruise on the leftmost lane when you ‘re not overtaking.

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

If you are traveling 80 in the left lane while the right lane is locked in at 60 (trucks who are limited to power speed limits), it is simply impossible to travel in the right lane. You are constantly overtaking vehicles, so it works out legally, but, yes, if someone wants to go 90, there is a conflict. Ideally, you wouldn’t cruise in the left lane because there would be room to cruise in the right lane, but higher traffic situations don’t really allow for it (well, not so high that you can’t go 80 in the left lane).

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

If there was room for someone to overtake on the right I don't think your scenario applies.

Well, it sort of does. Imagine your doing 100 in the left lane, as does the car in front of you and the three cars in front of them. There’s a truck doing 80 in the middle lane some 500m away. All of you are going to pass it. Now a sixth car starts tailgating behind the last in line and because there’s left a big safety gap he’s overtaking on the right.

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…

You shouldn't overtake on the right.

Exactly. It’s illegal here in Germany. I don’t know if it’s ok somewhere else.

It's not, and it's a bit worrying that it's not widespread knowledge.

This is often true, but it varies from state to state.

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

I know that. But what am I supposed to do when the left lane leads to the exit I want to go to?

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

People don’t intuitively notice speed, they see following distance as a proxy for speed: people with longer following distances are perceived as “driving slow” and they feel they are going faster if they tailgate. Both untrue, but almost universally assumed without a second thought

Wow. I’ve been driving for 20+ years and never realized this is how some people think.

This is not a problem, just chill out.

I have to imagine the level of discomfort depends on the car. I've never ridden in a vehicle with adaptive cruise control, but if it responds quickly to someone jumping in line, that could go beyond annoying to motion sickness if it keeps happening.

Having owned a car with this feature, it's very uncomfortable when it suddenly and unexpectedly brakes hard to allow a car in.

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

Ah. I see. My 2015 Model S doesn't do that, it just gently increases the spacing until it is as it was.

Sounds like we need adaptive horn control for when people do that.

In America? Get ready for more road rage shootings

I'm sorry, but can't you just set it to medium or close distance if you're having problems with people jumping into your gap?

Ya you can do that, but then it feels like dangerous. When it gets like that I usually just shut it off and control distance myself (and "cough" adjust it to dissuade swerving and then back off for safety).

ah. my car doesn't have adaptive cruise control but I've rented cars that do. it took a bit to get used to medium and feel comfortable and not dangerous, but then people aren't cutting in.

From some motorcycling book I remember the right response to that is to slow down even more and maintain following distance with the new car in front of you. If we let ego go and can be home 2-5 minutes late on average all will be well.

I've found that the adaptive cruise has made me an almost "egoless driver". It does keep a conservative distance, and aggressive drivers do fill in the gap, but I don't care as much when I'm not the one on the pedal.

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).

I live in a cramped east coast city. If everyone around here followed the DMV guidelines for distance between cars, morning rush hour would probably be from 4am to 11am. Sure, the fact that everyone's driving in such a tiny little space is the problem, but the infrastructure here doesn't leave us much choice.

That's questionable. Flow should improve from increased spacing; it might even offset the density decrease.

Even if the length of the cars end-to-end is often greater than the length of craggy narrow street between tightly packed but unevenly placed intersections with anywhere from 3 to 8 entry points? Even when all of the 5 highways people are trying to enter and exit– all within the same mile– are all completely backed up? I'd have to see that to believe it.

Those seems like situations where extra spacing will help accomodated unexpeded mergings and lane changes without slowing traffic down.

The majority of the roads that aren't highways do not have lanes. The road layout is largely from a hundred or two years before cars existed.

I fail to see the relevance of this comment?

>>> Those seems like situations where extra spacing will help accomodated unexpeded mergings and lane changes without slowing traffic down.

>> 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?

So the point you were trying to make is that single land roads don't face traffic issues from merges and lane changes? That seems to trivially be false in my experience. Having driving all over the USA on roads with a single lane in each direction, merges and lane changes are by far the biggest cause of traffic slow downs.

Sure thing, bud.

Do you suppose average speeds would be higher or lower without the frequent accidents due to failure to brake in time?

The traffic is not frequently caused by accidents. It's a small city so it's pretty clear when that happens. We have some of the lowest accident stats in the country. It's probably because any time there are a significant number of cars on the road, the entire region slows to a crawl.

I'm pretty much out of the habit of using cruise control even with newer adaptive cruise control because it really encourages maintaining a constant speed even on roads that are really too busy to allow it.

In this city, even at 3:30 in the morning on Sunday, cruise control is just useless. It's a spaghetti pile of twisty roads and a billion intersections. Even on the major thoroughfares, you're not going to drive more than 20 seconds without hitting a intersection. To make matters worse, it's all way too disorganized to efficiently coordinate-- almost nothing is perpendicular-- so when traffic is light they just have very short light cycles and you're nearly guaranteed to hit a red light in a few blocks, max. Most residential streets are only wide enough to accommodate one car, but in many cases there's no logistical way to make them one way, so you just have to get good at constantly negotiating who should yield and who should go with oncoming traffic. That, specifically, causes shockingly few problems! But it makes for complex traffic patterns that require a lot of cognitive load to handle. If there was good public transit here, it would be great.

The situation is similar in the Chicago area. Some roads are almost perpetually bogged down. If there is an accident or stalled car, it gets worse. I see two things that affect flow.

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.

Yeah I've had my fair share of big city traffic, but this is very different. In many ways driving here is a lot easier than driving in a place like downtown Chicago or Manhattan because it's much much much lower-volume, so there's a lot less action you have to pay attention to, but all of the roads are tiny and twisty. It's like heart circulation vs pinkie tip circulation. And since it's so small, even being slowed down to a crawl from one end of the city to the other as part of a longer drive would affect your drive less than even moderately bad traffic in a metropolis.

I often try to follow the car-length-per-10mph rule. It's often times not possible. Cars with just duck in front of you and people behind you will pass you. One of many reasons why I hate daily driving.