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Comment by kfarr | Hacker News Reader

This is great and there’s another area of influence that I’ve heard other traffic engineers discuss: platoon pacing. A platoon is the word that traffic engineers give to a group of cars traveling together. A platoon is most explicitly visible on a corridor with signals timed for a green wave, but occurs in many other contexts.

Human drivers often race when in a platoon— not even on purpose it’s just an instinct to go as fast or faster than other cars which has a feedback effect to increase platoon speed.

Waymos, following the exact speed limit, don’t do this. On 1 lane streets they literally set the platoon pace to the legal speed limit.

The effect of this is hard to study and quantify but it’s a real and positive impact of self driving cars on city streets. Haven’t seen research on this topic yet.

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This also came up recently in a thread about speed governors: https://news.ycombinator.com/item?id=43812856 Just a few governor-equipped vehicles (e.g. from public fleets or prior speeding offenders) can reduce speeding on the whole road.

On most roads, speeding isn’t a safety issue and shouldn’t be discouraged, as road throughput is important. Speed limits are usually set too low due to standardized inflexible policies or desire for revenue.

On some roads, however, it is a massive safety issue, and everyone is driving unsafely because the road is designed badly for its intended purpose. (So-called “stroads” are the canonical example.)

It’s an issue for everyone not in a car

Yeah and we should definitely leave deciding the appropriate speed to the drivers. Because, uh, throughput is important, got it. Is safety important? Who knows, but throughput definitely is!

That is what happens now. Most drivers do not cause accidents from speed most of the time. This is a red herring.

Speed is always a contributing cause to a collision. It's pretty simple to understand, if colliding parties are going slower, they would have more time to prevent collision.

If you are going slower you can make up for missing details, missing a brake signal, missing a pedestrian.

Speed is the underlying reason accidents happen. No one is creeping at 2 MPH and just running into things, they have time to stop.

This doesn't even take into consideration that speed results in significantly larger impact (and thus damage to passengers, environment, and vehicles)

I would expect "most roads" to be comprised of residential roads, and I find it hard to believe speeding on those roads is not a safety issue.

The speed limits on most residential roads are too low from a variety of factors, including tradition, policies, and desire for revenue or to generate PC to pull over drivers.

You don't drive 25 on residential roads, because you know this to be true. Neither do I, nor does anyone else.

Patently untrue. I do, sometimes slower. My kids’ friends live on these roads.

Yeah, well, I don't/can't drive, so maybe my perspective as a pedestrian is just different :)

Do you have any sources to backup your claims that that's too fast and is more unsafe than speeding?

The above comment is getting downvoted, and I suspect it's due to a misunderstanding of their intent. Yes, high speeds can make collisions (especially, as another commenter points out, to pedestrians and cyclists) more dangerous. However, just as human drivers subconsciously speed up when part of a group of cars, they are not often conscious of the environmental queues informing the speed at which they drive. Given the poster's allusion to 'stroads', I suspect that they're in favor of traffic engineering patterns that encourage speed reduction based on safe context queues without solely relying on an unenforced and often unobeyed traffic speed.

Consider this video on Dutch traffic calming: https://www.youtube.com/watch?v=bAxRYrpbnuA.

Lane narrowing, raised walkways, curves in the road (chicanes), etc. are all environmental queues that enforce safe traffic speed based on context, without relying on conscious human compliance.

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