[parkingrift]

>Wait, so you're saying that people would crash into you if you drove the speed limit?

Maybe not literally crash into you, but that is certainly possible. People will swerve around you, ride your bumper, flash their high beams at you, honk, pull in front of you and hit the brakes, and other dangerous road rage type behavior. It is absolutely unsafe to drive the speed limit.

In general the safest thing to do is just to keep up with traffic.

[caf]

People will swerve around you, ride your bumper, flash their high beams at you, honk, pull in front of you and hit the brakes, and other dangerous road rage type behavior.

I don't think the one being unsafe in this scenario is the one driving the speed limit!

[fastball]

Does it matter if the result of the behavior is that you are unsafe?

[Xylakant]

That’s exactly what the driver in front of you and behind you use as justification for being above the limit: I had to go with the flow of traffic. A self-perpetuating force that forces everyone to be too fast.

[parkingrift]

Disagree. Traffic engineers study roadways and recommend speed limits based on safety and human behavior. And then cities and states ignore them and use speed limits to generate revenue.

>A self-perpetuating force that forces everyone to be too fast.

If it were actually too fast, most people wouldn't travel that speed. Have you ever noticed that traffic speed ebbs and flows with the road conditions or time of day? People will drive the speed they feel safe driving, and for most drivers it's (typically) much faster than the posted speed limit. And if the conditions are poor, it's much slower.

[acdha]

> Traffic engineers study roadways and recommend speed limits based on safety and human behavior.

This isn't really true: what usually happens is that they either go with a default or they do a study and set the limits at the 85th percentile. For a separated highway, that works fairly well but it often has bad results for mixed spaces: the people commuting through a neighborhood, for example, are trying to go as fast as possible but the people who live there are more concerned about safety, the impacts of those decisions on how they use their space (I grew up hearing that “nobody walks in California” which really meant “nobody wants to walk 3 miles further to use the few signaled crosswalks”), etc. A big problem here are the outliers: most of the risk comes from the top of the speed distribution — even if half of the drivers scrupulously follow the speed limit, the speeders are the ones who will influence people's safety perception of the road.

[throwaway0a5e]

> And then cities and states ignore them and use speed limits to generate revenue.

I think for highways and other limited access roads they're often concerned with minimizing complaints much like the commentary we're seeing up and down these comments so they slap a small number on the sign knowing full well that traffic will ignore it and call it job well done.