Hacker News Reader

Comment by crote | Hacker News Reader

> People who are likely to have crashes are likely to be able who ignore the limit.

... which is why you have to do actual road design. You can't just put up a speed sign and hope people will magically abide by it. Roads need to be designed for the speed you want people to drive. When done properly the vast majority of drivers will follow the speed limit without ever having to look at the signs, because it'll be the speed they will feel comfortable driving.

View on HN

> You can't just put up a speed sign and hope people will magically abide by it.

Off topic, but one of the more maddening things I see here in the US is signs which say "End thus-and-such speed limit." I don't want to know what the speed limit was. I want to know what it is!

In Ontario a new speed zone is always signed with "BEGINS" below it, which is very helpful if you missed the last sign. I wish this was standard practice across Canada.

In much of Europe, including the UK, they have the concept of standardised "national" speed limits, which vary depending on the road type and which you are expected to know. When a road returns to the national speed limit, the sign is a white circle with a slash through it, indicating that there are no more local speed limits and the national speed limit is in effect.

There are at most three standard speed limits on Europe: built up areas, highways and motorways.

I find this easier to remember than the constantly changing limits in the USA. In my two weeks here, I've seen every multiple of 5 between 5 and 70mph.

In Sweden at least, there's an informal rule that a new speed zone is marked with speed limit signs on both sides of the road, whereas a continued limit is marked with a sign only on the driving side of the road.

I never quite saw the point though -- my response is the same either way: adhere to the limit that applies going forward. (I suppose maybe it's useful feedback of inattention and the need for rest?)

Proper design of road networks also makes traffic flow better. Many congested areas would actually benefit from removing some roads altogether.

I believe you're referring to Braess' Paradox, right? This was a very surprising effect for me to learn about, just recently Veritasium covered it in their video on a mechanism that becomes "shorter when you pull on it": https://www.youtube.com/watch?v=-QTkPfq7w1A

[0] https://en.wikipedia.org/wiki/Braess%27_paradox

Yes, I saw the same video! Having played Cities: Skylines, it was not that much of a surprise, more of a neat formal explanation.

It isn't road design, it is behavioural/cultural. People will drive recklessly when they do not care, for whatever reason, about the people they may injure by doing so. That is it. If you look at comparisons between countries, it is clear that means are different.

There are people who don't care at all, but most people will drive around the speed that the road encourages. That includes things like how straight the road is, what kinds of interactions, the presence of sidewalks, trees, and many other clues.

Neighborhoods can be designed to send signals about the appropriate speed, without signs or rumble strips or speed bumps. Some people will ignore these, just as they'll ignore signs, but most drivers will do what they expect for that kind of road.

I disagree, idiots are everywhere.

The thing is, the vast majority of people - regardless of culture - have some basic sense of self-preservation. Speeding is easy when that 30km/h road is designed like a 120km/h highway. Speeding is a lot harder when that 30km/h road has speed bumps, chicanes, bottlenecks, and is paved with bricks rather than asphalt: if you try to speed, it'll quickly feel like you need to be a professional rally driver to keep your car under control.

Deliberately making roads "unsafe" forces people to slow down, which in turn actually makes it safe.

That's true. I stopped riding the bus because the road to the stop had big speed bumps put in, and it turns out distracted drivers fly off the road when they hit them, and one near miss was enough to make me drive instead (sure it's a cognitive bias, but it's enough to make me pick the more convenient option). One fewer pedestrian means one fewer potential pedestrian death!

…plus the potential pedestrian deaths you cause by collision plus the actual impact of the extra pollution

Reply on news.ycombinator.com