4 ms·

I mean, speed is the obvious issue with road safety. It increases stopping distance by a large amount, at 50km/h (~30mph) you're not even stopping while you alr

by danhor 5y ago

I mean, speed is the obvious issue with road safety. It increases stopping distance by a large amount, at 50km/h (~30mph) you're not even stopping while you already at a standstill at 30km/h (~20mph). If everyone drove at 10km/h almost no fatal accident would happen (probably mostly old people reversing into others). According to german data, reducing the speed limit from 50km/h (~30mph) to 30km/h (~20mph) reduces heavy injuries and deaths by 60-70% (https://www.vsf.de/fileadmin/inhalte/public/06_Engagement/tempo30/Maria_Limbourg_Tempo30.pdf https://www.vsf.de/fileadmin/inhalte/public/06_Engagement/te...) and decreases fatalities after a collision with a pedestrian from 80% to 30%. That's not quite mad max, but still very bad. We know that even for interstates speed limits have an large effect (https://www.sciencedirect.com/science/article/pii/S000145759900010X https://www.sciencedirect.com/science/article/pii/S000145759...), with deaths rising by ~15% after the speed limit was increased from 55mph (afaict, for urban interstates it was mostly raised by 10mph, with average travel speed only changing slightly). So even at those speeds there is a very noticable effect on deaths. If these numbers apply to speed limits, it's obvious that they should also apply to speeding. Even more so, it makes it clear that setting the speed limit higher has an pretty large effect on safety, so people do use the speed limit as a guide (with, as you said, often some amount of additional speed), so raising the speed limit seems like a very bad idea. All the figures I've seen for US speed limits seem in line with most of the speed limits commonly used in Germany, which are more on the high side for the EU. I don't know how you come to the conclusion that they're amazingly low.

chrismcb 5y ago
Yes, the faster you drive the more likely an accident will occur and the more deadly it might be... That is a separate issue than "speeding"
- danhor 5y ago
  Why? The issue with speeding is that ... you're driving faster. And as I've laid (at least somewhat) the speed limits the US commonly employs are sane as a choice and also very common in other countries. A huge issue is that american residential roads are way overbuilt, further encouraging speeding. A lot of residential roads in Central Europe have specific provisions encouraging and forcing drivers to slow down. The residential streets in America sometimes look like a small, two-lane, highway regarding their width and straightnes.
zionic 5y ago
The problem with most of this data is that it is preposterous on its face. Really, 30mph car impacts with pedestrians had an 80% fatality rate? What about 45, 75, and 150 MPH? Should we analyze those as well, or should we realize how silly this all is? The solution has always been to physically isolate pedestrian traffic from vehicles at anything above trivial speeds. 30-45mph car traffic on a flat plane with joggers and moms pushing strollers is stupid. These aren’t hard problems to solve, we’d just rather spend $15 Billion on our 14th aircraft carrier instead of pedestrian bridges/walkways/tunnels/elevated roadways etc. No one is suggesting obvious interface points like airport drop off/pickup lanes allow 75mph traffic. The point is that for the VAST majority of roads in the US pedestrian traffic is nonexistent and speed limits are 20-30% too low. So low even the cops don’t really enforce them (unless you’re black or the officer has a quota to meet). We have huge stretches of flat, controlled access, well maintained super highways stuck at 1950’s speed limits (65MPH). Yet when we talk about fixing this all we hear about is how someone killed a bus full of nuns doing 70 in a 25mph school zone. Otherwise rational people seem entirely incapable of nuance when it comes to the speed discussion.
- danhor 5y ago
  > Or should we realize how silly this all is? Why? It's an important question to have data on. It's essential to designing neighborhoods > The solution has always been to physically isolate pedestrian traffic from vehicles at anything above trivial speeds How in residential roads? By installing overpasses everywhere (they suck for pedestrian traffic and accessibility), installing traffic lights everywhere (they're already way to common in America and really suck for traffic flow) or do the same thing other countries have done, which is to slow drivers down (by design & by law) in residential roads. The first two options are also pretty expensive, can take a lot of land and many counties already suffer financially from their road infrastructure. In general, roads with speed limits above 30mph are not common inside urban environments in germany (with quite a few exceptions, especially for large arteries, which are often being put underground or getting their speeds reduced). Installing sidewalks more commonly in the US would already be great, but this data is from germany, where a street without a sidewalk is an uncommon (although not totally rare) occurrence. Having >30mph traffic inside urban areas is mostly stupid. It increases land use, costs, discourages anything other than car use and is really dangerous. There should be at most only a handful of roads with higher speeds in cities with >500.000 people. > US pedestrian traffic is nonexistent There are somewhat obvious reasons for that, among them hostile road design & high speeds. It's close to suicide to try to walk anywhere in many places in the US. > So low even the cops don’t really enforce them I don't know if you've looked at other countries, but enforcing speed limits, especially in such a way to act as an effective deterrent, isn't commonly done (with exceptions like switzerland). Regarding the highways: That's the reason I've searched for data in the US regarding the change of the speed limit from 55mph to ~65mph, which has a very significant (but not as large as in residential roads) effect. I can't imagine further increasing it not having a similar effect. That also shows that the speed limit does have a somewhat large effect on travel speed (at least in the top end), because otherwise there wouldn't be that many issues. I'd also be interested in changes for the average travel speed in the US, because it doesn't increase as much as you'd think in the >100km/h in many european places, even without significant amounts of speeding, due to cars scaling really badly at density with higher speeds.

by danhor 5y ago

chrismcb 5y ago

Yes, the faster you drive the more likely an accident will occur and the more deadly it might be... That is a separate issue than "speeding"

danhor 5y ago
Why? The issue with speeding is that ... you're driving faster. And as I've laid (at least somewhat) the speed limits the US commonly employs are sane as a choice and also very common in other countries. A huge issue is that american residential roads are way overbuilt, further encouraging speeding. A lot of residential roads in Central Europe have specific provisions encouraging and forcing drivers to slow down. The residential streets in America sometimes look like a small, two-lane, highway regarding their width and straightnes.

zionic 5y ago

The problem with most of this data is that it is preposterous on its face. Really, 30mph car impacts with pedestrians had an 80% fatality rate? What about 45, 75, and 150 MPH? Should we analyze those as well, or should we realize how silly this all is? The solution has always been to physically isolate pedestrian traffic from vehicles at anything above trivial speeds. 30-45mph car traffic on a flat plane with joggers and moms pushing strollers is stupid. These aren’t hard problems to solve, we’d just rather spend $15 Billion on our 14th aircraft carrier instead of pedestrian bridges/walkways/tunnels/elevated roadways etc. No one is suggesting obvious interface points like airport drop off/pickup lanes allow 75mph traffic. The point is that for the VAST majority of roads in the US pedestrian traffic is nonexistent and speed limits are 20-30% too low. So low even the cops don’t really enforce them (unless you’re black or the officer has a quota to meet). We have huge stretches of flat, controlled access, well maintained super highways stuck at 1950’s speed limits (65MPH). Yet when we talk about fixing this all we hear about is how someone killed a bus full of nuns doing 70 in a 25mph school zone. Otherwise rational people seem entirely incapable of nuance when it comes to the speed discussion.

danhor 5y ago
> Or should we realize how silly this all is? Why? It's an important question to have data on. It's essential to designing neighborhoods > The solution has always been to physically isolate pedestrian traffic from vehicles at anything above trivial speeds How in residential roads? By installing overpasses everywhere (they suck for pedestrian traffic and accessibility), installing traffic lights everywhere (they're already way to common in America and really suck for traffic flow) or do the same thing other countries have done, which is to slow drivers down (by design & by law) in residential roads. The first two options are also pretty expensive, can take a lot of land and many counties already suffer financially from their road infrastructure. In general, roads with speed limits above 30mph are not common inside urban environments in germany (with quite a few exceptions, especially for large arteries, which are often being put underground or getting their speeds reduced). Installing sidewalks more commonly in the US would already be great, but this data is from germany, where a street without a sidewalk is an uncommon (although not totally rare) occurrence. Having >30mph traffic inside urban areas is mostly stupid. It increases land use, costs, discourages anything other than car use and is really dangerous. There should be at most only a handful of roads with higher speeds in cities with >500.000 people. > US pedestrian traffic is nonexistent There are somewhat obvious reasons for that, among them hostile road design & high speeds. It's close to suicide to try to walk anywhere in many places in the US. > So low even the cops don’t really enforce them I don't know if you've looked at other countries, but enforcing speed limits, especially in such a way to act as an effective deterrent, isn't commonly done (with exceptions like switzerland). Regarding the highways: That's the reason I've searched for data in the US regarding the change of the speed limit from 55mph to ~65mph, which has a very significant (but not as large as in residential roads) effect. I can't imagine further increasing it not having a similar effect. That also shows that the speed limit does have a somewhat large effect on travel speed (at least in the top end), because otherwise there wouldn't be that many issues. I'd also be interested in changes for the average travel speed in the US, because it doesn't increase as much as you'd think in the >100km/h in many european places, even without significant amounts of speeding, due to cars scaling really badly at density with higher speeds.