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Traffic deaths are quite literally one of the two leading causes of death of children in the United States, so in this case, yeah, actually thinking of the chil
by davidw 2y ago
Traffic deaths are quite literally one of the two leading causes of death of children in the United States, so in this case, yeah, actually thinking of the children makes some sense.
- m463 2y agoNote the way to do this is to follow engineering rules. Take the 85th percentile rule. If you take a neighborhood road and change it from 40mph to 25mph in an attempt to "save the children", you can easily make it more dangerous. The 85th percentile rule figures how fast people go on a road, and sets an appropriate speed limit that people naturally follow. Attempting to set a speed limit too low or too high leads to a wide speed variance, which makes the road more dangerous.
- davidw 2y agoOr we could actually build slower, safer streets that are that way by design, rather than relying on signs. And where roads need to be fast and move a lot of cars, separate them out from other uses.
- m463 2y agoand set speed limit 5-10 mph below design speed for maximum safety.
- maxerickson 2y agoPeople go the speed they are comfortable with, not the speed on the signs. You have to design for the speed you want.
- m463 2y agocorrect.
- durkie 2y agoHow does setting a speed limit "too low" make a road more dangerous?
- m463 2y agoSafest roads have the speed limit 5-10 mph below the road design speed. see fig 4 on speed variance: https://www.fhwa.dot.gov/publications/research/safety/17098/003.cfm https://www.fhwa.dot.gov/publications/research/safety/17098/... going faster or slower than average traffic speed shows markedly greater accident rate. note that this can apply not only to speed limits, but things like express lanes going different speeds than other lanes
- durkie 2y agoBut you're saying the speed limit (being too high or low) makes the road dangerous. Aren't the people driving their cars too fast making the road dangerous?
- Leif24 2y agoA great many people when they see a open straight road with little obstacles or pedestrians will go 45-50 MPH. A great many people when they see a 15 MPH sign will go 20 MPH. Pair that low speed limit with a "fast" road and you will end with many people going 45 MPH and many people going 20 MPH. This variance in speed, with some people going much slower than others can be more dangerous than if most went the same speed - e.g. if the limit were 45 MPH. You are correct that people driving too fast make the road dangerous, but so does people driving too slow. Generally, from a safety point of view, you want the slowest speed at which almost everyone will actually drive at, as large variance in speed between drivers is dangerous. I think this is what the parent post was getting at: a speed limit too fast OR too slow will increase the number of accidents, keeping in mind that there will always be at least some drivers speeding.
- david-gpu 2y ago> You are correct that people driving too fast make the road dangerous, but so does people driving too slow. It's accurate to say that people driving too fast are extra dangerous when there are slower vehicles in the road. The danger is still caused by the people driving too fast, not by those driving slowly, though. Speed kills.
- bryanlarsen 2y agoIn my personal experience, automated speed cameras are way more effective than traffic calming.
- dghlsakjg 2y agoI live in BC, where speed cameras are banned by law. Right next door is Alberta. Last time I was in Edmonton, known for extremely car centric design, wide roads, ample highways, etc. I was shocked by how much slower people drove, and as a result, how much safer driving was in general. You only have to get slapped with a fine a few times before you start learning to control your speed.
- owlbite 2y agoI'd go further and say automated average speed cameras are the most effective I've seen. Point speed cameras just get marked on a map and cause sudden braking and acceleration to dodge them - this can be effective at particular danger spots, but I always feel the average speed cameras in the UK are far more effective at changing driver habits in general.
- oblio 2y agoYeah, but those probably cost more and don't make for a nice environment outside of cars. Traffic calming can be super cheap and it makes for a super pleasant environment for everyone.
- bryanlarsen 2y agoTraffic calming is usually more expensive than speed cameras. A speed bump isn't expensive but people are usually talking about stuff like bump outs and raised intersections and protected bicycle lanes and wide sidewalks when they are talking about traffic calming. Those are six figures per intersection. Cameras are low five figures.
- oblio 2y agoTraffic calming can be literally some poles or some pots with plants in them. It's the cheapest form of "infrastructure" after paint.
- bluecalm 2y agoThe problem is that people are naturally very bad drivers and are especially bad at judging what safe speed is. We already know it's hopeless to teach them so what is left are traffic calming measures, heavy handed enforcement and technology (automatic speed limiters in cars). Setting speed limits to speed people choose is a terrible idea.
- josephcsible 2y ago> Setting speed limits to speed people choose is a terrible idea. The point of the Solomon curve is specifically that that isn't true.
- bluecalm 2y agoPeople naturally choose speeds according to how safe they feel not how safe it is for everyone else. If you have a residential area road which is straight and wide enough to go fast people will choose higher speed than on a narrow road. This proves it doesn't work unless you only care about safety of people in cars (which Salomon curve seems to based on meaning it's meaningless for road design with the exception of highways).
- occz 2y agoI don't think I've ever heard someone argue that the 85th percentile rule is actually a good invention - it's a disaster that codifies the behaviour of speeding drivers. I agree that merely lowering speeds without changing the design speed is a bad move, though.
- blackeyeblitzar 2y agoTo me that sounds like a safetyist argument. Even if the number of deaths are high in total count, it may not matter when you consider the trade offs. For example if everyone spends an hour more in traffic each day - which is what the effect of “calming” has been in my experience - you’re causing an impact that is worse than the small number of deaths in my city. That delay and damage to our life quality matters, and needs to be weighed against the rare deaths. Cars are very safe today and are getting much safer. Even basic cars come with many features to avoid accidents now. We will probably see deaths per mile driven go down on its own, without the need for malicious road design.
- naniwaduni 2y agoSlowing down insidiously shaves away at your lifespan too, it just doesn't produce exciting catastrophic life loss events.
- david-gpu 2y agoBy that same logic, distance insidiously shaves away at your lifespan and we should build mixed-use walkable neighborhoods so that we can quickly reach our everyday destinations rather than causing traffic every time we want to get anywhere.
- naniwaduni 2y agoIt does! We should all live in NYC!
- ryukafalz 2y ago> Cars are very safe today and are getting much safer. For their occupants, sure. For those outside cars (and remember, children can't drive) not so much: https://www.nbcnews.com/news/us-news/americas-cars-trucks-are-getting-bigger-are-front-blind-zones-children-rcna52109 https://www.nbcnews.com/news/us-news/americas-cars-trucks-ar...
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