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Traffic calming doesn't make roads less safe. Advocates of traffic calming measures aren't trying to literally make roads as unsafe as parking lots. What makes

by learc83 10y ago

Traffic calming doesn't make roads less safe. Advocates of traffic calming measures aren't trying to literally make roads as unsafe as parking lots. What makes parking lots unsafe is the constant threat of someone pulling out in front of you, no one is advocating simulating that. Think about roundabouts, they force you to slow down because they prevent you from driving directly though an intersection. They are statistically much safer than 4 way stops.

wvenable 10y ago
I agree that neighborhood roads should have roundabouts and so on. But that doesn't apply to major arteries, highways, etc.
- labster 10y ago
  I would agree, but my father used to drive a bottled water delivery truck. And he's seen lots of neighborhoods where roundabouts are simply not built large enough to accommodate anything with more than two axles. In California, roundabouts tend to be added into new construction, but squeezed into a space that is no larger than a normal intersection.
  - oblio 10y ago
    If they're designed properly, they should be low, almost the same height as speed bumps. That way something with 16 wheels can go straight over them while regular cars will probably go around them.
Ntrails 10y ago
>Think about roundabouts, they force you to slow down because they prevent you from driving directly though an intersection. They are statistically much safer than 4 way stops. That's not entirely true, with half decent vision I can drive straight onto and off the roundabout again. Certainly in a 30/40mph limit I don't have to slow down particularly. The point of roundabouts isn't to slow people down, it's to keep traffic moving efficiently and safely. Four way stops are just obviously an awful solution that I've never understood
- emj 10y ago
  Depends on the size of the roundabout, some are designed for 40 mph others for a more sane 20 mph.
  - Ntrails 10y ago
    I mean, a roundabout is a system for efficient "giving way". 20mph is only "more sane" when a roundabout is in a low speed limit area. We've got plenty of them on 60mph zones - you've got no interest in having cars slow down and accelerate again when not necessary (if nothing else because it's a waste of energy as well as time).
    - arghwhat 10y ago
      How is it efficient for "giving way"? If one entry is highly traficated, entries between the traficated one and the popular exits cannot get in.
- vvillena 10y ago
  The second benefit of well-made roundabouts is that they impede head-on and T-bone collisions. All accidents become side-by-side accidents.
arghwhat 10y ago
By god, I hate roundabouts. Not because I have to slow down. If your exit is 45-90 degrees to the right (which a few of the roundabouts I have to go through are), you can commonly go in a straight line towards it without slowing down the slightest anyway, and going in as straight a line as possible is encouraged over here to make your intentions clear. However, I feel much less safe going through a traficated, small-radius two-lane roundabout than I do going through a traficated intersection (making a turn or not). First of all, you have to find a gap, which is stressful and entirely unnecessary in a normal intersection. Traffic usually mean that just don't get a large enough gap to get in without accelerating hard, which isn't really safe. If you want an exit that is not the first (sometimes also the second), you have to use the inner lane, meaning that you need to find a gap in two lanes, rather than one. It seriously lacks some fair scheduling. Depending on the roundabout, exiting can only be done by going "LEEROY JEENKIIIINS". Your mirrors point at nothing useful due to the turn of the roundabout, so the lane change back out involves going fast forward to the left, with your neck twisted as far as you can back to the right. Everyone is moving at their own random, highly variable pace, so a quick orientation is immediately invalidated. On a straight road, you can rely almost entirely on your mirrors so your peripheral vision still covers what's ahead of you. Collisions between cars are likely milder, as the vehicle velocity is limited by the roundabout geometry, but side collisions are awful, and the chance of collision seems much higher, feeling like a game of Russian roulette. I'm normally (over)confident behind the wheel, with no problem driving like an idiot, around other driving like idiots, and have several hundred thousand kilometers of driving experience, but I get uncomfortable and stressed in those roundabouts. Some two-lane roundabouts have fixed this by drawing the lines so that the lanes spiral out, with the outer lane going to the next exit, and the inner lane going to the one after it. In this way, going around the roundabout is a constant lane change to the left with no one beside you, and an exit is simply keeping your lane. This helps a lot, but is by no means common. Entry still sucks, though
- learc83 10y ago
  >Collisions between cars are likely milder, as the vehicle velocity is limited by the roundabout geometry, but side collisions are awful, and the chance of collision seems much higher, One study of 17 intersections found an 84% reduction in injury accidents. And a 100% reduction in fatal accidents. And every study I've seen is pretty similar in terms of injuries avoided.
AnthonyMouse 10y ago
> Traffic calming doesn't make roads less safe. It absolutely does when you measure it against the alternatives instead of the status quo. The only way you can get an apparent benefit from it is through people overcompensating for danger. People are driving 30MPH, you add some danger, people overcompensate for the danger by driving 25MPH, so the result is as though people were driving 28MPH on the original road. You call this a benefit. The problem is that it's crazy. You're designing an intentional safety reduction and paying the full cost of it just so that people will overcompensate for it. What you should be doing is designing a safety improvement that people will undercompensate for. Make the road as safe to drive at 35MPH as it was at 30MPH, but don't make that fact obvious, so that people only drive 2MPH faster even though the road is 5MPH safer. Then people drive 32MPH and the safety level is as though they were driving 27MPH on the original road. Compared to traffic calming you have a safer road and people get where they're going 7MPH faster.
- aoeusnth1 10y ago
  Safer for drivers - maybe. Safer for pedestrians? No.
- learc83 10y ago
  Traffic calming isn't decreasing the safety of a road, it's decreasing the perceived safety of driving at higher speeds. >Make the road as safe to drive at 35MPH as it was at 30MPH, but don't make that fact obvious What would that even look like? What would you do to increase the safe speed of road? You'd widen the lanes, limit access etc... All of these things are antithetical to making a road safer for non-motorists.
  - AnthonyMouse 10y ago
    > Traffic calming isn't decreasing the safety of a road, it's decreasing the perceived safety of driving at higher speeds. It is decreasing the actual safety of driving at higher speeds. And at lower speeds for that matter. The hope is that people will overcompensate for the danger, so that the safety improvement from driving at lower speed is more than the safety loss from the inherently dangerous design. That is obviously not a desirable trade-off, even when that actually happens. > What would that even look like? What would you do to increase the safe speed of road? You'd widen the lanes, limit access etc... All of these things are antithetical to making a road safer for non-motorists. You separate the motorists from the non-motorists. Put sidewalks and bike lanes on the opposite side of each building from the road, so that a building has motorist access on the north and east and non-motorist access on the south and west. Then the building to the north has motorist access on the south and pedestrian access on the north etc. Build pedestrian tunnels or bridges at busy intersections so that pedestrians and cyclists are never in the road at all. Houston has a system of underground pedestrian tunnels: https://en.wikipedia.org/wiki/Houston_tunnel_system https://en.wikipedia.org/wiki/Houston_tunnel_system None of those pedestrians has ever been hit by a car at any speed.

by learc83 10y ago

wvenable 10y ago

I agree that neighborhood roads should have roundabouts and so on. But that doesn't apply to major arteries, highways, etc.

labster 10y ago
I would agree, but my father used to drive a bottled water delivery truck. And he's seen lots of neighborhoods where roundabouts are simply not built large enough to accommodate anything with more than two axles. In California, roundabouts tend to be added into new construction, but squeezed into a space that is no larger than a normal intersection.
- oblio 10y ago
  If they're designed properly, they should be low, almost the same height as speed bumps. That way something with 16 wheels can go straight over them while regular cars will probably go around them.

Ntrails 10y ago

>Think about roundabouts, they force you to slow down because they prevent you from driving directly though an intersection. They are statistically much safer than 4 way stops. That's not entirely true, with half decent vision I can drive straight onto and off the roundabout again. Certainly in a 30/40mph limit I don't have to slow down particularly. The point of roundabouts isn't to slow people down, it's to keep traffic moving efficiently and safely. Four way stops are just obviously an awful solution that I've never understood

emj 10y ago
Depends on the size of the roundabout, some are designed for 40 mph others for a more sane 20 mph.
- Ntrails 10y ago
  I mean, a roundabout is a system for efficient "giving way". 20mph is only "more sane" when a roundabout is in a low speed limit area. We've got plenty of them on 60mph zones - you've got no interest in having cars slow down and accelerate again when not necessary (if nothing else because it's a waste of energy as well as time).
  - arghwhat 10y ago
    How is it efficient for "giving way"? If one entry is highly traficated, entries between the traficated one and the popular exits cannot get in.
vvillena 10y ago
The second benefit of well-made roundabouts is that they impede head-on and T-bone collisions. All accidents become side-by-side accidents.

arghwhat 10y ago

By god, I hate roundabouts. Not because I have to slow down. If your exit is 45-90 degrees to the right (which a few of the roundabouts I have to go through are), you can commonly go in a straight line towards it without slowing down the slightest anyway, and going in as straight a line as possible is encouraged over here to make your intentions clear. However, I feel much less safe going through a traficated, small-radius two-lane roundabout than I do going through a traficated intersection (making a turn or not). First of all, you have to find a gap, which is stressful and entirely unnecessary in a normal intersection. Traffic usually mean that just don't get a large enough gap to get in without accelerating hard, which isn't really safe. If you want an exit that is not the first (sometimes also the second), you have to use the inner lane, meaning that you need to find a gap in two lanes, rather than one. It seriously lacks some fair scheduling. Depending on the roundabout, exiting can only be done by going "LEEROY JEENKIIIINS". Your mirrors point at nothing useful due to the turn of the roundabout, so the lane change back out involves going fast forward to the left, with your neck twisted as far as you can back to the right. Everyone is moving at their own random, highly variable pace, so a quick orientation is immediately invalidated. On a straight road, you can rely almost entirely on your mirrors so your peripheral vision still covers what's ahead of you. Collisions between cars are likely milder, as the vehicle velocity is limited by the roundabout geometry, but side collisions are awful, and the chance of collision seems much higher, feeling like a game of Russian roulette. I'm normally (over)confident behind the wheel, with no problem driving like an idiot, around other driving like idiots, and have several hundred thousand kilometers of driving experience, but I get uncomfortable and stressed in those roundabouts. Some two-lane roundabouts have fixed this by drawing the lines so that the lanes spiral out, with the outer lane going to the next exit, and the inner lane going to the one after it. In this way, going around the roundabout is a constant lane change to the left with no one beside you, and an exit is simply keeping your lane. This helps a lot, but is by no means common. Entry still sucks, though

learc83 10y ago
>Collisions between cars are likely milder, as the vehicle velocity is limited by the roundabout geometry, but side collisions are awful, and the chance of collision seems much higher, One study of 17 intersections found an 84% reduction in injury accidents. And a 100% reduction in fatal accidents. And every study I've seen is pretty similar in terms of injuries avoided.

AnthonyMouse 10y ago

> Traffic calming doesn't make roads less safe. It absolutely does when you measure it against the alternatives instead of the status quo. The only way you can get an apparent benefit from it is through people overcompensating for danger. People are driving 30MPH, you add some danger, people overcompensate for the danger by driving 25MPH, so the result is as though people were driving 28MPH on the original road. You call this a benefit. The problem is that it's crazy. You're designing an intentional safety reduction and paying the full cost of it just so that people will overcompensate for it. What you should be doing is designing a safety improvement that people will undercompensate for. Make the road as safe to drive at 35MPH as it was at 30MPH, but don't make that fact obvious, so that people only drive 2MPH faster even though the road is 5MPH safer. Then people drive 32MPH and the safety level is as though they were driving 27MPH on the original road. Compared to traffic calming you have a safer road and people get where they're going 7MPH faster.

aoeusnth1 10y ago
Safer for drivers - maybe. Safer for pedestrians? No.
learc83 10y ago
Traffic calming isn't decreasing the safety of a road, it's decreasing the perceived safety of driving at higher speeds. >Make the road as safe to drive at 35MPH as it was at 30MPH, but don't make that fact obvious What would that even look like? What would you do to increase the safe speed of road? You'd widen the lanes, limit access etc... All of these things are antithetical to making a road safer for non-motorists.
- AnthonyMouse 10y ago
  > Traffic calming isn't decreasing the safety of a road, it's decreasing the perceived safety of driving at higher speeds. It is decreasing the actual safety of driving at higher speeds. And at lower speeds for that matter. The hope is that people will overcompensate for the danger, so that the safety improvement from driving at lower speed is more than the safety loss from the inherently dangerous design. That is obviously not a desirable trade-off, even when that actually happens. > What would that even look like? What would you do to increase the safe speed of road? You'd widen the lanes, limit access etc... All of these things are antithetical to making a road safer for non-motorists. You separate the motorists from the non-motorists. Put sidewalks and bike lanes on the opposite side of each building from the road, so that a building has motorist access on the north and east and non-motorist access on the south and west. Then the building to the north has motorist access on the south and pedestrian access on the north etc. Build pedestrian tunnels or bridges at busy intersections so that pedestrians and cyclists are never in the road at all. Houston has a system of underground pedestrian tunnels: https://en.wikipedia.org/wiki/Houston_tunnel_system https://en.wikipedia.org/wiki/Houston_tunnel_system None of those pedestrians has ever been hit by a car at any speed.