Comment by jacoblambda

Comment by jacoblambda 2 months ago

Roundabouts aren't perfect but they greatly reduce the speed of traffic at the crossing point (while increasing the overall throughput of the intersection).

Without looking up statistics (and I'd love to be proven wrong here), I'd be willing to guess that roundabouts may result in some marginal increase in minor accidents but massively reduces fatalities or accidents that leave the pedestrian in the ICU.

Additionally with a roundabout the crossing can be moved a few cars down the street away from the roundabout itself so that cars can have line of sight to safely approach the crossing and pedestrians have time to react to incoming vehicles. On top of that proper placement of crossings allows a normal zebra crossing to be upgraded to a pelican, puffin, or toucan crossing without impeding flow of traffic within the roundabout.

smileysteve 2 months ago

For pedestrians, roundabouts also eliminate left turn lanes, saving ~9' of stroad width to cross and mean only looking one, predictable, direction at a time.

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cogman10 2 months ago

At high traffic times, they can make a pedestrian wait longer. Not so fun when it's cold out.
But otherwise somewhat easier to navigate.

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inetknght 2 months ago

1-lane roundabouts are OK

More than 1-lane and they're a disaster waiting to happen

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smileysteve 2 months ago

A disaster for cars, at a slower speed and similar direction than the comparable intersection (and no racing to/from from a light psychology).
So a disaster with significantly better outcomes than a red light runner (with a high speed side swipe or head collision)

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cogman10 2 months ago

Nah, 2 lanes are pretty manageable. Even for a pedestrian. You still only have traffic coming from one direction which makes it easy to see when you can cross.
From a car perspective, it's just a matter of getting in the right lane for the exit you want.

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rcpt 2 months ago

With roundabouts drivers only look to the left and don't come to a complete stop. If you're on foot trying to cross from the other direction good luck.

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jacoblambda 2 months ago

Yep. Hence the appeal of turning the intersection into a roundabout and pulling the stoplights 3-5 cars from the roundabout and only stopping traffic when pedestrians are present (i.e. puffin and pelican crossing style). It gives cars enough time to turn and then halt with a bright red stop light to catch their attention.

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- rcpt 2 months ago
  
  Roundabout + pedestrian stoplight is probably fine. I don't think I've ever seen one and I live not too far from where the article is written.
  Seems like it's still worse for pedestrians as they have to wait for the beg button.
  
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  jacoblambda 2 months ago
  
  Here's a link to the Massachusetts Dept of Transportation's guide on designing/building roundabouts:
  https://www.mass.gov/doc/massdot-guidelines-for-the-planning...
  It provides solid guidance on how roundabouts should approach crossings to minimize risk of accidents or collisions without impeding traffic.
  Probably the best graphic is on page 45, figure 5-13
  
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andrepd 2 months ago

Crosswalks before the entry to the roundabout, where drivers need to stop anyway; bonus points for a gentle speed hump. Am I missing something?

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- rcpt 2 months ago
  
  What kind of roundabout has a "stop anyway"?
  
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  jacoblambda a month ago
  
  Normally they are for pedestrian crossings. The stop for the incoming traffic will be near where the vehicles yield prior to entering the roundabout but the stop for outgoing traffic is several cars away to allow cars to continue moving in the roundabout.
  And because they are pedestrian crossings, they only go red when someone is walking across them and for a few seconds before and after. Which means in most cases they are green 90-95% of the time and only go red for less than a minute at a time.
  
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  gs17 2 months ago
  
  Some do have stop signs before you enter, but they should always have at least an implicit yield. Vehicles entering should be prepared to stop in case there's not room to enter the roundabout yet. The real issue with their suggestion is that only being able to cross "before the entry" wouldn't get you anywhere, you have to also cross where cars exit it!
  
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throw7 2 months ago

I'm not against circles in general, but (along with pedestrians) they aren't exactly bike friendly either.

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