Thursday, May 27, 2010

Roundabouts and pedestrians

Roundabouts are only a good idea if, along with the well-documented traffic improvements they bring, they improve things for pedestrians and bicyclists.

Walkinginfo.org, a clearinghouse for pedestrian activists, has a good summary of the issues:

Modern roundabouts by their design require motorists to slow down typically to less than 25 mph (40 km/h), and preferably 15 mph (25 km/h) to proceed through the intersection. The literature shows that, given a properly designed single-lane roundabout, motorist and pedestrian safety is almost always improved when compared to conventional intersections. Results regarding cyclist safety are somewhat mixed. Roundabouts have fewer conflict points and lower speeds compared to conventional intersections, resulting in a significant overall reduction in the severity of crashes for all users, although the frequency of some crashes may increase. Multi-lane roundabouts present some challenges to pedestrians, thus reducing the safety effects that roundabouts provide.

It appears that the basic design of a roundabout is pretty straightforward and should nearly always deliver the motor vehicle improvements. On the pedestrian and bicycle fronts, however, as Nathan points out, there can be good and bad implementations. Simply lowering vehicle speeds is good, but not enough. Thoughtful, pedestrian- and bicycle-friendly design is imperative.

5 comments:

Anonymous said...

From the link given, the only good way to do this is with the splitter island configuration. If you don't have enough room to do that, pedestrian safety is severely decreased compared to cars stopping at an intersection. Other comments regarding the vehicles moving slowly enough to "catch the motorist's eye" just seem to be an absurd argument and will hurt the advocacy for roundabouts. Even then, I don't know if crossing while cars are zipping through at even 15MPH can be considered safe. With a steady stream of cars, what's going to happen when someone stops for a pedestrian, and the whole circle backs up? How many accidents is that going to cause? All the pretty pictures show 2 or 3 cars driving calmly around a circle with plenty of room between them. Not very realistic. The information from the link: "The splitter islands at roundabouts allow pedestrians to cross one direction of traffic at a time. This is a significant advantage over conventional intersections. If motorists do not yield to pedestrians at the crosswalk, pedestrians must select a gap in traffic before crossing. If traffic flow is continuous, choosing a gap may become problematic"

Jass said...

My biggest problem with roundabouts and pedestrians is that they force you to cover a larger distance if your destination is diagonally across from you.

As for bikes, I have no problem with them. You might be interested in the way this roundabout was designed, bikes are given the choice to continue on the road or go on the sidewalk if they feel safer there (sidewalk riding is legal in california)

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=93720&sll=37.0625,-95.677068&sspn=36.368578,79.013672&ie=UTF8&hq=&hnear=Fresno,+California+93720&ll=36.81514,-119.736006&spn=0.000562,0.001206&t=k&z=20&layer=c&cbll=36.815183,-119.736172&panoid=uoJz0MwgbwMotg7VRtUSEA&cbp=12,45.59,,1,9.56

Heres one down the block:

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=93720&sll=37.0625,-95.677068&sspn=36.368578,79.013672&ie=UTF8&hq=&hnear=Fresno,+California+93720&ll=36.811488,-119.736233&spn=0.000566,0.001206&t=k&z=20&layer=c&cbll=36.811488,-119.736233&panoid=5wHKFepvQxfIe4YyYOgIJw&cbp=12,343.32,,1,8.75


In the image, youll note a BUNCH of orange cones. When these were installed 2 years ago (right when google visited), they were the first in the city, so officials were concerned that drivers wouldnt know what to do. The cones are no longer there.

Jass said...

Oh, heres another one, which also has the bike access....but terribly done (youd have to stop and make two sharp turns)

http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=93720&sll=37.0625,-95.677068&sspn=36.368578,79.013672&ie=UTF8&hq=&hnear=Fresno,+California+93720&ll=36.900289,-119.75805&spn=0.000565,0.001206&t=k&z=20&layer=c&cbll=36.900384,-119.758343&panoid=zwr_x-RBMhlAKl7-1mSUqg&cbp=12,8.65,,1,14.61

Anonymous said...

Hmm, that comment about "catching the motorist's eye" and the information below about visually impaired issues makes you think. So how can you realistically say you can design a newton center roundabout with a single lane to at least help some pedestrians let alone those who don't see very well? Is anyone going to say it makes sense to narrow down Center St. to one lane to make a roundabout effective?
From the same referenced link: "Multi-lane roundabouts that would be found on multi-lane roadways are not going to make these corridors work better for cyclists or pedestrians, but their lower operating speeds have some advantage. More work is required to ensure that people who are visually impaired can be well-accommodated at roundabouts."

Steve R said...

Anonymice:

Last I looked, both Centre and Beacon at the Newton Center intersection are one-lane before and after the intersection. There are turn/through lanes at the intersection itself, but the approaches are one-lane, which would make a one-lane roundabout a sensible solution.

The one remaining hitch could be the infrequent gaps for pedestrians... but would a pedestrian really need to wait longer than the current wait for a crosswalk signal? Hard to say. Right now, it's a long wait.

Always remember, too, about vehicle speeds: in vehicle-pedestrian collisions at 40 mph, >80% fatality rate; below 20 mph, <5% fatality rate. Vehicle-vehicle collisions <15mph rarely cause more than a little property damage.

So even if the raw number of accidents increased (which is highly unlikely), their severity would diminish dramatically.