Wednesday, May 19, 2010

Could a roundabout have saved Andy von Guerard?

Commenting on the TAB blog, Peter Furth thinks outside the signalized intersection box for an infrastructure change that might have made a difference on Monday: the roundabout.

But, first, a refresher on what a roundabout -- a modern roundabout -- is and isn't. A modern roundabout is a circular intersection that a) requires entering users to yield to traffic already in the circle and b) is designed with a tight enough curve to slow all traffic to 30 MPH or less. It is not a traditional, Horace James-type rotary, which is designed for high-speed entry into and through the circle.

A modern roundabout is safer than old-fashioned rotaries and signalized intersections because all traffic slows to a narrow range of less lethal speed and because those navigating the roundabout have fewer decisions to make. The modern roundabout reduces the number of points of potential conflict by up to 75% compared to a signalized intersection.

Less technically, a modern roundabout requires a cooperative approach to navigating an intersection compared to a signalized intersection, where motorists proceed when they have a right that has been withdrawn from other drivers competing for the right to proceed. Drivers in a modern roundabout are presented with the responsibility to determine when it's safe to proceed, while creating opportunities to do so.

So, what does this have to do with the fatal collision at Comm. Ave. and Lowell/Homer? Had the intersection been configured as a modern roundabout, there wouldn't have been the same calculus about or the same incentives for von Guerard's ultimately fatal behavior. Approaching a modern roundabout, von Guerard would not have been gambling if the light cycle provided him enough time. Instead, he would have looked into the intersection to see when the next gap would open up.

Perhaps more importantly, the cost/benefit analysis that von Guerard got so badly wrong (and every red-running biker or driver makes) would have been different. He wouldn't have faced the wait for a complete light cycle to proceed. In a modern roundabout, von Guerard would have been able to proceed as soon as a gap opened.

In a modern roundabout, what other users of the intersection are doing and going to do is much clearer. And, the wait to continue is shorter.

Note that the last sentence didn't end "shorter for bikers." Modern roundabouts are better for everyone. Traffic flow through a modern roundabout improves by up to 50%. If anything, many bicycle advocates are worried about bicycle navigation through them. (I'll take up that issue in another post.)

In one sense, pedestrian and bicyclist red-running impatience with signalized intersections is just a symptom of the horrible inefficiency of the green-yellow-red cycle for everyone. As I've written in other posts, cars are required to stop too often and for too long. Stopping (and then starting again) wastes fuel, wears out cars, dumps pollutants in our neighborhood, creates driver impatience, wastes driver time, &c. The goal should be to reduce speeds generally and to reduce speeds where there is the potential for conflict -- intersections and crosswalks, in particular -- to a slow enough speed that cars can stop and yield if necessary without danger or drama.

Roundabouts don't solve all problems. There are going to be intersections where the traffic flow is beyond the design limits of a roundabout. Roundabouts don't create traffic calming between intersections (though the may have an indirect benefit compared to stop signs or lights). Pedestrian-actuated signals may be required to slow and then stop traffic at mid-block crosswalks, where a roundabout would not be indicated. Stop signs are effective where right-of-way is contested. &c.

But, we've got a whole bunch of signalized intersections where traffic is inefficiently managed, where the appeal of pedestrian jay-walking and biker and motorist red-running is high, where we're jamming up traffic when we don't have to. Roundabouts in those intersections would be better. And, the intersection of Comm. Ave. and Lowell/Homer is one of those intersections.

If Andy von Guerard ran the light because he wanted to exempt himself from the inefficiency of the traffic light, he paid the ultimate price for his bad judgment. But, that didn't make him wrong about the intersection, just unlucky.


dr2chase said...

Do you know either the traffic flow at that intersection, or some local examples of the different sorts of roundabouts?

I ask because Belmont has three (that come to mind), one with relatively heavy traffic, two not so much. The newest one gets the most traffic (I think) and is not bad at all on a bicycle, but may not have the capacity required for a major intersection. I worry a bit that the higher capacity roundabouts might not be so ped and bike friendly, despite the assurances of the highway experts (who don't exactly have a good track record of delivered bike/ped friendliness).

Newest rotary, intersection of Grove and Blanchard

Steve R said...

Dr2, that looks like a great example of a roundabout! Nice clean sight-lines, a tight circle to slow traffic, clearly marked pedestrian crossings some distance from the circle, with 1/2-way refuges, traffic separators. Yes, this is what we're looking for. I may bike off and see it someday soon.

Traffic counts on Comm. Ave. aren't as high as many of the other arteries in Newton; bike counts in a bike accomodation plan from '04 included counts for Comm. Ave. at 14,000--but I don't know where (or when) the counts took place or whether that # was averaged over the whole length in Newton.

Nathan Phillips said...

dr2chase - that roundabout looks good, except no bike lane. If the intention is for bikers to take the lane, then sharrows on the approach and in the roundabout would be a relatively simple solution. Of course that might be out of context for this particular roundabout if there are no bike accommodations on the connecting roads to begin with.

dr2chase said...

Funny you should mention sharrows. Yes, there are bike accommodations on the main streets, including sharrows on the streets themselves. However, Blanchard (the street to the right) I don't recommend to anyone; yes, it has sharrows, but it curves, the sight lines are not good, and the traffic is heavy and fast. It's a good deal less stressful, and about as fast (depending upon where you are going) to exit the roundabout left (Washington St) and take a right on Bright St just outside the picture.

Sharrows don't do much for me. It's a bit too subtle for the worst of the car drivers (seriously, we had people in town inquiring about the "graffiti" on the road).