Will Roundabout Intersections in Denver Reduce Car Accidents?
If changing the way you look at, approach, and drive through that busy intersection near home could save you from a minor or serious car accident, maybe it’s time to make a change.
Residents of Denver’s West Highland neighborhood will see the differences in several intersections as the Denver Public Works (DPW) Department starts turning them from ordinary, four-way, four-stop intersections into roundabouts, according to a report by StreetsBlogDenver writer David Sachs. DPW, which has been working on the plans for three years, will begin installing the “roundabout” traffic circles at three intersections on West 35th Avenue in July.
The city will install the bright yellow curbs at Julian, Newton, and Raleigh streets. Engineers will also be removing some of the stop signs pinning each intersection.
Normal intersections, where two streets meet, have four lanes going in opposing directions. The most dangerous place of that intersection for traffic accidents is likely the dead center, where cars and trucks continuously zoom past each other, leaving only a couple of feet in between.
Install a 12-foot-wide circular curb in the middle of that intersection, though, and the traffic patterns change. Instead of going straight through the juncture, you’ll have to slow down, circle one-half of the roundabout and continue on in. To take a left turn, you’ll have to go the long way around. Veer right and circle the roundabout three-quarters of the way.
DPW is installing the circles to calm traffic and augment 35th Avenue’s role as a neighborhood bikeway, Sachs reported. The roundabouts force motor vehicles to slow down and allow bikers to move through without having to come to a complete stop. As a result, all of the traffic is moving at a consistent, safe speed.
Although Denver has several larger roundabouts, the small-scale installations are a new tool for traffic engineers and, at $11,000 apiece, are a relatively cheap, quick tool to re-engineer an intersection.
Roundabouts have an established track record for improving street safety.
A Case in Point: Golden, Colorado
Traffic engineering researchers at the Texas A&M Transportation Institute determined that roundabouts can reduce delays, shorten travel time, and reduce speeds on roads where they’re implemented. The structures replace traditional intersections controlled by traffic signals and reduce the time cars and trucks spend waiting for their turn to cross.
The structures also improve safety by preventing some auto accidents and reducing congestion at these intersections. Because cars and trucks enter and exit roundabouts by using right-hand turns only, they also manage to reduce the number of severe crashes that can occur.
The Texas A&M Institute cites a traffic corridor in Golden, Colorado, as a prime example of roundabouts’ effectiveness. Traffic engineers there revamped half a mile of roadway by replacing four traffic signal-controlled intersections with roundabout structures. Researchers compared before- and after-project statistics and found that while the speed between intersections was reduced, motorists saw their travel times reduced from 78 seconds to 68 seconds.
Before installation, delays averaged about 28 seconds, with some reaching 188 seconds. Afterward, average delays dropped to 13 seconds, and the longest was only 40 seconds.
Traffic volumes increased from 11,500 to 15,500 cars and trucks per day, but the number of accidents, per year, dropped from 123 to 19.
The number of car accidents with bodily injuries dropped from 31 in the three years before the installation to only one in the 4.5 years afterward, a 93 percent decline. The research abstract published on the Texas A&M Institute’s Web page did not mention the Golden road intersections featured in its research.