In the early 1990s, multiple crashes and heavy congestion during peak traffic times were regularly occurring at the intersection of MD 144 and MD 94 in Lisbon. While no fatalities occurred, there were 15 personal injury crashes along with 18 property damage collisions from 1989 to 1992.
Instead of putting up a traffic signal to handle the average 9,000 vehicles on MD 94 and 6,000 on MD 144, the data caused Maryland Department of Transportation State Highway Administration (SHA) officials to decide on a relatively new traffic calming application—the roundabout. Featuring right turning, continuously moving lanes, the structure is designed to slow traffic and reduce congestion and crashes. While traffic signals stop traffic periodically, roundabouts encourage a continuous flow.
Opening in spring 1993, the roundabout led to a reduction in vehicle crashes. There were two personal injury crashes and seven property damage collisions from 1994 to 97 with no fatalities.
Since that opening a quarter of a century ago, roundabouts have been popping up across the state, including two on Fingerboard Road and one at MD 355 in Urbana. SHA maintains just under 90 with more planned in the coming months and years. There are nearly 200 others maintained by local and county governments and municipalities.
Charlie Gischlar, SHA spokesman, noted that roundabouts can be a safer alternative to four-way stops and other traffic control devices. “What happens with roundabouts is you are reducing high-speed angle crashes (also known as T-bone crashes), which are very, very dangerous,” he said. “You are slowing the traffic down and you are putting them in a constant circular motion and that does help reduce that conflict that is often very severe when there is a crash. Also, you are keeping traffic moving. Everyone is yielding to the left and proceeding to the right.”
The roundabouts have grown in popularity, Gischlar said, because motorists, pedestrians and bicyclists realized something had to be done. “With traffic volumes increasing around the area, there has to be a way now to reduce some of these conflicts,” he said. “I think people are starting to accept that roundabouts are a good traffic control device to install. There are certain areas where there is some reticence about it. They don’t think it is going to work They think it will be too much but after awhile, motorists then become familiar with it and a lot of them are OK with it.”
SHA oversees the roundabout at MD 80 by southbound I-270 ramps. Before the roundabout between 2005 to 2007, there were no fatalities, five personal injury crashes and five property damage collisions. After the roundabout was constructed in 2008, there were no incidents between its opening year to 2010.
The Frederick County Division of Public Works Project Manager David Olney noted the roundabouts at county intersections in Urbana did not replace existing conventional intersections. They were constructed as part of new subdivisions on land that was previously undeveloped. ‘Before’ crash data is not available for these intersections since there was no intersection before the roundabout construction.
The University of Maryland’s Center for Advanced Transportation Technology Laboratory provides the county with a limited amount of crash data between 1993 to 2015. No more current data has been released. “The available data suggests a low frequency of crashes in county roundabouts in the Urbana area,” Olney said. “A search of crash data collected in 2000 to 2015 identified only one crash in any of the county’s seven roundabouts. This crash was a rear-end collision that resulted in a non-incapacitating injury. Prior to 2000, there were no roundabouts in the Urbana area.”
Statewide, there have been no fatalities on SHA-maintained roundabouts from two or more vehicle crashes. There was a fatality in Montgomery County when an intoxicated driver crashed his vehicle.
Another county comparison on traffic data could be to look at the intersection at U.S. 15 at MD 464 in Point of Rocks. From 2004 to 2007, the intersection saw one fatality, 14 personal injury crashes and seven property damage collisions. After the permanent roundabout was installed in summer 2009, there were no fatalities, three personal injury crashes and 14 property damage collisions from 2009 to 2012. This section of U.S. 15 handles nearly 18,000 vehicles a day.
As of right now, SHA has no plans to put any additional roundabouts in the Urbana area, but officials are routinely evaluating intersections for increased traffic congestion and crashes.
“Our traffic engineers have a variety of tools in the safety tool kit,” Gischlar said. “We can put a signal up. We can out a roundabout in. We can put stop signs in. We can do any number of things. Each case is different. It has to be examined differently depending on what the application is. Sometimes a traffic signal is necessary (and) not necessarily a roundabout or vice versa or we could put turn lanes in to bypass traffic around through traffic. Roundabouts are something in our safety tool box that we do look at all the time with different intersections.”