Roundabouts offer improved safety over other at-grade intersection forms primarily because roundabouts have fewer conflict points, slower speeds, and easier decision making.
Roundabouts are geometrically designed to reduce vehicle speeds to generally 25 mph or less, and all turns are right turns. This significantly reduces the severity of crashes over those at traditional intersections. Crashes that do occur are typically low-speed, sideswipe crashes rather than high-speed T-bone collisions that can occur at traditional intersections especially with left-turn movements.
Roundabouts also improve pedestrian safety due to the slow speeds and by providing a median refuge area. This allows for two simple crossings of one-way traffic.
In September 2023, PennDOT released data for 42 roundabouts on state routes at intersections that were previously stop- or signal-controlled. These roundabouts were reviewed based on having at least three years of data available before and after the roundabout's installation. These 42 comprise all the roundabouts on state routes that met the review parameters. Department data based on police-submitted crash reports spanning the years 2003 through 2022 shows:
- Crashes involving suspected serious injuries were reduced by 24 percent;
- Crashes involving suspected non-serious injuries were reduced by 51 percent; and
- The total number of crashes dropped three percent.
In addition to the 42 roundabouts meeting the review criteria, 36 other roundabouts have been installed on state routes.
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- Allegheny County:
- Route 3070 (Ewing Road) and Business Route 376 Ramp, opened in 2011.
- Beaver County:
- Route 68 (Adams Street), Route 1034 (Brighton Avenue) and Route 6018 (Brighton Ave./Rhode Island Ave.), opened in 2011.
- Berks County:
- Route 222 and Route 662, opened in 2018.
- Route 73 and Lynx Drive, opened in 2019.
- Route 73 and Oley Road, opened in 2019.
- Bucks County:
- Route 2043 (Trevose Road) and Somerton Road, opened in 2012; and
- Route 213 (Bridgetown Pike/Maple Avenue) and Route 2010 (Bridgetown Pike), opened in 2016.
- Route 4049 (Tollgate Road) and Old Bethlehem Pike, opened in 2019.
- Butler County:
- Route 3024 (Glen Eden Road), Powell Road and Freshcorn Road, opened in 2015; and
- Route 228 and SR 2005 (Saxonburg Blvd.), opened in 2018.
- Chester County:
- Route 82 (Doe Run Road) and Unionville Road, opened in 2005;
- Route 52 (Lenape Road), S. Wawaset Road and Lenape Unionville Road, opened in 2014; and
- Route 3062 (Strasburg Road), Romansville Road and Shadyside Road, Opened in 2017.
- Crawford County:
- Route 6/19 (Main Street) and Route 198 (South Street), opened in 2017; and
- Route 6/19 (Main Street) and Route 198 (Brookhouse Street), opened in 2017.
- Route 6/322 and Route 19/98, opened in 2019.
- Cumberland County:
- Route 34 (Spring Road), Route 1007 (Sunnyside Drive) and Mountain Road, opened in 2014; and
- Route 2004 (W. Lisburn Road) and Grantham Road, opened in 2018.
- Route 2017 (Lisburn Road) and Rossmoyne Road, opened in 2019.
- Dauphin County:
- Route 39 (Linglestown Road) and Route 3019 (Mountain Road), opened in 2011;
- Route 322 (Governor Road) and Homestead Lane, opened in 2016; and
- Route 322 (Governor Road) and Meadow Lane, opened in 2016.
- Delaware County:
- Route 1023 (N. Newtown Street) and Route 1046 (St. Davids Road), opened in 2008; and
- Route 320 (Chester Road), Rutgers Avenue and Fieldhouse Lane, opened in 2014.
- Erie County:
- Route 19 (High Street) and Route 97, opened in 2014; and
- Route 5 and Route 4016 (Millfair Road), opened in 2018.
- Luzerne County:
- I-81 Exit 178, Airport Road interchange (three roundabouts), opened in 2015;
- Route 2008 (Middle Road) and Espy Street, opened in 2017;
- Route 415, Church Street, Lake Street and Main Street, opened in 2018; and
- Route 2008 (Middle Road) and Kosciuszko Street, opened in 2018.
- Route 2008 (Middle Road) and Prospect Street, opened in 2019.
- Mercer County
- Route 718 (Dock Street) and Connelly Boulevard, opened in 2018.
- Monroe County
- I-80 Exit 310 and Route 2028 (Broad Street), opened in 2018.
- Montgomery County:
- Route 29 (Gravel Pike) and Route 73 (Big Road), opened in 2009.
- Philadelphia County:
- Route 4013 (Park Drive) and Route 4015 (Walnut Lane), opened in 2018.
- Washington County:
- Route 519 (two connected roundabouts) - Route 519 and Brownlee Road, and Route 519 and Thompson Eighty Four Road, opened in 2015; and
- I-70 Exit 32 and Route 2040 (Wilson Road), opened in 2018.
- Wyoming County:
- Route 1017 (College Ave.) and Edwards Lane, opened in 2019.
- York County:
- Route 116 (Main Street) and Hanover St. and Roths Church Road, opened in 2007; and
- Route 74 (Delta Road) and Bryansville Road, opened in 2008.
Roundabouts typically carry about 30 percent more vehicles than similarly sized signalized intersections during peak traffic conditions. During off-peak conditions, roundabouts cause almost no delay, unlike traffic signals which can cause delay to side street and traffic turning left from the major street. The increased capacity and efficiency of roundabouts is due to the generally continuous slow-flowing nature of entering vehicles yielding to circulating vehicles rather than waiting for a signal to turn green. It should be emphasized that entering vehicles are required to yield to pedestrians and the circulating traffic, which commonly requires stopping, especially during peak traffic conditions.
Because Pennsylvania is on track to install more roundabouts in the coming years, we've created this video to show you just how easy they are to navigate. After you watch the video, you'll know how to use both single and multi-lane roundabouts whether in a vehicle, on a bicycle, or on foot. The primary keys for motorists to navigating a roundabout are to slow down, yield to pedestrians, and yield to the circulating traffic.
Swarthmore Borough in Delaware County constructed a roundabout on Chester Road (SR 0320). The video below gives an overview of the development and execution of the roundabout project to create a safer route for drivers and pedestrians. (Courtesy of McMahon Associates)