Roundabouts continue to pop up around the state as a safer alternative to traditional intersections.
Two roundabouts were opened in the second half of 2018 in PennDOT's Allentown-based District 5 – covering Berks, Carbon, Lehigh, Monroe, Northampton, and Schuylkill counties.
In July, a roundabout was installed at the intersection of US 222 and PA 662 in Richmond Township, Berks County. The $6.6 million project replaced a signalized intersection with a modern roundabout, along with widening US 222 to four lanes at the roundabout approaches.
And in November, the district's third roundabout opened at the intersection of Broad Street, River Road, Foxtown Hill Road, and the Interstate 80 Exit 310 ramps in Smithfield Township, Monroe County. Although this roundabout is open, crews continue to work on the center and approach islands and all work is expected to be complete in the spring.
The signalized intersection was replaced with a modern roundabout, and the $14.13 million project also included replacing the Exit 310 on-ramp bridge to I-80 east in Smithfield Township, and the Exit 310 off-ramp from I-80 west in Delaware Water Gap Borough. Both ramps traverse I-80.
PennDOT recently reviewed data for 11 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. Department data based on police-submitted crash reports spanning the years 2000 through 2017 shows:
- Fatalities were reduced by 100 percent (from two to zero);
- Serious injuries were reduced by 100 percent (from seven to zero);
- Minor injuries were reduced by 95 percent (from 19 to one);
- Possible/unknown severity injuries were reduced by 92 percent (from 49 to four);
- Crashes causing only property damage decreased by 2 percent (from 49 to 48); and
- The total number of crashes dropped 47 percent (from 101 to 54).
The main characteristics of a modern roundabout include: generally circular shape; yield signs at the entrances; geometry that forces slower speeds; and counterclockwise circulation of traffic. Also, unlike traffic signals, roundabouts do not depend on electricity to function, so they are not susceptible to power outages.
Roundabouts are frequently installed to address intersections with safety issues but may also be installed to improve traffic flow as well as other reasons such as traffic calming, and to facilitate pedestrian mobility.
Although roundabouts are safer and typically more efficient than traditional signalized intersections, in many cases they may not be the best option due to topography or other reasons, such as property impacts, capacity issues and proximity to other intersections.