As Dublin marks the opening of its 21st roundabout at state Route 161-Riverside Drive, it is a good time to take a look at whether Dublin's other roundabouts are meeting our expectations for improved safety.

As Dublin marks the opening of its 21st roundabout at state Route 161-Riverside Drive, it is a good time to take a look at whether Dublin's other roundabouts are meeting our expectations for improved safety.

The news is very good.

Dublin began its roundabout program in 2003 after a tragic crash at the Brand Road-Muirfield Drive intersection that claimed a young child's life.

Although the intersection was already slated for improvements, the tragedy fast-tracked the project and construction was completed in 2004.

Our city was looking for better ways to improve safety and traffic flow throughout Dublin, and our research indicated installing roundabouts would be the best solution. Twelve years later, we have the numbers to prove it.

At the top three most heavily-used roundabouts (Avery-Muirfield Drive/Post Road, Muirfield Drive/Brand Road and Emerald Parkway/Glendon Court), we have seen a 34 percent decrease in the overall crash rate and a 61-percent decrease in the severity of collisions since they were installed.

Those great numbers are in line with what the Federal Highway Administration is seeing nationally with roundabouts: a more than 90 percent reduction in fatalities and 35 percent reduction in all crashes.

You might ask why roundabouts have such a great safety record.

A traditional four-way intersection has 32 potential ways vehicles can collide. These are called conflict points.

A roundabout has just eight conflict points. That immediately cuts the chance of a crash by 75 percent.

Pedestrians face just two conflict points versus six in a traditional intersection, reducing their risk of a collision with a vehicle by 67 percent.

Roundabout crossings are also safer because traffic is moving 40- to 50-percent slower (about 20 mph) compared to vehicles approaching an intersection with a green light (35 to 40 mph). Thus, even when crashes do occur, damages and injuries tend to be much less severe.

There are many other benefits, too, such as reducing congestion by eliminating long delays at traffic lights and moving large amounts of traffic more efficiently. Less delay means less air and noise pollution from idling cars, and also saves both gasoline and time.

That's why you will see more roundabouts here in the future.

Construction of the Rings-Churchman roads roundabout is nearing completion.

Additionally, several more roundabouts are planned for the immediate future, including the Avery-Brand roads intersection, where construction of a roundabout is planned in 2017.

It might seem there are more roundabouts in Dublin than any other U.S. city, but Carmel, Ind., has that distinction with more than 90 roundabouts.

It is estimated there are more than 5,000 roundabouts in operation across the country. If you're interested in learning more, see www.roundaboutsusa.com.

Paul Hammersmith, Dublin's director of engineering, submitted the City Notes column.