Roundabouts

Roundabouts keep traffic moving. The major delay on a person's morning or evening commute is usually the time spent sitting at traffic signals. Eliminating the need to stop and wait reduces delay.

Using a roundabout is much the same as making a right turn from a stop sign. At a traffic signal, a right-turning driver stops at the stop bar, looks for conflicting traffic coming from the left, chooses an acceptable gap in the traffic flow, and then turns right onto the cross street. At a modern roundabout, the oncoming driver approaches the yield line, looks for conflicting traffic coming from the left, chooses an acceptable gap in the traffic flow, and then enters the roundabout with a right turn at the yield sign. Once inside the roundabout, a driver continues circling counter-clockwise until reaching the desired exit. Exit maneuvers are also right turns.

Roundabouts are pedestrian friendly. The splitter islands (see illustration above) provide a space for pedestrians in the middle of each crossing. Therefore, pedestrians only need to cross one direction of traffic at a time. The pedestrian crosswalks are set at least one full car length back from the yield line. That way, pedestrians do not have to cross in front of drivers that are looking for their gap in traffic. Experience has shown that the stopped vehicle one car length back from the yield line is more aware of pedestrians.

According to the Insurance Institute for Highway Safety, modern roundabouts reduce motor vehicle crashes. Their July 2001 Status Report noted "most serious kinds of crashes at conventional intersections are virtually eliminated by roundabouts. Crashes that do occur tend to be minor because traffic speeds are slower." The study reviewed 24 intersections around the United States that have been converted from stop signs or traffic signals to modern roundabouts. At those intersections, all crashes were reduced by 39 percent. Serious crashes were reduced by 76 percent. At the time of the study, there had been no fatalities at any of the new roundabouts. So, the study estimates that fatal or incapacitating injuries will be reduced by 90 percent at those intersections.

Modern roundabouts are usually less expensive than signalized intersections for two primary reasons:

• Expensive traffic signal equipment, as well as maintenance of that equipment, is not needed; and
• Under certain traffic conditions, the free flow movement of the roundabout is able to reduce the capacity needs of adjoining roadways; thus, fewer traffic lanes may be needed. Roundabouts usually do not require separate left- and right-turn lanes, which also helps lower costs of intersection approaches.

Since roundabouts are currently rare around the United States, all types of drivers may experience initial confusion upon their first encounter. However, as roundabouts become more common and motorists become more familiar with their operation, the initial confusion will be significantly reduced. Most people quickly learn their operation. Plus, because of the low speeds, there is generally much less risk of a crash or injury compared to a traditional intersection.

Roundabouts have design features specifically intended to accommodate trucks, buses, tractors, and larger vehicles. The main characteristic is a truck apron, a slightly raised area around the center island allowing larger trucks easier circulation in the roundabout. It is typically 3 to 4 inches higher than the paved roadway. A truck apron is used instead of increasing the normal driving width to prevent smaller vehicles from achieving higher speeds through the roundabout. With a properly designed truck apron, a roundabout is able to accommodate all types of larger vehicles.