Congestion at the main entrance to Ralston Valley High School during the school year prompted the City and the Jeffco School District to analyze the situation for possible solutions. In particular, significant queuing was occurring on eastbound W. 80th Avenue, resulting in delays at the main entrance and the student parking entrance. Motorists were observed making unsafe maneuvers such as driving on the shoulder or making U-turns to avoid the delays.
Detailed traffic counts were taken at the west and main entrances to the school as well as at W. 80th Avenue and Alkire Street. Traffic engineers concluded that a signal was warranted at the main entrance to Ralston Valley High School. While initial discussions between the City and Jeffco Schools centered on the installation of a traffic signal, City traffic engineers had reservations given that a traffic signal would be needed less than two percent of the time, and only when school is in session. Staff therefore investigated the feasibility of installing a roundabout as opposed to a traffic signal at the main entrance to Ralston Valley High School.
Roundabouts offer the following benefits:
- They eliminate left turns.
- They virtually eliminate head-on collisions.
- They slow traffic.
- They typically operate at a higher level of service than signalized intersections.
- Accidents that occur in roundabouts are sideswipe-type accidents that rarely involve injuries.
An Insurance Institute for Highway Safety study showed that fewer crashes occur at intersections with roundabouts than at intersections with stop signs or traffic signals. An analysis of 24 intersections, before and after construction of a roundabout, found a 39 percent overall decrease in crashes, a 76 percent decrease in injury-producing crashes, and a 90 percent reduction in fatal and incapacitating collisions. The Federal Highway Administration notes this important fact: traditional intersections have 32 places where travel paths can intersect and crashes can occur; roundabouts have only eight.
The City and the Jeffco School District agreed to construct a roundabout at an estimated cost of $250,000; the City share is $75,000 with the remaining cost covered by Jeffco Schools.