Medians Mean Safer Streets, Researcher Finds

"Sometimes if planners give in to the demands of a small, vocal group, the general public is denied the traffic safety and convenience it deserves," said Gattis. "Planners and politicians need to communicate the improved safety and reduced congestion these designs provide."

Gattis recently conducted research projects in two mid-sized cities -- Springfield, Mo., and Muskogee, Okla. The results of his Springfield study, which confirmed the Muskogee findings, were presented recently at the Transportation Research Board's Fourth National Conference on Access Management.

Springfield is a small urban area in southwestern Missouri with a population nearing 300,000. It is home to Southwestern Missouri State University, which has over 16,000 students, as well as 10 small colleges. It is Missouri's third largest retail center.

Gattis' study of three major street segments in the same part of Springfield included traffic volume and accident data for the segments and all signalized intersecting streets. All of the street segments had four traffic lanes and same level of commercial development. One segment had an uncrossable median with few intersections spaced relatively far apart.

"The segment with the median had 20 percent fewer crashes and 20 percent fewer injuries than the other two segments," said Gattis. "In addition, traffic flow was better, with 50 percent fewer delays than on the undivided segments."

A study that Gattis conducted in Muskogee, Okla., produced similar results. The street with a high level of access management -- an uncrossable median with a limited number of driveways -- was both safer and had fewer delays to motorists.

Traffic engineers have known about this for decades, according to Gattis. Although it was recommended practice in the National Urban Street Design Manual in the 1950s, it has largely been ignored until recently. This is because conflicting demands from the public frequently cause problems for city and state street planners.

"Now some states, such as Missouri and Kansas, as well as some cities, are developing programs to implement high-level access management on a larger scale," Gattis explained. "Basically it comes down to how much the government entity is committed to traffic safety and avoiding congestion. Will they listen to expertise in the field or just repeat the errors of the past?"