Use of Physical Devices for Calming Traffic along Major Roads through Small Rural Communities in Iowa

Many rural communities have developed around highways or major county roads. As a result, the main street through small rural communities is often part of a high-speed rural highway. Highways and county roads are characterized by high speeds outside the city limits and then transition into a reduced-speed section through the rural community. Consequently, drivers passing through the community may enter at high speeds and then maintain those speeds throughout. Traffic calming in small rural communities along major roadways is common in Europe, but the United States does not have experience with applying traffic calming outside of major urban areas. Seven different low-cost traffic treatments were implemented and evaluated in five rural Iowa communities. Two of the treatments physically affected the roadway cross-section. A speed table was placed along the major road (County Highway E-23) in Gilbert, Iowa, and longitudinal channelizers were used to create a center island narrowing along County Highway R-38 in Slater, Iowa. Before and after speed studies were conducted. Speed studies were conducted at 1, 3, 9, and 12 months after installation of the treatments to evaluate their effectiveness over time. Both treatments successfully reduced mean speed, 85th percentile speed, and fraction of vehicles traveling 5, 10, 15, and 20 mph over the posted speed limit; reductions were sustained over time.