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Conclusions The authors examined four strategies for designing subdivision streets without road humps. Narrower streets result in lower travel speeds and also cost less to construct and allow larger building lots. Although 29-foot streets were found to be acceptable, the 32-foot streets section resulted in similar travel speeds and had much greater acceptance by emergency services providers, the builders and drivers. Street alignment was also found to affect driver behavior. In general, the straighter the road, the higher the speed. However, curves as gentle as a 350-foot radius were enough to reduce both the average speed, mostly through the elimination of travel speeds more than 10 MPH over the posted speed limit. The most effective method is more curves with shorter radii. Traffic chokers and median islands are both effective. The median islands are more difficult to design but they add unique design features and can help to support other subdivision amenities. Maintenance of the islands has not proven to be much of an issue although even a small island can cost $2,000 to construct and reduces the adjacent lot sizes.. Curbside traffic chokers are also effective. However, they must be located away from intersections to minimize their impact upon the larger vehicles. The midblock locations do nothing to minimize their effectiveness. Unlike the median islands, there are no special maintenance issues with the traffic chokers. Chokers have an insignificant cost if designed into a new subdivision and have no impact upon the adjacent lot sizes. Retrofitting chokers into an existing subdivision can cost up to $2,500 per location Block lengths were also examined with the belief that more frequent intersections increase driver expectation and result in lower speeds. Residential streets cost approximately $100 per linear foot for construction. Each new street may also remove to potential buildable lots. Although there is no direct cost to the jurisdiction, these costs are typically passed into the costs of the remaining subdivision lots. REFERENCES 2. 3. 4. 4 5 6 Institute of Transportation Engineers. Traffic Engineering for Neotraditional Neighborhoods. ITE Education Foundation Seminar. Washington, D.C. 1995. Swift and Associates. Residential Street Typology and Injury Accident Frequency. 1997. Transportation Research Board Special Report 209. Highway Capacity Manual, 1995. Institute of Transportation Engineers. DRAFT Traffic Engineering for Neotraditional Neighborhoods. ITE Technical Committee P.-8. Washington, D.C. 1992. Szplett, David, and Larry Sale. An Acceptable Neotraditional Neighborhood Design. ITE Journal. (July. 1997): 42-48. Szplett, David, and David Butzier. "Design Guidelines for Transportation Elements of Neotraditional Neighborhoods." Institute of Transportation Engineers' 1998 Annual Meeting Compendium of Technical papers. Ada County (Idaho) Highway District. Development Policy Manual. Boise, Idaho. 1996.