Nationally, speeding is a contributing factor in 31 percent of fatal crashes.
Nationally, speeding is a contributing factor in 31 percent of fatal crashes (NHTSA 2008).
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, which then transition into a reduced speed section through the rural community. Consequently, drivers passing through the community often enter at high speeds and maintain those speeds as they travel through the community. Traffic calming in small rural communities along major roadways is common in Europe, but the US does not have experience with applying traffic-calming measures outside of major urban areas.
Speeding in rural areas is particularly problematic since rural agencies and communities lack the resources for regular enforcement while the remoteness of much of the system makes timely emergency response difficult.
A list of general resources developed in Iowa to address speed management in rural communities is found here.
A summary of known performance for each speed reduction countermeasure is provided in the table below.
|Speed Reduction Countermeasures||Highest Speed Impact (mph)||CMF1||Other Crash Impacts1||Cost2||Usage Within Iowa|
|horizontal physical displacement|
|bulb-outs, neck-downs, chokers, or mid-block crossings||-2.60||$$$||occasional|
|chicanes or serpentines||-6.20||$$$||no experience|
|roundabouts||0.27 to 0.58||$$$||occasional|
|transverse rumble strips||0.64 to 0.66||$$||not tested|
|vertical physical displacement|
|raised intersections||1.05||not tested|
|speed humps and tables||-10.0||$$$||occasional|
|speed lumps, slots, and cushions||-9.0||not tested|
|center islands||0.29 to 0.61||$$||common|
|vertical centerline treatments||-3.0||$||tested|
|shoulder widening to narrow travel lanes||-0.00||$$||tested|
|four- to three-lane conversions||-5.0||0.47 to 0.63||widespread|
|transverse lane markings||-5.0||$$||tested|
|pavement marking legends||0.00||$$||tested|
|wide edge lines||0.57 to 1.05||$$||no experience|
|traffic control signs|
|radar-actuated dynamic message display sign||-7.00||$$$||tested|
|radar-actuated LED sign||-7.00||$$$||tested|
(1) Actual crash reductions and CMF will vary by crash type. CMF and crash reduction values which were determined to be the most appropriate for Iowa rural two-lane roadways were selected from a range of studies.
(2) Estimated installation costs ($ < $5,000; $$ $5,000 to $10,000; $$$ >$10,000) — actual cost depends on size of treatment location, actual product selected, whether treatment is done in conjunction with other activities such as resurfacing/paving, etc. Maintenance costs can vary considerably but are not estimated.
NHTSA. Traffic Safety Facts 2007 Data: Speeding. DOT HS 810 998. National Center for Statistics and Analysis, National Highway Traffic Safety Association, 2008.
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