More than 20 percent of fatalities nationwide occur at intersections and more than 80 percent of rural intersection fatalities are at unsignalized intersections.
In Iowa, intersection crashes account for 30 percent of severe crashes, with 40 percent of those crashes occurring in rural areas (Iowa DOT 2013).
A list of general resources developed in Iowa to reduce rural intersection crashes is found here.
A summary of known performance for each rural intersection countermeasure is provided in the table below.
|Rural Intersection Countermeasures||Speed Impact (mph)||CMF1||Other Crash Impacts1||Cost2||Usage Within Iowa||Iowa-Specific Guidance|
|increase visibility of stop signs|
|higher retroreflectivity||N/A||N/A||-1 to -38%
|$||common||refer to MUTCD|
|double stop signs||N/A||N/A||-11 total
-55% right angle
|$||???||refer to MUTCD|
|larger stop signs||N/A||N/A||-19%||$||???||refer to MUTCD|
|adding retroreflective material to stop sign||N/A||N/A||-100%||$||???||refer to MUTCD|
|LEDs in sign face||-2.7%||N/A||-42% in right angle||$$||???||refer to MUTCD|
|channelization (info is primarily from signalized intersections)|
|left turn lanes||N/A||0.66 to 0.93||-18 to -44%||$$$||???||refer to MUTCD or Iowa Design Manual|
|right turn lanes||N/A||0.85 to 0.96||-18 to -27%||$$$||refer to MUTCD or Iowa Design Manual|
|advance stop line rumble strips||-5||1.11 to 1.22
0.41 to 0.65 fatal/major injury
|-43%||$$||common||Iowa DOT Design Manual, Chapter 6, 6A-7; Iowa DOT Traffic and Safety Manual, Chapter 18|
|standard overhead||N/A||N/A||-12 to -39%
-12 to -19% angle
-40% severe injury
-26% ran-stop sign
|$$||limited||refer to MUTCD|
|stop sign mounted||N/A||N/A||-40%
|$$||refer to MUTCD|
|lighting||N/A||N/A||0 to -49%||$$$||occasional||Iowa DOT Traffic and Safety Manual, Chapter 6; Iowa Statewide Urban Design Standards, Chapter 11|
(1) Actual crash reductions and CMF will vary by crash type. CMF and crash reduction values which were determined to be the most appropriate for Iowa rural two-lane roadways were selected from a range of studies.
(2) Estimated installation costs ($ < $5,000; $$ $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.
Golembiewski, G.A. and B. Chandler. Intersection Safety: A Manual for Local Rural Road \ Owners. Report FHWA-SA-11-08. Federal Highway Administration, Office of Safety, 2011. http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.
Iowa DOT. Iowa Strategic Highway Safety Plan: July 1, 2013–December 31, 2016. Iowa Department of Transportation, 2013. http://www.iowadot.gov/traffic/shsp/pdf/SHSP.pdf.
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