Iowa Department of Transportation
Shauna Hallmarkshallmar@iastate.edu email >
Theresa Litterallitteral@iastate.edu email >
Statewide MDST Facilitator, Iowa LTAP
About the research
About 56% of traffic fatalities in the US are due to roadway departures. One strategy to address roadway departures is the use of a 6-inch versus 4-inch edge line. Use of the wider edge line is expected to increase conspicuity of the edge line, particularly in wet conditions. Additionally, the extra material may slow marking degradation due to increased surface cover making the edge line visible for a longer period of time.
Several CMFs for wider edge lines were available through the Crash Modification Factor (CMF) Clearinghouse. CMFs ranged from 0.53 to 0.96 depending on crash type. However, the CMFs were derived from a single study in Texas.
The cost of installation is expected to be around 33% over the cost of regular edge lines. As a result, additional information on the effectiveness of wider edgelines would be helpful to assist agencies in programming safety funds.