Run-Off-Road Collisions: Appendix 4
Description of North Carolina DOT Experimental Programs with Edgeline Profile Marking and Rumble Strips for Narrow Paved Shoulders
Experimental shoulder and edgeline rumble strips for two-lane roads with no paved shoulders or narrow paved shoulders
Agency and Jurisdiction
North Carolina Department of Transportation
North Carolina DOT was experiencing excessive frequencies and rates of fatal and non-fatal run-off-road crashes on certain two-lane rural roads which did not have wide paved shoulders.
Goals and Objectives Established
To implement experimental sections of two types of rumble strips that could be used on such roads in order to study their effectiveness and operation. The ultimate goal is to reduce the rate of run-off-road collisions at such locations.
Description of Strategy(ies) Implemented
In two limited pilot programs, North Carolina has installed two innovative types of rumble strips on sections of two-lane rural roads. In the first program, they replaced standard edgeline with "profile markings" - raised/inverted thermoplastic edgeline. In the second program, milled-in rumble strips were installed on the narrow (2-foot) paved shoulder adjacent to the edgeline. The milled sections were 7-inch-wide, 5/8-inch-deep, extended 18 inches onto the shoulder, and the milled sections were separated by 5 inches of un-milled pavement. Breaks in the pattern were left at intersections.
Summary of Implementation Effort
The "profile markings" were applied on approximately 40 to 50 miles of US-64, US 264 and US 158 in eastern North Carolina. The roads are characterized by medium ADT, either unpaved shoulder or 2-foot paved shoulders, and haaving wide drainage ditches with standing water in some locations. More than one fatality had occurred when vehicles left the roadway and entered the drainage area. (North Carolina DOT also noted that some cities and towns in eastern North Carolina are asking that this treatment be used to separate travel lanes from adjacent bike/multi-use lanes in these urban areas.)
The milled-in modified rumble strips were installed in 2002 on a 9-mile section of US 601, a two-lane road in southern piedmont North Carolina characterized by medium ADT (approximately 8,000 vpd), 2-foot paved shoulders plus 3 feet of stabilized soil shoulder, limited ROW, with lots of grade changes (and thus vertical curves and limited sight distances). Unlike most North Carolina roads, this is essentially one long tangent section. The section had been characterized by high ROR rates and very high fatal crash rates.
Summary of Results
None of these treatments have been evaluated at this time. Thus, they are clearly experimental treatments.
Contact Person and Information
Kevin Lacy, Traffic Safety Systems Engineer, Traffic Engineering Branch, NC Department of Transportation, 919-733-3915.