Keeping the Rumble in the Strips
Maintenance crews were initially concerned that heavy traffic would cause shoulder pavements with rumble strips to crumble faster, or that the freeze-thaw cycle of water collecting in the grooves would crack the pavement. These worries have proved to be unfounded.
There appears to be little early deterioration of milled shoulder rumble strips on either cement concrete or asphalt pavements from either source. Rumble strips have little effect on the rate of deterioration of new pavements. Older pavement shoulders tend to degrade more quickly, but tests in several States show that these rumble strips continue to perform their original function—making noise and creating vehicle vibration. There are also no apparent problems with installation or faster deterioration of rumble strips on open-graded pavements. Road agencies do advise against installing rumble strips on pavements that are rated as deformed or that show high degrees of deformation and/or cracking distress. Consult the Pavement Rehabilitation Manual.
Weather also appears to play no significant role in the durability of shoulder rumble strips. Field tests refute concerns about the effects of the freeze-thaw cycle as water collects in the grooves. These tests show that vibration and the action of wheels passing over the rumble strips in fact knock debris, ice, and water out of the grooves. Ironically, snow plow drivers have come to depend on shoulder rumble strips to help them find the edge of the travel lane during heavy snow and other low visibility situations. In mountainous areas, shoulder rumble strips are handy because they provide tread for vehicles traveling up long slopes.
Weather does play havoc with raised rumble strips. Snow plow blades passing over the rumble strips tend to scrape them off the road surface. Which is, of course, why this type of rumble strip is usually restricted to use in areas that don't contend with snow removal.
Shoulder rumble strips also challenge maintenance and rehabilitation crews when lane closures require traffic to be diverted to the shoulder. For long-term rehabilitation projects on asphalt pavements, most road agencies simply fill in the rumble strips by milling a trench along the shoulder of the rumble strip and filling the trench with asphalt. Once construction is complete, the shoulder is resurfaced and new rumble strips are milled into the new asphalt overlay.
If you are interested, you may also follow an “off-line” discussion by several State and Federal highway engineers from around the US addressing concerns about possible adverse effects on asphalt shoulder pavement quality, snow plowing operations and large truck/trailer operations on rural freeways due to the presence of shoulder rumble strips.
Roadside Design: Steel Strong Post W-beam. A guidance memo was issued on May 17, 2010 on the height of guardrail for new installations. Guidance regarding existing guardrail will be developed in the next several months, in consultation with AASHTO’s Technical Committee on Roadside Safety.