Impact of Non-Freeway Rumble Strips Gregory C. Johnson, PE Chief Operations Officer Michigan Department of Transportation (5 minutes) When you drive your car over a Michigan Highway center line you will feel and hear the vibrating wake up call of a rumble strip to bring your car back into your lane. We call that the sound of another life being saved. I had the privilege of serving on the research advisory panel that studied these life saving rumble strips.

Introduction Michigan Department of Transportation Project Manager: Jill Morena, PE Wayne State University: Timothy J. Gates, PhD, PE Peter T. Savolainen, PhD, PE Tapan K. Datta, PhD, PE Ryan G. Todd Brendan J. Russo tjgates@wayne.edu The project was managed by our pavement marking engineer Jill Morena. The contracted research team that conducted the research included three professors from Wayne State University and several hard working students that viewed over 700 hours of video, rode bicycles around rumble strips, and counted cracks along about 5,000 miles of road.

Problem Statement Reduce Lane-Departure Crashes Rumble Strip Installation 5,400 Miles of Non-Freeway Centerlines Shoulders Evaluate Rumble Strip Installations and Provide Future Implementation Guidance Driving out of your lane in rural Michigan is one of the leading causes of crashes and probably in many of your states accounts for a large percentage of fatal crashes. In Michigan this type of crash accounted for. 20% of all crashes 61% of fatal crashes (the largest percentage) In an effort to reduce lane-departure crashes, in 2008 the Michigan Department of Transportation (MDOT) began a three-year statewide non-freeway rumble strip installation initiative. This initiative called for the installation of milled centerline rumble strips on all rural non-freeway highways with a posted speed limit of 55 mph a paved roadway width greater than 20 ft and shoulder rumble strips on roadways with paved shoulders that were at least 6 ft wide. Approximately 5,400 miles of non-freeway roadways were ultimately included in this rumble strip installation initiative. As this initiative is believed to be the largest of its kind in the United States at its time, it was important to evaluate the impacts associated with the rumble strip installations and provide guidance for future implementation.

Research Performed Video of Driver Behavior Encroachment Centerline Shoulder Passing Maneuvers Bicyclists Vehicles Surveyed Bicyclists about Rumble Strips We used pole-mounted high definition cameras to collect video data of driver behavior both before and after the installation of centerline rumble strips. After the 700 hours of manual video review, data shows: how well vehicles were centered within their lanes; the reduction in corner cutting effects on passing maneuvers. Including the lateral displacement of drivers when passing bicyclists. Additionally, we surveyed Michigan bicyclists about the effect of rumble strips on their safety and comfort.

Research Performed Crash Data Analysis Video Logs of Pavement Centerlines Evaluate Pavement Cracking Before and after Rumble Strip Installations Roadside Noise We also: • Developed a comprehensive database of crash data before centerline rumble strip installation to establish a baseline for later comparison to crash data after installation. Total target crash and injury frequency decreased considerably during the “After” period. Injury crashes are substantively lower in the “After” period • Used MDOT’s pavement management system video logs to evaluate 5,000 miles of pavement counting cracks before and after centerline rumble strip installations. • Set up ambient noise detectors and evaluated roadside noise due to installations. 2008 installation Before Crashes After Crashes 1,494 miles 584 392

Results Safety Pavement Performance Noise Improved Driver Performance Do not Contribute to Short-Term Transverse Cracking in Asphalt Pavements Noise Deeper Rumbles Produce Higher Noise Levels Noise Typically did not Exceed the Roadside Noise Level Produced by Tractor-Trailer Safety Researchers found that the presence of centerline rumble strips on rural high-speed non-freeway highways improves driver performance in most conditions. Drivers position themselves more centrally in lanes, leading to fewer encroachments over centerlines and shoulders, thus increasing safety. More bicyclists felt safer with rumble strips placed on 6 foot shoulders and than with rumble strips placed on narrower shoulders.   Pavement performance: Centerline rumble strips did not contribute to short-term transverse cracking in asphalt pavements. Noise: The noise from rumble strips was incrementally higher for rumbles strips with a depths greater than ½ inch. leading us to limit their depth. Vehicles produced higher levels of roadside noise when traveling over rumble strips than they did traveling over regular pavement, but this noise typically did not exceed the roadside noise level produced by tractor-trailer trucks traveling on normal highways.

Recommendations Depth of 0.5 Inch at the Center and 0.375 Inch at the Outer Edges Reduces Noise Installation on 6 Foot or Wider Shoulders Increases Bicyclist Perceived Safety Overall the recommended installation of rumble strips was upheld by this research, but I’d like to highlight 2 specific recommendations and commend the summary spotlight document or full report to your reading: First how deep should they be to minimize ambient noise and still be effective? ½ inch at the center line Second how wide should the paved roadway shoulders be before they are installed? 6 feet These are specifications that lead to improved quality of life with lower noise levels and safer roads for bicycles. You can access the report or summary spotlight at our MDOT research website. Copies of the spotlight are available here for your use. Report Available @ www.michigan.gov/mdotresearch

Implementation Status and Strategy Installing Rumble Strips Follow Specification Communicate Results Research Spotlight Three TRB Papers Phase II Project Quantify the Benefit Develop Guidelines Cities Counties “We expect Phase 2 of this project to give transportation agencies in Michigan and other states the data they need to implement their own initiatives.” Jill Morena, PE Project Manager What are we doing about all this good information? We are installing them and following the specification We are communicating the information Every project with exciting findings like this one we develop a spotlight summary to get research results to a broad audience We have had three papers presented at TRB on this one topic to share the findings of this research We have embarked on a second phase of this research to quantify the life saving crash reducing benefit of rumble strip installations And Develop a how to install rumble strips document to help cities and counties through out Michigan install rumble strips on their roadways. MDOT only has jurisdiction over 8% of its roads leaving over 600 local agencies to implement similar systems on their roads.

Value Save Lives and Reduce Crashes Annually 60 Incapacitating Injuries 15 Lives Improving the Quality of Life Investment Research $262,829 Construction 3 years @ $2.7M /year Total $8.3 Million We know people get distracted — we know people get tired — we never know where people are going to do this - we did not want to wait until someone has a crashed. We made a $8.3 million investment. It works out to about 28 cents a foot, that’s an incredible investment for the return you get with lives saved Based on the literature, we project a reduction of more than 300 crashes annually a reduction of approximately 60 incapacitating injuries annually and 15 lives saved annually

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