Safety Evaluation of Centerline Plus Shoulder Rumble Strips

Appendix: Additional Installation Details from States

The following appendix presents additional details provided by the three participating States regarding the installation of the subject strategies in their State.

Details of the Kentucky Sites

Kentucky provided the rumble strip specifications seen in table 23:

Table 23. Installation details for Kentucky.

Kentucky was also asked to provide some additional insight on their experience with the strategy. Their responses to several topics are presented below. The following responses are provided from the perspective of the State and are phrased informally:

• Types of Rumble Strips Evaluated: All new rumble strips were milled.
  
  
• Before-Period Rumble Strip Condition: No CLRS were present, but all sites had a preexisting condition of rolled SRS.
  
  
• Retrofit or Resurfacing Projects?: Both; the retrofit sites had rolled SRS in place, and CLRS were milled in as the treatment. In the resurfacing projects, milled rumble strips were installed.
  
  
• Installation Requirements: For CLRS through resurfacing, lane widths had to be 11ft or wider and the speed limit 50 mi/h or greater. For retrofit routes, we performed visual analysis on pavement condition.
  
  
• Installation Challenges: Finding a good contractor with appropriate equipment is difficult.One contractor had a pull-behind unit on a tractor that had difficulty with maintaining the offsets and alignments.
  
  
• Installation Mechanism: Rumble strips were installed by both retrofit- and resurfacing-type projects.
  
  
• Additional Installed Countermeasures: No other safety countermeasures were installed with the rumble strips at the treatment sites.
  
  
• Lessons Learned: Do not wait for unanimous support; instead, plan your implementation and move forward.
  
  
• Maintenance Challenges: When the centerline joint starts to fail, rumbles make it look worse.However, it does not appear that it expedites the deterioration of the joint.We have not seen the CLRS joints deteriorating any quicker than the non-CLRS joints.Most challenges are overcome through information exchange and documented analysis and review of the benefits and pavement concerns.

Details of the Missouri Installations

Missouri provided the rumble strip specifications seen in table 24:

Table 24. Installation details for Missouri.

Missouri was also asked to provide some additional insight on their experience with the strategy. Their responses to several topics are presented below. As with Kentucky, the following responses are provided from the perspective of the State and are phrased informally:

• Types of Rumble Strips Evaluated: All new rumble strips were milled.
  
  
• Before-Period Rumble Strip Condition: No rumble strips. (Some locations potentially had the 30-inch wide rolled rumble strip, which is not at all aggressive.)
  
  
• Retrofit or Resurfacing Projects?: Resurfacing with paved shoulders.
  
  
• Installation Requirements: We do encourage a new pavement depth of at least 1¾ inch.
  
  
• Installation Challenges: We are now beginning to hear more from the bicycle community, but we have over 10,000 line mi now milled. As we continue to do more, we do look at the road users.
  
  
• Additional Installed Countermeasures: We did much of this effort with the combination of wider stripes (6 inches), bigger and brighter signs, and delineation (tabs at 50 ft on guardrails and cables).
  
  
• Lessons Learned: Determine a system of roadways that will benefit the most and then just do them. Yes, you need to work with your partners, but you need to develop a plan of action and go forth.
  
  
• Maintenance Challenges: Many locations have gone through several winters (freeze/thaw) and for the most part are in pretty good shape. When locations do fail, we have allowed gaps up to 200 ft to exist (in anticipation of repair).

Details of the Pennsylvania Installations

Pennsylvania provided the rumble strip specifications seen in table 25 and table 26:

Table 25. Installation details for Pennsylvania.

Table 26. Installation details for bicycle tolerable rumble strips for Pennsylvania.

Pennsylvania was also asked to provide some additional insight on their experience with the strategy. Their responses to several topics are presented below. As with Kentucky and Missouri, the following responses are provided from the perspective of the State and are phrased informally:

• Types of Rumble Strips Evaluated: All new rumble strips were milled.
  
  
• Installation Challenges: Again, minimum shoulder width needs to be installed for SRS to accommodate the bicycle community. Edgeline rumble strips should be omitted on the inside of moderate to sharp curves, which encompass dwellings. Drivers tend to use the shoulder area more in these situations, increasing the noise level. We have seen cases of pavement cracking when installing rumble strips in older pavement. We recommend only installing rumble strips where pavement is less than 3years old. (Less than 1 year is ideal pavement age.)
  
  
• Additional Installed Countermeasures: Treatment sites must have a minimum paved shoulder width of 6 ft to install SRS and 4 ft to install edgeline rumble strips. Other than paved shoulders, no other safety countermeasures were installed.
  
  
• Lessons Learned: While the combination of CLRS and SRS does create tight travel lanes for the driver, our data does not show an increase in crashes at these locations. To the best of our knowledge, there has not been any issues or complaints with this application. As long as lane width is at least 11 ft and minimum shoulder width requirements are met, we will continue to deploy this application throughout Pennsylvania. Our Roadway Departure Implementation Plan has also identified sites recommended for both CLRS and SRS.
  
  
• Maintenance Challenges: Our biggest challenge with maintenance has been rumble strips being filled in by thin overlays and not being re-installed. We have collected locations from our Districts where this is happening and information on their experiences with preserving, filling in, and re-cutting rumbles on two-lane rural highways. We are currently developing a synthesis of best practices (estimated completion June 2014) to provide guidance related to rumble strips and thin overlays.