Guidance for the Design and Application of Shoulder and Centerline Rumble Strips (2009)

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Appendix C Detailed Summary of Survey Results

C-1 This appendix provides a detailed summary of the survey responses received from 27 U.S. state transportation agencies and 4 Canadian provincial transportation agencies. Responses to categorical questions are summarized by showing both the percentage of the responses and the frequency/number of responses shown in parentheses. For those questions that asked agencies to further explain an issue, the explanations are provided in bullet form. Survey Results: Shoulder Rumble Strip Policies and Practices 1. Does your agency have a written policy concerning the installation/application of shoulder rumble strips? YES: 80.6% (25) NO: 19.4% (6) If no, does your agency use shoulder rumble strips? YES: 16.1% (5) NO: 3.2% (1) Total agencies using shoulder rumble strips: 96.8% (30) States/Provinces that have their policy information available on the internet: Arizona, Iowa, Indiana, Minnesota, North Carolina, North Dakota, Nevada, Oregon, Pennsylvania, Texas, Utah, Virginia, Washington, British Columbia. 2. On what types of roadways does your agency install shoulder rumble strips? Urban freeways: 54.8% (17) Urban freeway on-ramps and off-ramps: 9.7% (3) Urban multilane divided highways (nonfreeways): 32.3% (10) Urban multilane undivided highways (nonfreeways): 22.6% (7) Urban two-lane roads: 12.9% (4) Rural freeways: 96.8% (30) Rural freeway on-ramps and off-ramps: 22.6% (7) Rural multilane divided highways (nonfreeways): 77.4% (24) Rural multilane undivided highways (nonfreeways): 71.0% (22) Rural two-lane roads: 71.0% (22) Other: 3.2% (1) 3. On roadways with medians, does your agency install shoulder rumble strips on both the right (outside) and left (median) shoulder? YES: 93.5% (29) NO: 6.5% (2)

C-2 If yes, does your policy differ between rumble strips installed on the right (outside) versus the left (median) shoulder? YES: 35.5% (11) NO: 51.6% (16) If your policy differs, what are the primary differences? • For instance, the right strips are located 2 ft from the edge of the traveled lane, but the left strips are located 1 ft from edge of travel lane. For multilane divided, the right strips are intermittent (40-ft milled strip with a 10-ft gap), but the left stripes are continuously milled. • We use a 4-in offset from the high speed lane (left edge lane), and a 12-in offset from the low speed lane (right edge lane). • Where left (median) shoulder is narrower than outside (4 ft vs. 10 ft), strips are milled 6 in from pavement edge vs. 30 in. • We require wider shoulders on the right to install rumble strips in response to the bike community. • As a general rule we do not install shoulder rumble strips on both sides of the road, however, in the case of a two-lane road being converted to one direction of a divided highway there can end up being rumble strips on both shoulders. • On a freeway, the strips are continuous on both shoulders of each roadway. On a nonfreeway, the strips are intermittent on the right or outside, and continuous on the left or inside. • For multi-lane roadways (Interstate), rumble strips are continuous on the inside (left median) shoulder strips and have gaps on the right shoulder. • Median rumble strips are continuous vs. outside rumble strips are intermittent on non- Interstate/freeways. • The offset on the left (median) shoulder is 6 in, and the offset on the right (outside) shoulder is 1 ft. • Periodic Gaps (10-ft gap, 40-ft cycle) in right shoulder, continuous in left shoulder. 4. Does your policy concerning shoulder rumble strips differ depending upon the type of shoulder surface? YES: 38.7% (12) NO: 54.8% (17) If yes, please elaborate: • Rumble strips are only used on PCC and asphalt surfaced shoulders. They are not used on sealed shoulders. • Only concerning rumble strip construction. • Rumble strips are not allowed on pavement joints (concrete pavements). • Standards for placement on concrete shoulders differ slightly from placement on asphalt shoulders.

C-3 • We only use them on asphalt shoulders. • Only in that they shall be installed on shoulders with a projected service life of less than three years. • On asphalt it may require a flush coat. • Although we did this in a few locations in the past, our current policy says do not install rumble strips in cement concrete pavement. • Although our policy states that shoulder rumble strips can be constructed on either asphalt or concrete shoulders, our agency is not milling in rumble strips into concrete. On two freeway contracts in 2004 involving construction of new concrete pavement, since our agency overbuilds the outside driving lane by 1.6 ft into the shoulder (i.e., shoulder is 1.6 ft concrete and 8.2 ft asphalt), the rumble strips have been shifted outward 2 ft from the travel way into the asphalt. There were concerns about rumble strips potentially causing micro-cracking in the concrete which could affect pavement durability. There is also concern about installing rumble strips in open friction coarse (OFC) pavement, as noted in our policy. • In some cases the shoulder texture is rough and acts as a rumble strip without installing any. Usually this roughness is from a fillet that is formed as part of milling and filling the driving lanes on pavement surface rehabilitation projects. 5. How close to the edgeline does your agency install shoulder rumble strips? Responses range from flush against the edgeline (i.e., 0 in) to 30 in from the edgeline. If the lateral placement from the edgeline is variable, what specific features are considered in determining the lateral placement of the shoulder rumble strips? • Some districts place them farther than 6 in to keep the wheels of the snow plow off of the rumble strip when plowing the shoulder. • The standard offset from the paint line is 4 in, except when 0 in is used in order to get at least 4 ft shoulder width free of the strip for bicyclists. • Where left (median) shoulder is narrower than outside (4 ft vs. 10 ft), strips are milled 6 in from pavement edge vs. 30 in. • Whether the shoulder is on the right/shoulder or left/median side. • Total width of outside paved shoulder determines lateral placement. Lateral set-back is 8 in with shoulder widths of 4 ft to less then 6.5 ft. Shoulder widths equal to or greater then 6.5 ft have 1-ft lateral clearance. • Offset can vary slightly if necessary to avoid deteriorated pavement at lane/shoulder interface. 6. At what specific features or areas along the shoulder/roadway (e.g., ramps or catch basins) are rumble strips discontinued to avoid adverse consequences (e.g., pavement deterioration, noise, etc)? • Rumble strips along main lines are interrupted at entrance and exit ramps. • Discontinued at ramps, in suburban/urban areas, and where clear shoulder width drops below 3.5 ft.

C-4 • At turn and auxiliary lanes road approaches, residences, 250 ft before intersections, and anywhere else as directed by the project engineer. • For catch basins, the rumble strips must be placed 2 ft from the basin or else the rumble strips must be discontinued. The rumble strips should be placed at least a foot from longitudinal paving joints. Also, the rumble strips are discontinued at the beginning of the tapers for off-ramps, continued in between the off and on ramp and then discontinued for the on-ramp, and then continued at the end of the taper of the on-ramp. • Ramps, intersections, bicycle considerations, structures and approach slabs. • Guardrail adjacent to shoulder, public road approach, driveway. • We gap entrances, mail box turnouts, and median crossings. • Shoulder rumble strips are omitted between the radius points for side road approaches, entrances and median crossovers. Shoulder rumble strips should be omitted on bridges and on ramps for diamond, single point, partial cloverleaf and similar types of interchanges, but may be considered on longer ramps for directional or other large interchanges. • Ramp terminals, intersections, loop terminals, catch basins, and bridges. • Exit/entrance ramps, turning lanes, intersections, approaches/private drives, and scenic/historical marker turnouts. Shoulder rumble strips are not installed within urban areas, where there is curb and gutter, where the posted speed limit is 45 mph or less, across bridge approaches /decks, or adjacent to guardrail if the clear path between shoulder rumble strip and guardrail is <5 ft. • Bridge decks; where the distance between the fog line and obstructions such as barrier or guardrail is 4 ft or less; in snow zones, climbing areas, or rolling mountainous terrain; in sections with horizontal curvature except where the data indicates a significant single vehicle run off the road problem; in the area between 300 ft before the exit ramp and 330 ft after the last entrance as measured from the point where the fog stripe departs and rejoins the mainline. • SRS are discontinued at the following locations: Intersections, accesses, ramp terminals, where the outside shoulder is less than 5 ft, on bridge decks, at drainage gates when the shoulder width is less than 6 ft. • Shoulder rumble strips are interrupted at intersections with side roads and farm accesses. 7. What features directly affect installation requirements within your agency’s shoulder rumble strip policy or guidelines? Roadway Type: 74.2 % (23) Shoulder Width: 80.6% (25) Lateral Clearance: 41.9% (13) ADT: 29.4% (6) Bicycles: 54.8% (17) Pavement Type: 35.5% (11) Pavement Depth: 25.8% (8) Area Type (i.e., urban vs. rural): 58.1% (18) Speed Limit: 16.1% (5) Crash frequency/rate: 35.5% (11) Other: (5; listed)

C-5 • Single vehicle off-road to the right crash frequency. • Condition of existing shoulder. • Scheduled upgrades for the facility. • For concrete pavements, at discretion of Traffic Engineer as to continuous rumble strip or structural rumble strip every panel (about 15 ft) • The presence of run off the road accident patterns. 8. Does your agency have a minimum shoulder width requirement for the installation of shoulder rumble strips? YES: 61.3% (19) NO: 35.5% (11) If YES, please elaborate: Response answers ranged from 2 ft to 6 ft. 9. Does your agency have a minimum lateral clearance requirement for the installation of shoulder rumble strips? YES: 45.2% (14) NO: 51.6% (16) 10. Does your agency have a minimum traffic volume requirement for the installation of shoulder rumble strips? YES: 16.1% (5) NO: 83.9% (26) If YES, please elaborate: • Rumble strips are installed when AADT is greater than 1800 veh/day. • For state corridor highways with shoulder widths of 4 ft or greater and the ADT is 2000 veh/day or greater, rumble strips should be installed. However, even if this criteria is not met they may be installed based on crash history. • Our paved shoulder policy states an ADT of 3000 veh/day before we pave shoulders so that is the de facto number for rumble strips. • Two-lane rural greater then 50 mph and ADT of 400 veh/day should have rumble strips. 11. Does your agency have a minimum pavement depth requirement for the installation of shoulder rumble strips? YES: 25.8% (8) NO: 74.2% (23)

C-6 12. Does your agency have a minimum speed limit requirement for the installation of shoulder rumble strips? YES: 12.9% (4) NO: 83.9% (26) If YES, please elaborate: Minimum speeds ranged from 45 to 50 mph. 13. Does your agency have a minimum crash frequency/rate requirement for the installation of shoulder rumble strips? YES: 6.5% (2) NO: 90.3% (28) If YES, please elaborate: • In locations with higher numbers of run-off-road crashes, minimum shoulder width requirements can be waived if justified by a study. • Type of accident and frequency is compared to statewide average. • For undivided highways we specify 0.6 crashes per mi or 34 crashes per 100 million VMT; however, we state that these number are not to be used as absolute values. We provide the values to establish a “baseline” for high accident experience. The numbers come from a system-wide analysis of run off the road crashes. 14. Does your agency’s policy change depending upon whether shoulder rumble strips will be installed along a designated bicycle route? YES: 38.7% (12) NO: 58.1% (18) If YES, please elaborate: • Our policy states rumble strips can be omitted on highways "with significant bicycle traffic.” • Shoulder rumble strips have not been installed in areas of high bicycle use, but not specifically because of a bicycle route designation. • Strips are not placed along a designated bicycle route. • The rumble strips don't change but the shoulder policy does. Our stand is a 4 ft paved shoulder with 6-ft granular shoulder outside of that. On a designated bicycle route that changes to 6-ft paved but the rumble strip placement and pattern remain the same. • Shoulder widths of 4 ft (1.2 m) or less with rumble strips will not adequately accommodate bicycles. Therefore, rumble strips should not be placed on these roadway sections unless the District Traffic Engineer has documented a serious ROR accident problem and little or no bicycle traffic is expected. Districts shall contact the State Bicycle Coordinator to determine the amount of bicycle traffic on a roadway. • This is on a case by case basis but typically if there is significant bicycle traffic, milled rumble strips would not be installed on shoulders less than 8 ft wide.

C-7 • Modifications are made to the standard RS that better accommodate bicycle transportation on designated bicycle routes or facilities where the engineer has determined that significant bicycle travel exists for at least several months of the year. Essentially the revised guides provide 6-ft center to center gaps and a continuous 34-ft milled rumble on a 40-ft cycle. • Strips are installed on limited access highways where bicycles are not allowed. • Pattern selection changes depending on bicycle usage. Our policy includes consultation with the Washington Bicycle and Pedestrian Advisory Committee. • Shoulder rumble strips should not be installed on highways with partially paved shoulders (2-ft asphalt width) that are designated as bicycle routes or have substantial volumes of bicycle traffic. • Shoulder rumble strips are usually installed on a continuous basis. On designated bicycle routes we will provide an intermittent 13-ft gap between rumble strips. 15. Does your agency’s policy provide a gap in the shoulder rumble strip pattern to allow bicyclists to maneuver from the travel lane to the shoulder and back without traversing the rumble strips? YES: 35.5% (11) NO: 54.8% (17) If YES, please describe the gap pattern and whether it varies with the type of facility: • Right shoulder on noncontrolled-access highways—10-ft gap on 40-ft cycle roughly even with roadway striping. • 28-ft ground-in rumble strips and 12-ft gap typical unless interstate/freeway which is continuous. • In areas where bicycle traffic is anticipated to cross-over rumble strips the installation of a 6-ft to 12-ft gap in the strips is recommended. • 48 ft of rumble strips, 12 ft of gap. • Gap provided only when justified. Gap pattern does not vary with facility type. • For multilane divided highways, multilane undivided highways and 2 lane highways (paved shoulders equal or greater than 6 ft) there a 40-ft milled strips with 10-ft gaps on the right shoulder. • We have three different patterns that allow a balance to reflect shoulder width, truck usage, and bicycle usage. We have two 12-in wide patterns, one with a 12-ft gap and 48-ft of continuous rumble strip, one with 12-ft gap and 28 ft of continuous rumble strip. We have a 16-in wide pattern with a 16-ft gap and 48-ft of continuous rumble strip. • The gap is 12-ft followed by a 50 ft of strip. Note that we may be reviewing the length of the gap in the near future. • Gap pattern is four meters of rumble strip followed by four meters of pavement. It does not vary with facility type. 16. Most agencies that use shoulder rumble strips install them continuously along extended sections of roadway. Does your agency, in some cases, install shoulder rumble strips along specific shorter sections of roadway (e.g., specific horizontal curves)?

C-8 YES: 29.0% (9) NO: 71.0% (22) If YES, please elaborate: • Where a pattern of run-off-the-road accidents are present. • If there is a significant number of single-vehicle run-off-the-road accidents rumble strips are considered for installation in these areas. • Horizontal curves. • If crash history would indicate this strategy is appropriate. • Shorter sections can be utilized at the discretion of the engineer. This is also done in some instances where centerline RS are used in curve sections. • Although rare, we do occasionally apply shoulder rumble strips to reduce cutting the corner by driving on the shoulder. In one instance we had drivers approaching an intersection on the inside of a curve, by driving on the shoulder. This created conflict when drivers waiting at the side street crowded the stop bar. In another instance, we had a mountainous road with a rock cut along the shoulder. There were occurrences where drivers on the shoulder were encountering rocks that had fallen on the shoulder. • Our agency installs rumble strips at two-lane to four-lane transitions, bridge approaches, and on the top of curves at high accident areas. 17. Has your agency installed milled, rolled, or formed rumble strips directly on the edgeline of the traveled way? YES: 48.4% (15) NO: 51.6% (16) 18. Has your agency installed textured pavement edgeline markings (e.g., thermoplastic) to stimulate the driver with audible or tactile sensations (i.e., rumble stripes)? YES: 29.0% (9) NO: 71.0% (22) If YES, please elaborate: • These have been utilized on a limited basis in the past, but use is being phased out. These markings (Pavement Profile Markings) are very expensive, and there are maintenance issues associated with their use. • We use profiled thermoplastic pavement markings on some roadways. No criteria design choice or preference. • We installed Vibraline edgelines (thermal plastic) along the 3 mi of SR 900. • These are effective to alert drivers, but we don’t think that these are a substitute to SRS. They may not be loud enough to stimulate a driver who is on the verge to dosing. 19. Has your agency’s policy/practice of installing shoulder rumble strips changed recently (i.e., within the last 3 to 5 years)?

C-9 YES: 48.4% (15) NO: 51.6% (16) If YES, how has it changed? • Developed policy to install intermittent rumble strips and shoulder width less then 6-ft width. • Most major installations of rumble strips along long roadway sections has occurred within the last 5 years. • We install milled strips only. We have discontinued use of rolled or formed strips. • We used to roll them in and now we mill. • Milled strips on interstate and parkways (freeways). • Policy was revised October 2004 to allow more wide spread and flexible utilization of continuous rumble strips. • In January 2005, the RIDOT guidelines for shoulder rumble strips were first established. Before this, rumble strips were simply installed on a case-by-case basis. • We introduced the intermittent gaps, modified the discontinuations at intersection and obstacles and reduced the shy distance to the paint line to 0 in in some cases and reduced the SRS length from 16 in to 12 in. • If yes, why has it changed? • Accommodate bicyclist and to address narrow shoulders respectively. • Recognition that rumble strips are a cost effective means of reducing single vehicle run- off-the-road accidents. • Rolled or formed strips may only on newly placed pavement. Milled strips may be placed on any pavement, regardless of age. We have also determined that rolled strips are quieter, therefore less effective, than milled strips. • Better info available about performance. Also, we are paving more shoulders now where before they were granular. • Providing high standards to these roadways. • To allow more wide spread use of rumble strips as an effective countermeasure for lane departure type crashes, and to improve positive guidance. • It was determined desirable to formally establish RIDOT’s guidelines. • Mainly to accommodate the bicycling community requests. 20. Do you anticipate that your agency’s policy/practice of installing shoulder rumble strips will change in the next year or so (i.e., are changes planned or are modifications currently being drafted)? YES: 29.0% (9) NO: 71.0% (22) If YES, please explain what type of modifications will be made or are anticipated?

C-10 • Development of a policy for the installation of rumble strips. No policy currently exists. Also, issues related to noise impacts will be investigated. • We are in the process of developing a policy for non-Interstate roadways. • Our new design philosophy will be looking at all standards and their cost vs. safety. • Current typical details and specifications are DRAFT only. • We may allow more uses on 2 lane undivided roadways with shoulders. • May review the length of the intermittent gap between the strips. • Consideration is being given to modifying the variable depth standard to a constant 0.5 in depth and painting wider edgelines through them to improve retro-reflectivity. Trial expected to start later this fall. If YES, what is the basis or justification for the planned changes? • There have been several roadways with safety problems where shoulder rumble strips would be beneficial, but not installed due to noise concerns. • We desire to have typical details and specifications to achieve consistency in installations. • Results from TTI research. • We want to make sure that these gaps are sufficiently long to allow cyclists to weave across while at the same time ensure that drivers who wander across the SRS will be properly alerted by the vibrations. • Improved edgeline retro-reflectivity under wet conditions. Survey Results: Centerline Rumble Strip Policies and Practices 21. Does your agency have a written policy or set of guidelines for the installation/application of centerline rumble strips on undivided roads? YES: 29.0% (9) NO: 71.0% (22) If NO, does your agency use centerline rumble strips? YES: 45.2% (14) NO: 25.8% (8) Total agencies using centerline rumble strips: 74.2% (23) 22. Concerning the lateral placement of centerline rumble strips, check the type(s) of applications that have been installed by your agency?

C-11 Centerline rumble strips within pavement markings: 38.7% (12) Centerline rumble strips extend into travel lane: 48.4% (15) Centerline rumble strips on either side of pavement markings: 6.5% (2) 23. On what type of roadways does your agency install centerline rumble strips? (Select all that apply) Urban multilane undivided highways (nonfreeways): 9.7% (3) Urban two-lane roads: 6.5% (2) Rural multilane undivided highways (nonfreeways): 38.7% (12) Rural two-lane roads: 71.0% (22) Other: 6.5% (2) 24. Does your agency have a minimum lane width requirement for the installation of centerline rumble strips? YES: 9.7% (3) NO: 71.0% (22) If YES, please elaborate: • We specify 12 ft as the minimum width (combined lane and shoulder) for centerline rumble strips. This is to reduce potential for drivers to shift to the right to keep off the

C-12 rumble strip and then drop a tire off the road. (Could lead to run-off-the-road or over- correction and crossing centerline.) • For application of CRS on lanes widths less than 11 ft, an engineering review is required. 25. Does your agency have a minimum traffic volume guideline for the installation of centerline rumble strips? YES: 3.2% (1) NO: 77.4% (24) 26. Does your agency have a minimum speed limit guideline for the installation of centerline rumble strips? YES: 3.2% (1) NO 74.2% (23) If YES, please elaborate: • 50 mph 27. Does your agency have a minimum crash frequency/rate guideline for the installation of centerline rumble strips? YES: 12.9% (4) NO: 67.7% (21) If YES, please elaborate: • To date NDOT has installed centerline rumble strips on a limited number of test sections where there is a significant problem with crossover type crashes. • Critical Rate Factor > 1.0. 28. Has your agency installed both centerline rumble strips and shoulder rumble strips along the same roadway? YES: 35.5% (11) NO: 38.7% (12) If YES, approximately how many miles of this dual application have been installed? • Responses range from 5 to 50 mi.

C-13 Survey Results: General Issues 29. Has your agency installed midlane rumble strips (i.e., rumble strips installed in the center of the travel lane)? YES: 0.0% (0) NO: 100.0% (29) If NO, what is the possibility that your agency would consider installing midlane rumble strips on an experimental basis? Highly unlikely: 61.5% (16) Willing to consider: 34.6% (9) High likelihood: 3.8% (1) Note: Three states actually responded “YES” to this question, but after several follow-up telephone conversations, it was determined that either the state respondent misunderstood the question or simply provided an incorrect response. 30. Does your agency have statewide or district level data in electronic format that contains information concerning the application of shoulder and/or centerline rumble strips (e.g., implementation dates, design information, etc.)? YES: 29.0% (9) NO: 58.1% (18) 31. Does your agency install rumble strips... Only as part of larger projects? 6.5% (2) As a stand-alone safety improvement? 6.5% (2) Both situations? 83.9% (26) 32. Does your agency have data on bicycle only crashes or non-crash injuries related to rumble strip encounters? YES: 0% (0) NO: 100% (31)