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

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23 S E C T I O N 5 This section presents a summary of existing rumble strip practices and policies. This section focuses on the typical dimensions of shoulder and centerline rumble strips and the criteria that control installation practices of shoulder and cen- terline rumble strips. The information presented in this section is pulled from multiple sources. The primary source of infor- mation is the results of a survey conducted in fall 2005 as part of this research. The survey was distributed via email to the 50 U.S. state transportation agencies and 12 Canadian pro- vincial transportation agencies to identify existing policies/ guidelines governing the design and application of shoulder and centerline rumble strips on rural and urban highways. Responses from 27 U.S. state transportation agencies and 4 Canadian provincial transportation agencies were received. The survey asked questions related to the following topics: • lateral placement with respect to edgeline/centerline, • lane width, • shoulder width, • clear path, • traffic volume, • posted speed, • crash history, • pavement type, • pavement depth, • presence of designated bicycle route, • spacing, and • geometric configuration of the roadway. A copy of the survey questionnaire is provided in Appen- dix B. Since a number of recent surveys (32,36,45,46,58–62) on rumble strips have been conducted, the results of these surveys were reviewed prior to developing the survey for this research. This was done to avoid unnecessary duplication of ques- tions. Thus, this section presents a compilation of infor- mation from these surveys as well. In addition, a number of recent syntheses documents have been published and so infor- mation from these documents serves as supplemental material for this section. These synthesis documents include: • Synthesis of Practices for the Implementation of Centerline Rumble Strips (56), • NCHRP Synthesis 339: Centerline Rumble Strips (36), • Synthesis of Best Practices for the Implementation of Shoulder and Centerline Rumble Strips (57), • Synthesis of Shoulder Rumble Strip Practices and Policies (63), and • Technical Advisory: Roadway Shoulder Rumble Strips (64). Typical Shoulder and Centerline Rumble Strip Practices in North America Various types, patterns, and designs of shoulder rumble strips are used in most states within the United States, but not all Canadian provinces install shoulder rumble strips. Table 6 summarizes shoulder rumble strip practices within North America. Table 6 is divided into five sections. The first section (Column 1) simply indicates the state or Canadian province. The second section (Columns 2 to 4) provides information on pattern characteristics including information on the types of roadways where shoulder rumble strips are installed, the type of rumble strip (i.e., milled, rolled, formed, or raised), and details of a skip pattern if preferred over continuous place- ment. The third section (Columns 5 to 12) provides infor- mation concerning minimum requirements for installation as it relates to minimum shoulder widths, lateral clearances, average daily traffic (ADT), pavement depth, speed, acci- dent frequencies/rates, bicycle considerations, and placement distances with respect to the edgeline of the travel lane. The fourth section (Columns 13 to 16) provides dimensions of the shoulder rumble strips used by the respective states. The final section (Column 17) indicates the effective date of the policy from which some, or all, of the information found in the table for the respective state was obtained. Because the response rate Existing Rumble Strip Practices and Policies

Table 6. Summary of North American shoulder rumble strip practices. snoisnemiDnoitallatsnirofstnemeriuqermuminiMscitsiretcarahcnrettaP State or province* Roadway type Rumble type** Skip Pattern Shoulder width Lateral clearance ADT (vpd) Pavement depth Speed Accident Bicycle Offset (A) Length (B) Width (C) Depth (D) Spacing (E) Date of policy M Continuous N N N N N N N 18 in. 16 in. 7 in. 0.5 – 0.625 in. 12 in. – Alabama* U frwy; U multilane divided; R freeway; R multilane divided; R multilane undivided; R two-lane RL Continuous N N N N N N N 0 in. 3 ft 1 in. 0.5 in. 8 in. 10/93 Alaska U frwy; U expwy U two-lane R frwy R expwy R two-lane M 6 ft Gap 40 ft Cycle 10 ft Gap (edgeline) 6 ft 4 ft – 2 in. 45 mph N Y 2 in. for 6 in. shldr 6 in. for > 6 in. shldr 16 in. 7 in. 0.5 in. 12 in. 5/01 Arkansas* U frwy; R frwy M Continuous N N N N N N N 4 in. 16 in. 7 in. 0.5– 0.625 in. 12 in. – 0 in. 6 in. 7 in. ± 0.25 in. 0.375 in. 12 in. ± 1 in. Arizona* R frwy; R multilane divided; R multilane undivided; R two-lane M 10 ft Gap 40 ft Cycle 3–6 in. 2 in. N N N N Y 10 in. 8 in. or 12 in. 7 in. ± 0.25 in. 0.375 in. 12 in. ± 1 in. 5/03 M Continuous 4 ft 5 ft N N N N Y 6–12 in. 12 in. 5 in. 0.32 in. ±125 in. 12 in. RL Continuous 4 ft 5 ft N N N N Y 6–12 in. 12 in. 2 in. 1 in. 8 in. California R frwy R expwy R two-lane RS Continuous 4 ft 5 ft N N N N Y 6–12 in. – – – – 9/02 M 12 ft Gap 60 ft Cycle 4 ft 6 ft N Y N N N 0 in. 12 in. 5 in. 0.375 in. 12 in. Colorado* R frwy; R frwy ramps R multilane divided; R multilane undivided; R two-lane RL,F 12 ft Gap 60 ft Cycle 4 ft 6 ft N Y N N N 0 in. 12 in. 2.375 in. 0.5–1 in. 4 in. 10/00 Connecticut* U frwy; R frwy M Continuous 3 ft 4 ft N N N N N 6 in. (median) 12 in (outside) 16 in. ± 0.5 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. ± 0.5 in. 10/99

Delaware* U frwy; U multilane divided; U multilane undivided; U two-lane; R freeway; R multilane divided; R multilane undivided; R two-lane M Continuous N N N N N N Y 12 in. 16 in. 7 in. 0.5 in. 12 in. – M 11 ft Gap 28 ft Cycle N N N N N N N 16 in. 16 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. ± 1 in. – RS (asphalt) – N N N N N N N 0 in. 28 in. 2 in. 0.5 in. 12 in. – Florida U frwy R frwy RS (Thermoplastic) – N N N N N N N 0 in. – 4 in. Min 0.5 in. – – Georgia* U frwy; U frwy ramps; U multilane divided; U multilane undivided; U two-lane; R frwy; R frwy ramps; R multilane divided; R multilane undivided; R two-lane M 12 ft 4 ft 4 ft 400 N N N N 8–12 in. 16 in. 7 in. 0.5– 0.625 in. 12 in. – Hawaii – – – – – – – – – – – – – – – Idaho* R frwy; R multilane divided; R multilane undivided; R two-lane M 12 ft Gap 60 ft Cycle 3 ft N N N N N N 0 in. 12– 18 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. 5/05 Illinois – M Continuous – Varies – – – – – 12 in. 16 in. 7 in. 0.5 in. 12 in. 1/03 (continued on next page)

snoisnemiDnoitallatsnirofstnemeriuqermuminiMscitsiretcarahcnrettaP State or province* Roadway type Rumble type** Skip Pattern Shoulder width Lateral clearance ADT (vpd) Pavement depth Speed Accident Bicycle Offset (A) Length (B) Width (C) Depth (D) Spacing (E) Date of policy Indiana* R frwy; R frwy ramps; R multilane divided; R multilane undivided M 20 ft Gap 100 ft Cycle 4 ft 7 ft N 5 in. N N Y 0–6 in. 16 in. 7 in. 0.5 in. 12 in. 3/03 Iowa* U frwy; U multilane divided; U multilane undivided; R freeway; R multilane divided; R multilane undivided; R two-lane M 12 ft Gap 60 ft Cycle 4 ft N 3,000 N N N Y 0 in. 16 in. 7 in. 0.5– 0.625 in. 12 in. 1/04 4/05 Kansas R hwy M Intermittent 8–10 ft N N 1 in. N N N 16 in. 16– 17 in. 7–8 in. 0.5 in. 12 in. 3/01 M Continuous N N N Variable N N N 12 in. 16 in. 7 in. ± 0.5 in. 0.5 in. ± 0.125 in. 12 in. ± 1 in. – Kentucky* U frwy; U frwy ramps; U multilane divided; U multilane undivided; U two-lane; R frwy; R frwy ramps; R multilane divided; R multilane undivided; R two-lane RL Continuous N N N Variable N N N 0 in. 24 in. 1.5 in. ± 0.25 in. 0.75 in. ± 0.25 in. 9 in. ± 1 in. – Louisiana – – – – – – – – – – – – – – – – Maine* U frwy; R frwy M – – – – 3 in. – – – 0 in. 16 in. 7 in. 0.5– 0.75 in. 12 in. – Maryland – M Continuous N – – – – – – 6–12 in. 16 in. Min 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. 3/04 Table 6. (Continued).

Massachusetts U frwy; U multilane divided; U multilane undivided; R freeway; R multilane divided; R multilane undivided; R two-lane M Continuous 2 ft N N N 40 mph N N 4 in. 16 in. 7 in. 0.5 in. 12 in. 12/04 Michigan – M Continuous 4 ft – – – – – – 12 in. 16 in. 7 in. 0.5– 0.625 in. 12 in. 8/04 Minnesota* U frwy; U multilane divided; U multilane undivided; R freeway; R multilane divided; R multilane undivided; R two-lane M 12 ft Gap 60 ft Cycle 6 ft N N N 50 mph N Y 4 in. 12– 16 in. 7 in. ± 0.5 in. 0.375– 0.5 in. 12 in. ± 0.5 in. 5/00 Mississippi* U frwy; U multilane divided; R frwy; R multilane divided M Continuous 2 ft 4 ft N N N N N 0 in. 15 in. 7 in. 0.5– 0.625 in. 12 in. 10/04 Missouri* U frwy; U multilane divided; U multilane undivided; U two-lane; R freeway; R multilane divided; R multilane undivided; R two-lane – Continuous 2 ft N N 3.75 in. 50 mph N N 0 in. – – – – – Montana Interstates Primary routes M Continuous 4 ft N N N N N N 6 in. 12– 16 in. 7 in. 0.5– 0.75 in. 12 in. 3/96 (continued on next page)

snoisnemiDnoitallatsnirofstnemeriuqermuminiMscitsiretcarahcnrettaP State or province* Roadway type Rumble type** Skip Pattern Shoulder width Lateral clearance ADT (vpd) Pavement depth Speed Accident Bicycle Offset (A) Length (B) Width (C) Depth (D) Spacing (E) Date of policy F Continuous 4 ft N N N N N N 6 in. 12– 16 in. 2 in. 1 in. 4.5 in. 3/96 Nebraska – M – – – – – – – N 0 in. 16 in. 7 in. 0.5 in. 12 in. – Nevada* R frwy; R multilane divided; R multilane undivided; R two-lane M Continuous 6 ft N N N N N Y 4 in. 16 in. 7 in. 0.5– 0.625 in. 12 in. 1/01 New Hampshire R frwy M Continuous – – – – – – N 6–30 in. 16 in. 7 in. 0.5 in. 12 in. – New Jersey U frwy R frwy M Continuous 3 ft (median) 8 ft (outside) N N N N N N 4 in. 16 in. 7 in. 0.5 in. 12 in. – New Mexico R frwy R expwy R two-lane M Continuous – – – – – – – 12 in. 16 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. Min 8/98 New York R frwy U frwy M Continuous N 34 in. N 2.5 in. N N Y Varies 16 in. 7 in. 0.5– 0.625 in. – 6/97 North Carolina* U frwy; U multilane divided; R freeway; R multilane divided; R two-lane M 6 ft Gap 40 ft Cycle 6 ft N N 6 in. N N Y 0 in. 16 in. 7 in. 0.5 in. 12 in. 3/05 North Dakota* R frwy; R multilane divided; R multilane undivided; R two-lane M 12 ft Gap 50 ft Cycle 4 ft 4 ft 2,000 N 45 mph N N 0 in. Varies 6.5 in. ± 0.5 in. 0.5 in. ± 0.125 in. 12 in. 5/23/03 Ohio R frwy U frwy M 10 ft Gap 20 ft Cycle 4 ft 4 ft – – – 0.25 acc/MVM Y 4–6 in. 16 in. 7 in. 0.5 in. 12 in. – Oklahoma Multilane Two-lane M Continuous 4 ft N N 2 in. N N N 24 in. ± 3 in. 16 in. ± 1 in. 7 in. ± 1 in. 0.5– 0.625 in. 12 in. 99 Oregon* R frwy; R multilane divided; R multilane undivided; R two-lane M Continuous – 4 ft – – – – N 0 in. – 5.5 in. 0.5 in. ± 0.125 in. 18 in. 5/05 Table 6. (Continued).

Pennsylvania* U frwy; U frwy ramps; U multilane divided; U multilane undivided; R frwy; R frwy ramps; R multilane divided; R multilane undivided; R two-lane M (Interstate) Continuous 4 ft (median) 8 ft (outside) N N N N N N 12 in. ± 0.5 in. (median) 18 in. ± 0.5 in. (outside) 16– 17 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. 4/95 M (non-Interstate) Continuous 6 ft 4 ft 1,500 – ≥ 55 mph N Y 6 in. 16 in. 5 in. ± 0.5 in. 0.375 in. ± 0.0625 in. 12 in. ± 0.5 in. M (non-Interstate) Continuous 6 ft 4 ft 1,500 – < 55 mph N Y 6 in. 16 in. 5 in. ± 0.5” 0.375 in. ± 0.0625 in. 11 in. ± 0.5 in. M (edgeline) Continuous 4–6 ft 4 ft N N N N Y 0 in. 6 in. 5 in. ± 0.5 in. 0.375 in. ± 0.0625 in. 12 in. ± 0.5 in. 3/02 Rhode Island* U frwy; U frwy ramps; U multilane divided; U multilane undivided; R frwy; R frwy ramps; R multilane divided; R multilane undivided; R two-lane M Continuous N N N N N N N 4 in. (median) 12 in. (outside) 16 in. 7 in. 0.5 in. 12 in. – South Carolina – – – – – – – – – – – – – – – – South Dakota – RL Continuous – – 2,500 – – – N 8 in. 36 in. 2 in. 1 in. 8 in. – (continued on next page)

Tennessee R frwy U frwy M Continuous N – – – – N N 6 in. 16 in. Min 6 in. ± 0.5” 0.375– 0.5 in. 18 in. ± 0.5 in. – M Continuous 4 ft (median) 8 ft (outside) 6 ft – – – – Y 0 in. 16 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. RL Continuous 4 ft (median) 8 ft (outside) 6 ft – – – – Y 4–8 in. 24 in. 2 in. 1 in. ± 0.125 in. 8–9 in. Texas* R frwy; R multilane divided; R multilane undivided; RS Continuous – – – – – – Y – – – – – 5/99 Utah* U frwy; R frwy; R frwy ramps; R multilane divided; R multilane undivided; R two-lane M 12 ft Gap60 ft Cycle N 4 in. N N N N N Varies 12 in. 8 in. ± 0.375 in. 0.625– 0.75 in. 12 in. 1/05 Vermont* U frwy; R frwy; R multilane divided; R multilane undivided M Continuous N 4 ft N N N N Y 6–30 in. 16 in. 7 in. 0.5 in. 12 in. – Virginia* R frwy M Continuous N N N N N N N 0 in. 16 in. 7 in. 0.5 in. 12 in. – Washington* U frwy; R frwy; R multilane divided; R multilane undivided; R two-lane M 12 ft Gap 40 ft Cycle; 12 ft Gap 60 ft Cycle; 16 ft Gap 64 ft Cycle 4 ft N N Variable 45 mph .6/mi or 34/100 MVMT Y 6 in. 16 in. 7 in. ± 0.5 in. 0.5– 0.625 in. 12 in. 8/04 West Virginia – – – – – – – – – – – – – – – – Wisconsin R frwy R expwy U frwy U expwy M – N – – – – N N 30 in. 16 in. 7 in. 0.5– 0.625 in. 19 in. ± 1 in. – Wyoming* R frwy; R multilane undivided; R two-lane M 12 ft Gap 60 ft Cycle 2 ft N N N 45 mph N N 6 in. 16 in. 7 in. 0.5– 0.625 in. 12 in. 9/01 snoisnemiDnoitallatsnirofstnemeriuqermuminiMscitsiretcarahcnrettaP State or province* Roadway type Rumble type** Skip Pattern Shoulder width Lateral clearance ADT (vpd) Pavement depth Speed Accident Bicycle Offset (A) Length (B) Width (C) Depth (D) Spacing (E) Date of policy Table 6. (Continued).

Canadian Provinces M 12 ft Gap 24 ft Cycle – – – – – – – 6–8 in. 12 in. 5–7 in. 0.32– 0.5 in. 11–14 in. – Alberta – RL Continuous – – – – – – – 3–6 in. 24 in. 1.5–2 in. 0.5– 0.625 in. 7.5–8.5 in. – British Columbia* R frwy; R multilane divided; R two-lane M Continuous 5 ft 4 ft N N N N N 4 in. 12 in. ± 0.375 in. 5.5 in. ± 0.75 in. 0.32 in. ± 0.125 in. 12 in. 4/04 New Brunswick – M Continuous – – – – – – – 8 in. 12 in. 6 in. 0.375– 0.5 in. 12 in. – Ontario* R frwy; R two lane M Continuous 2 ft 3 ft N 3 in. N N Y 4 in. 12 in. 6 in. ± 0.75 in. 0.375 in. ± 0.125 in. 12 in. 10/00 Prince Edwards Island* N/A – N/A – – – – – – N N/A – – – – – Quebec – M Continuous – – – – – – – 12 in. 16 in. 7 in. 0.5 in. 12 in. – M 13 ft Gap 26 ft Cycle 6 ft N 1,800 N N N Y 6–7 in. 12 in. 6 in. ± 1 in. 0.32 in. ± 0.125 in. 12 in. 2/05 Saskatchewan* R frwy; R frwy ramps; R multilane divided; R multilane undivided; R two-lane RL Continuous 6 ft N 1,800 N N N Y 0 in. 24 in. 1.5– 2.0 in. 0.5 in. 7.5–8.5 in. – * Indicates state/province responded to survey and information from the survey is reflected in this table. ** Rumble Strip Type Abbreviations: M = Milled RL= Rolled RS = Raised F = Formed.

of the survey conducted as part of this project was not 100 per- cent, and because the research team tried to utilize responses from the most recent surveys and syntheses, there is the pos- sibility that some of the information presented in Table 6 may not reflect the most current practice of the respective state. However, Table 6 attempts to provide the most up-to-date and comprehensive information available on shoulder rum- ble strip practices in North America. Table 7 summarizes centerline rumble strip practices within North America. Similar to Table 6, Table 7 is divided into five sections. The primary difference between the two tables is that under pattern characteristics for centerline rumble strips, there is no column for skip patterns, and Column 4 now indicates the lateral placement of the centerline rumble strip applica- tions relative to the centerline pavement markings and lane. In addition, under minimum requirements for installation for centerline rumble strips, Column 5 indicates the minimum lane width requirements rather than the minimum shoulder width and lateral clearance requirements, which are more applicable to shoulder rumble strips. Summary of Survey Responses This section summarizes the responses to the survey con- ducted as part of this research received from 27 U.S. state trans- portation agencies and 4 Canadian provincial transportation agencies. As noted earlier, Tables 6 and 7 are based on a broader data set, because they also include information gathered in earlier surveys and from synthesis documents. 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 transportation agencies to further explain an issue, the actual responses are provided in bullet form in Appendix C. 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 avail- able on the Internet: Arizona, Iowa, Indiana, Minnesota, North Carolina, North Dakota, Nevada, Oregon, Penn- sylvania, Texas, Utah, Virginia, Washington, and British Columbia. 2. On what types of roadways does your agency install shoul- der 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 shoul- der rumble strips on both the right (outside) and left (median) shoulder? YES: 93.5% (29) NO: 6.5% (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? • Typical responses included: (a) the offsets are different typically with smaller offsets on the left (median) shoul- der and (b) rumble strips are installed continuously on the left (median) shoulder while intermittent gaps are provided on the right (outside) 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: • Several agencies only install shoulder rumble strips on asphalt shoulders and prohibit the use on PCC shoul- ders. Some agencies indicated that standards for place- ments differ, primarily to account for joints in PCC surfaces. 32

snoisnemiDnoitallatsnirofstnemeriuqermuminiMscitsiretcarahcnrettaP State or province* Roadway type Rumble type** Placement Lane width ADT (vpd) Speed Accident Pavement depth Bicycle Length (B) Width (C) Depth (D) Spacing (E) Date of policy Alabama* R two-lane Into lane N N N N N N – – – – – Alaska – M 12 in. 5–7 in. 0.5 in. 10–12 in. – Arkansas* R two-lane Within pm N N N N N N – – – – – Arizona* R multilane undivided, R two-lane M Within pm Into lane N N N N N N – – – – – ––––––––––––––ainrofilaC Colorado* R multilane undivided, R two-lane M Within pm N N N N Varies N 12 in. 5 in. 0.375 in. 12 in. 6/02 Delaware* U multilane undivided; R multilane undivided, R two-lane M Into lane N N N N N N 16 in. 7 in. 0.5 in. 12 in. – Hawaii – M – – – – – – – 18–24 in. 4 in. – 24 in. – Idaho* R multilane undivided, R two-lane – Within pm Into lane N N N Y N N – – – – – Iowa* R two-lane – Into lane N N N N N N – – – – – Kansas M – – – – – – – 12 in. 6.5 in. 0.5 in. 12 in. 12 in. and 24 in. – Kentucky* R two-lane M Into lane N N N Y Varies N 24 in. 7 in. 0.5–0.625 in. 24 in. – Maine* B multilane undivided – Into lane N N N N 3 in. N – – – – – Maryland – M – – – – – – – 18–24 in. 4 in. 0.5 in. varies – Massachusetts – M – – – – – – – 16 in. 6 in. 0.5 in. 12 in. – Michigan – M – – – – – – – 16 in. 7 in. 0.375 in. 19 in. – Minnesota* R two-lane M Beside pm N N 50 mph N N N 12–16 in. 7 in. 0.5 in. 19 in. – Missouri* R two-lane M Within pm N N N N 3.75 in. N 12 in. 6.5 in. 0.5 in. 12.5 in. – Nebraska – M – – – – – – – 16 in. 7 in. 0.5–0.625 in. 12 in. – Nevada* U multilane undivided; R multilane undivided, R two-lane – Into lane N N N Y N N – – – – – North Carolina* R two-lane – Into lane Beside pm N N N N 6 in. N – – – – – Oregon* R multilane undivided, R two-lane M Within pm Into lane N N N N N N 16 in. 7 in. 0.5 in. 12 in. – Table 7. Summary of North American centerline rumble strip practices. (continued on next page)

snoisnemiDnoitallatsnirofstnemeriuqermuminiMscitsiretcarahcnrettaP State or province* Roadway type Rumble type** Placement Lane width ADT (vpd) Speed Accident Pavement depth Bicycle Length (B) Width (C) Depth (D) Spacing (E) Date of policy M Within pm Into lane 10 ft Y N Y N N 16 in. 7 in. ± 0.5 in. 0.5 in. ± 0.0625 in. 24 in. and 48 in. Pennsylvania* U multilane undivided; R multilane undivided, U two-lane R two-lane M Within pm Into lane 10 ft Y N Y N N 14–18 in. 7 in. ± 0.5 in. 0.5 in. ± 0.0625 in. 24 in. 3/02 Texas* R multilane undivided, R two-lane M Into lane N N N N N N 16 in. 7 in. 0.5 in. 17 in. – Utah* R multilane undivided, R two-lane M Into lane N N N N N N 12 in. 8 in. 0.625– 0.75 in. 12 in. – Virginia* U multilane undivided; R multilane undivided, R two-lane M, RS Within pm N N N N N N 16 in. 7 in. 0.5 in. 12 in. – Washington* R multilane undivided, R two-lane M Within pm 12 ft N N N Varies N 16 in. 5 in. 0.375 in. 12 in. – Wisconsin – – – – – – – – – – – – – – Wyoming* R two-lane M Into lane – N N N – N 12 in. 7.5 in. 0.5 in. 14.5 in. – Canadian Provinces – Alberta – M – – – – – – – 12 in. 6–8 in. 0.2–0.35 in. 13–15 in. – British Columbia* R multilane undivided, R two-lane M Within pm > 11 ft Eng. review N N N N N 12 in. ± 0.375 in. 5.5 in. ± 0.75 in. 0.32 in. ± 0.125 in. 12 in. 5/04 Ontario* R two-lane M Within pm N N N N 3 in. N 12 in. 6 in. ± 0.75 in. 0.375 in. ± 0.125 in. 12 in. – Saskatchewan* R multilane undivided, R two-lane M Within pm Into lane N N N N N N 12 in. 4–7 in. 0.315 in. ± 0.079 in. 10–13 in. – * Indicates state/province responded to survey and information from the survey is reflected in this table. ** Rumble Strip Type Abbreviations: M = Milled RS = Raised Table 7. (Continued).

5. How close to the edgeline does your agency install shoulder rumble strips? • Responses ranged from flush against the edgeline (i.e., 0 in. [0 mm]) to 30 in. (762 mm) 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? • Responses included: (a) snow plowing considerations, (b) whether the installation was on the right (outside) shoulder or the left (median) shoulder, and (c) shoulder width/lateral clearance requirements. 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.)? • Responses included: (a) entrance and exit ramps; (b) when the lateral clearance is less than required; (c) when turn lanes are provided; (d) at intersections, driveways, and median crossings; (e) near residential areas; (f) near catch basins; (g) near pavement joints; (h) bicycle routes; (i) structures; (j) where curb and gutter are installed; (k) when posted speed is 45 mph (70 km/h) or less; and (l) in urban areas. 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: 16.1% (5) • Other responses included: (a) condition of existing shoulder, and (b) scheduled upgrades for the facility. 8. Does your agency have a minimum shoulder width require- ment for the installation of shoulder rumble strips? YES: 61.3% (19) NO: 35.5% (11) If YES, please elaborate: • Responses ranged from 2 to 6 ft (0.6 to 1.8 m), but 4 ft (1.2 m) and 6 ft (1.8 m) were the most common responses. 9. Does your agency have a minimum lateral clearance require- ment for the installation of shoulder rumble strips? YES: 45.2% (14) NO: 51.6% (16) If YES, please elaborate: • Responses ranged from 2 to 7 ft (0.6 to 2.1 m), but 4 ft (1.2 m) was the most common response. 10. Does your agency have a minimum traffic volume require- ment for the installation of shoulder rumble strips? YES: 16.1% (5) NO: 83.9% (26) If YES, please elaborate: • Responses ranged from 400 to 3,000 veh/day. 11. Does your agency have a minimum pavement depth require- ment for the installation of shoulder rumble strips? YES: 25.8% (8) NO: 74.2% (23) If YES, please elaborate: • Responses ranged from 3 to 6 in. (76 to 152 mm). One respondent had a minimum requirement of 1.75 in. (44 mm) for the final surface. Also several respondents had a general depth requirement but no minimum depth specified. 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 (70 to 80 km/h). 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: • Respondents indicated that they compared the SVROR crash frequency to the statewide average. 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) 35

Centerline rumble strips extend into travel lane: 48.4% (15) If YES, please elaborate: • Responses included: (a) rumble strips are not installed along designated bicycle routes, (b) need to consider available lateral clearance, (c) rumble strip patterns/ dimensions change, and (d) gaps are provided rather than installing the rumble strips on a continuous basis. 15. Does your agency’s policy provide a gap in the shoulder rum- ble 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: • Common responses were 10 or 12 ft (3.0 or 3.6 m) gaps in 40 or 60 ft (12 or 18 m) cycles. One respondent increases the gap and cycle lengths when longer rumble strips are installed. 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)? YES: 29.0% (9) NO: 71.0% (22) If YES, please elaborate: • Common responses included: (a) based upon crash history, and (b) at horizontal curves. 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) 19. Has your agency’s policy/practice of installing shoulder rum- ble strips changed recently (i.e., within the last 3 to 5 years)? YES: 48.4% (15) NO: 51.6% (16) If YES, how has it changed? • Common responses included: (a) now install intermit- tent gaps and (b) discontinued the use of rolled rumble strips. 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? • Responses included: (a) adopting a written policy when no policy previously existed, (b) adopting a policy for other roadway types, (c) modifying the depth dimen- sion, and (d) changing the length of intermittent gaps. 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? 36 Centerline rumble strips within pavement markings: 38.7% (12)

YES: 35.5% (11) NO: 38.7% (12) If YES, approximately how many miles of this dual applica- tion have been installed? • Responses ranged from 5 to 50 mi (8 to 80 km) Survey Results: General Issues 29. Has your agency installed midlane rumble strips (i.e., rum- ble 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 ques- tion, but after several follow-up telephone conversations, it was determined that either the 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 6.5% (2) projects? As a stand-alone safety 6.5% (2) improvement? 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) 33. We are currently setting priorities for the research in NCHRP Project 17-32. Your opinion would be appreciated. Please rank the priority for research to address gaps in knowledge associated with SHOULDER rumble strips. Please rank each research need on a 1 (Low Priority) to 5 (High Priority) scale. Table 8 presents the survey responses to Question 33 in prioritized order. The higher priority issues are provided at the top of the table, while the low priority issues are provided at the bottom of the table. 37 Centerline rumble strips on either side of pavement markings: 6.5% (2) 23. On what type of roadways does your agency install center- line 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: • The responses were 10 ft (3.0 m), 11 ft (3.3 m), and 12 ft (3.6 m) (combined lane and shoulder width). 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) If YES, please elaborate: • 1,500 ADT 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 (80 km/h) 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) 28. Has your agency installed both centerline rumble strips and shoulder rumble strips along the same roadway?

34. Please rank the priority for research to address gaps in knowledge associated with CENTERLINE rumble strips? Please rank each research need on a 1 (Low Priority) to 5 (High Priority) scale. Table 9 presents the survey responses to Question 34 in prioritized order. The higher priority issues are provided at the top of the table, while the low priority issues are provided at the bottom of the table. Summary of Key Findings From Existing Rumble Strip Practices and Policies The following key points are drawn from the recent rum- ble strip surveys and synthesis documents: • It is believed that at least 46 out of the 50 state transpor- tation agencies within the United States install shoulder rumble strips on at least one type of roadway; however, several state transportation agencies do so without a writ- ten policy. • Shoulder rumble strips are being installed on a wide variety of roadway types including urban freeways, urban freeway on-ramps and off-ramps, urban multilane divided highways (nonfreeways), urban multilane undivided highways (non- freeways), urban two-lane roads, rural freeways, rural free- way on-ramps and off-ramps, rural multilane divided highways (nonfreeways), rural multilane undivided high- ways (nonfreeways), and rural two-lane roads. The majority of the installations are on rural roads compared to urban roads. It should be pointed out that the numbers shown in response to Question 2 of the survey may be somewhat mis- leading in terms of the total mileage of shoulder rumble strip installations along the respective roadway types. As part of the safety evaluation of shoulder rumble strips conducted during this research, several of the responding agencies that indicated in their survey response that they installed rumble strips on a wide range of the respective roadway types were contacted. However, in requesting sites with rumble strips for inclusion in the safety evaluation, several of the agencies had difficulty identifying sites with rumble strips covering the full range of roadway types or, in some cases, indicated that the mileage for certain roadway types was extremely low. 38 Priority ranking Unresolved issue Avg. value Min. value Max. value 518.3htdiwredluohsmuminimenimreteD Better quantify safety effectiveness (along different types of roads) 3.7 1 5 Determine optimum lateral placement from the edgeline 3.6 1 5 514.3ecnamrofreptnemevapnotceffeenimreteD Determine impact of noise produced by rumble strips on adjacent residents 3.3 1 5 Determine minimum level of stimuli (i.e., sound or vibration) necessary to alert a drowsy or inattentive driver 3.3 1 5 511.3seitivitcaecnanetniamnotceffeenimreteD Better quantify safety effectiveness (along varying roadside conditions—e.g., 10 ft clear zone vs. 20. ft clear zone vs. 30 ft clear zone) 3.1 0 5 Better quantify safety effectiveness (along varying roadway geometry) 3.0 1 5 Determine optimum dimensions (e.g., length, width, depth, spacing) 3.0 1 5 Determine optimum longitudinal gaps in rumble strips to provide accessibility for bicyclists 2.8 0 5 Improve physical design of rumble strips with respect to rideability for bicyclists and motorcyclists 2.8 1 5 Better quantify safety effectiveness (differences in rumble strips installed along the right (outside) vs. left (median) shoulders) 2.8 0 5 Better quantify safety effectiveness (along roadways with varying speeds or ADT) 2.8 1 5 Better quantify safety effectiveness (under varying conditions— e.g., wet vs. dry, light vs. dark, etc.) 2.7 0 5 Other—determine benefit of painting edgelines through shoulder rumble strips (1 respondent) 4.0 4 4 Other—determine effect of rumble strips in edgeline pavement marking from safety, visibility, and durability aspect (1 respondent) 5.0 5 5 Table 8. Transportation agency responses concerning future research needs related to shoulder rumble strips.

Based upon the survey results and our experience in trying to identify sites with shoulder rumble strips for inclusion in the safety evaluation, we found that a significant number of miles of shoulder rumble strips are installed along urban freeways, rural freeways, rural multilane divided highways, and rural two-lane roads, and significantly less mileage of shoulder rumble strips are installed along urban multilane divided highways, urban multilane undivided highways, urban two- lane roads, and rural multilane undivided highways. • Written shoulder rumble strip policies and specifications differ considerably by the shoulder pavement surface type (i.e., concrete or asphalt). • Rumble strip policies incorporate a wide range of criteria that directly impact installation requirements for shoulder rumble strips. These criteria include the following: – Roadway type – Shoulder width  26 transportation agencies specify a minimum shoul- der width requirement within their written policy.  Minimum requirements range from 2 to 10 ft (0.6 to 3.0 m), with 4 ft (1.2 m) being the most common value.  Several transportation agencies have different mini- mum requirements for different types of roads. – Lateral clearance  16 transportation agencies specify a minimum lateral clearance requirement within their written policy.  Minimum requirements range from 2 to 7 ft (0.6 to 2.1 m), with 4 ft (1.2 m) and 6 ft (1.8 m) being the most common values.  Several transportation agencies specify both a min- imum shoulder width requirement and a lateral clear- ance requirement, and in several cases the lateral clearance requirement is greater than the shoulder width requirement. For these cases, it must be assumed that the lateral clearance is measured to the closest fixed object on the roadside, beyond the outside edge of the paved shoulder. – ADT  5 transportation agencies specify minimum ADT lev- els within their written policy.  Minimum ADT levels for rumble strips range from 400 to 3,000 veh/day, but a majority fall between 1,500 and 3,000 veh/day. – Bicycles  16 transportation agencies address bicycle consider- ations in some manner within their written policy. 39 Priority ranking Unresolved issue Avg. value Min. value Max. value Determine effect on visibility of pavement markings 3.8 1 5 Operational impacts on vehicular traffic (i.e., vehicle speeds and lateral placement) 3.7 1 5 Determine optimum dimensions (e.g., length, width, depth, spacing) 3.7 1 5 Assess advantages/disadvantages of installing centerline rumble strips in passing zones 3.6 1 5 Determine optimum placement with respect to the centerline markings 3.6 1 5 Better quantify safety effectiveness (along different types of roads—e.g., two-lane highway, multilane highways, etc.) 3.5 1 5 Determine effect on pavement performance 3.4 1 5 Better quantify safety effectiveness (along varying roadway geometry) 3.2 0 5 Better quantify safety effectiveness (installed in combination with shoulder rumble strips) 3.2 1 5 Determine impact of noise produced by rumble strips on adjacent residents 3.0 0 5 Determine effect on maintenance activities 3.0 1 4 Better quantify safety effectiveness (along roadways with varying speeds or ADT) 2.9 1 5 Better quantify safety effectiveness (under varying conditions) 2.8 0 5 Improve physical design of rumble strips with respect to rideability for bicyclists and motorcyclists 2.6 1 5 Other—potential effect of centerline rumble strips on longitudinal pavement joints (1 respondent) 4.0 4 4 Other—determine effect of rumble strips in edgeline pavement marking from safety, visibility, & durability aspect (1 respondent) 5.0 5 5 Table 9. Transportation agency responses concerning future research needs related to centerline rumble strips.

– Pavement type  Several transportation agencies only install shoulder rumble strips on asphalt shoulders.  Pavement type impacts the placement of the rumble strips because of joints in PCC surfaces. – Pavement depth  8 transportation agencies specify a minimum pave- ment depth requirement within their written policy.  Minimum requirements range from 1 to 6 in. (25 to 152 mm). – Area type  Most transportation agencies install shoulder rumble strips in rural areas.  27 transportation agencies install shoulder rumble strips in urban areas. – Speed limit  8 transportation agencies have a speed limit require- ment in their written policy. – Crash frequencies/rates  2 transportation agencies have a crash frequency/rate requirement within their written policy. • A variety of shoulder rumble strip types are used in North America. These include milled, rolled, raised, or formed. Based on noise and vibration research, milled rumble strips generally provide higher in-vehicle noise and vibration levels than rolled rumble strips. Currently, milled rumble strips are the preferred type among most transportation agencies. • Transportation agencies have varying policies concerning where rumble strips are installed with respect to the edge- line. Offset distances range from 0 to 30 in. (0 to 762 mm). Eighteen transportation agencies have installed rumble strips on the edgeline of the travel way. Other common off- set distances are 6 to 12 in. (152 to 305 mm). Only a few transportation agencies install shoulder rumble strips with an offset distance greater than 12 in. (305 mm). Several transportation agencies specify different offsets for rumble strips installed on the right (outside) shoulder and rumble strips installed on the left (median) shoulder. Typically, the offset for the left (median) shoulder is less than the off- set for the right (outside) shoulder. • Typical dimensions for milled shoulder rumble strips are the following: – Length: 16 in. (406 mm)  Several transportation agencies install rumble strips as short as 6, 8, or 12 in. (152, 203, or 305 mm), but 16 in. (406 mm) is definitely the most common length. – Width: 7 in. (178 mm)  Widths commonly range from 5 to 7 in. (127 to 178 mm), but 7 in. (178 mm) is by far the most com- mon. At least one transportation agency installs rum- ble strips with a width of 8 in. (203 mm). – Depth: 0.5 to 0.625 in. (13 to 16 mm)  Many transportation agencies specify the depth to be between 0.5 to 0.625 in. (13 to 16 mm). A groove depth of 0.5 in. (13 mm) is also common. Several trans- portation agencies specify depths as small as 0.375 in. (10 mm). – Spacing: 12 in. (305 mm)  Most transportation agencies specify a spacing of 12 in. (305 mm). Some transportation agencies install rum- ble strips with 11 in. (280 mm) spacing, while others increase the spacing to 18 in. (457 mm). • On non-controlled access highways, it is common for trans- portation agencies to provide periodic gaps in the rumble strips of 10 or 12 ft (3.0 or 3.6 m), in 40 or 60 ft (12 or 18 m) cycles, with the primary intention to allow bicyclists to maneuver from the travel lanes to the shoulder and back (i.e., from one side of the rumble strips to the other) with- out having to encounter the indentations/grooves. • In addition to providing periodic gaps in continuous rum- ble strips to enable bicyclists to cross over the rumble strips without encountering the indentations/grooves, it is com- mon practice to discontinue or interrupt shoulder rumble strips at specific features or areas to avoid adverse conse- quences (e.g., pavement deterioration, noise, etc.). Specific features or areas along the shoulder or roadway where it is common to discontinue or interrupt shoulder rumble strips include the following: – Intersections, driveways, and turn lanes; – Entrance and exit ramps; – Structures (i.e., bridges); – Areas where the lateral clearance drops below a specified value and/or areas where the lateral clearance is limited due to adjacent guardrail, curb, or other obstacles; – Residential areas; – Catch basins and drainage grates; – Pavement joints; and – Median crossings. • Fewer transportation agencies use centerline rumble strips than shoulder rumble strips, and only a few transportation agencies that use centerline rumble strips have a written (i.e., formal) policy. The majority of centerline rumble strips have been installed on rural two-lane undivided roads; however, centerline rumble strips have been installed on rural multi- lane undivided highways and to a lesser degree on urban two- lane undivided roads and urban multilane undivided highways. The responses to Question 23 concerning the types of roadways where centerline rumble strips are installed may be misleading. While trying to identify sites with centerline rumble strips on urban multilane undivided highways, urban two-lane roads, rural multilane undivided highways, and rural two-lane roads, responding agencies that indicated they installed centerline rumble strips on such sites had difficulty 40

identifying any sites for inclusion in a safety evaluation for many of the roadway types. Based upon our experience and the survey responses, it is our opinion that centerline rumble strips are commonly installed along rural two-lane roads, and very few installations have occurred on the other three roadway types. In most cases, where centerline rumble strips have been installed along a rural multilane undivided high- way, the installation was part of an extended project along a rural two-lane road, and rather than discontinuing the centerline rumble strips along shorter multilane sections within the limits of the entire project, the rumble strips were installed on the multilane sections as well. • Although many transportation agencies incorporate a wide range of criteria that directly impact installation require- ments for shoulder rumble strips, very few criteria are spec- ified for the installation of centerline rumble strips. Two transportation agencies have a lane width requirement, one transportation agency has a traffic volume requirement, one transportation agency has a speed limit requirement, four transportation agencies have a crash frequency/rate requirement, six transportation agencies have a pavement depth requirement, and no state transportation agency directly addresses bicycle considerations for determining the installation of centerline rumble strips. • Most transportation agencies install centerline rumble strips within the boundaries of the centerline markings or a portion of the rumble strips may extend slightly into the travel lane. Only two transportation agencies install center- line rumble strips on either side of the centerline pavement markings. • All transportation agencies in North America that install centerline rumble strips use milled rumble strips. • Typical dimensions for milled centerline rumble strips are as follows: – Length: 12 or 16 in. (305 to 406 mm)  This dimension varies considerably among trans- portation agencies. Lengths range from 12 to 24 in. (305 to 610 mm). – Width: 7 in. (178 mm)  Widths commonly range from 5 to 7 in. (127 to 178 mm), but 7 in. (178 mm) is by far the most com- mon. At least one transportation agency installs rum- ble strips with a width of 8 in. (203 mm). – Depth: 0.5 in. (13 mm)  Many transportation agencies specify the depth to be 0.5 in. (13 mm). Several transportation agencies spec- ify a range for the depth from 0.5 to 0.625 in. (13 to 16 mm). Several transportation agencies specify depths as small as 0.375 in. (10 mm). – Spacing: 12 in. (305 mm)  Many transportation agencies specify a 12-in. (305-mm) spacing, but this dimension varies consid- erably, ranging from 10 to 48 in. (254 to 1220 mm), among transportation agencies. Some transportation agencies also alternate the spacing between grooves. • Midlane rumble strips are still a concept that no trans- portation agency has been willing to install, even on a trial or experimental basis. Several transportation agencies indicated that they would be willing to consider such a treatment. 41