Practice of Rumble Strips and Rumble Stripes (2016)

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3 This list was categorized into six categories: • State departments of transportation (DOTs) general rum- ble practices • Roadway selection criteria • Design and installation • Maintenance practices • Benefits • Issues. With the cooperation and feedback of the NCHRP syn- thesis panel, an online survey was developed for distribu- tion to the state DOTs and Canadian provinces. The survey was sent to the members of the AASHTO Highway Sub- committee on Traffic Engineering. After several months and follow-ups, the survey was closed, with 41 state DOT (82% response rate) respondents and two Canadian provinces responding. KEY DEFINITIONS The following definitions, used in the questionnaire, were adapted from the FHWA guidance document on rumble strips and stripes (FHWA 2015): • A shoulder rumble strip (example below) is a longitu- dinal safety feature installed on a paved roadway shoul- der near the outside edge of the travel lane. It is made of a series of milled or raised elements intended to alert inattentive drivers (through vibration and sound) that their vehicles have left the travel lane. (FHWA definition). Rumble strips and stripes are a low cost safety countermeasure used to reduce roadway and lane departure crashes; however, their use and installation in various states are not uniform and there may not be one ideal design for all applications to deliver the auditory and tactile cues required to warn the drivers to correct their path. To address the problem of single vehicle run-off-road crashes, many transportation agencies use shoulder rumble strips or stripes to alert inattentive drivers that their vehicles have drifted out of the travel lane. Because of the documented safety benefits of shoulder rumble strips and their relatively low installation cost, transportation agencies are applying shoulder rumble strips on a widespread basis. Originally, rumble strips were installed primarily on rural freeways, but now transpor- tation agencies are installing shoulder rumble strips along divided and undivided highways in both rural and urban areas. Transportation agencies have also expanded their applica- tion of rumble strips and stripes to include installations along the center lines of undivided highways. The primary purpose of center line rumble strips and stripes is to reduce head-on crashes, opposite-direction sideswipe crashes, and, to some degree, single vehicle run-off-the-road to the left crashes; however, installing rumble strips and stripes either along the shoulder or on center lines, without considering the impacts on other highway users, may lead to unintended consequences. SYNTHESIS OBJECTIVES The purpose of this synthesis is to identify current practices used by states installing rumble strips and stripes in the expec- tation that it may assist transportation agencies, researchers, and the road-building industry in identifying successful approaches. The scope of this synthesis study focuses pri- marily on the following aspects: • Rumble designs–patterns, locations, pavement types and widths, etc. • Expected safety benefits or crash mediation in poor visibility con ditions • Tolerances for installation • Roadside noise • Impacts on bicycle community • Public outreach and education • Maintenance and durability issues • Other concerns identified through the survey. chapter one INTRODUCTION

4 • A shoulder rumble stripe (example below) is a special type of shoulder rumble strip placed directly at the edge of the travel lane with the edge line pavement marking placed through the line of rumble strips. • An intermittent gap is a gap created between continu- ous application of the rumble line for pre-determined situations such as intersections, major driveways, bridge decks, etc. • Dimensions of rumble strips and stripes (illustrated in Figure 5 in chapter three): Length: Dimension of the rumble strip measured lat- eral to the travel way. This dimension is sometimes referred to as the transverse width. Width: Dimension of the rumble strip measured parallel to the travel lane. Spacing: Distance measured between rumble strips pat- terns. Typically this dimension is measured from the center of one rumble strip to the center of the adja- cent rumble strip, or it could be measured from the beginning of one rumble strip to the beginning of the adjacent rumble strip. Typical terms used to describe this dimension are on-center spacing, spacing on- center, center-to-center spacing, or simply “spacing.” Depth: Dimension is the vertical distance measured from the top of the pavement surface to the bottom of a rumble strip pattern. This distance refers to the maximum depth of the cut or groove. REPORT ORGANIZATION The synthesis is organized into five chapters and three appendices. Chapter one contains introductory information, including background, objectives and scope, and key definitions. Chapter two summarizes a literature review, which was conducted to explore different rumble strip and stripe prac- tices included in the synthesis; and lists references (included in the bibliography) that may aid future researchers and prac- titioners interested in this topic. Chapter three documents the survey results from the 41 responding state DOTs. The two Canadian provinces had very similar practices to the state DOTs, however, they are not included in the survey results and analysis. Chapter four provides an in-depth analysis of key issues— noise, bicycle concerns, safety benefits, and pavement deterioration—identified from the synthesis results and case examples, and how some state DOTs are addressing those issues. Chapter five summarizes the synthesis findings and con- clusions, and offers suggestions on future research that may advance the rumble strip and stripe state of the practice within state DOTs. Appendix A replicates the survey; Appendix B lists the survey participants; and Appendix C offers selected agency survey responses. • A center line rumble strip (example below) is a lon- gitudinal safety feature installed at or near the center line of a paved roadway. It is made of a series of milled or raised elements intended to alert inattentive drivers (through vibration and sound) that their vehicles have left the travel lane. (FHWA definition). • A center line rumble stripe (example below) is a longi- tudinal safety feature at or near the center line and cre- ated when the center line pavement marking is placed over the center line rumble strip. • A bicycle gap pattern describes a roadway stretch clear of rumbles (typically between 10 and 12 feet) followed by a series of rumbles (typically from 40 to 60 feet).