Accommodation of Bicyclists and Nearby Residents in Rumble Strips/Stripes Policies

Transcription

1 TRB 0 Accommodation of Bicyclists and Nearby Residents in Rumble Strips/Stripes Policies Mohamed M. Ahmed*, Ph.D., P.E. Department of Civil and Architectural Engineering University of Wyoming Laramie, Wyoming 0 (0) -0 Fax: (0) -, mahmed@uwyo.edu Mirza A. Sharif Department of Civil and Architectural Engineering University of Wyoming Laramie, Wyoming 0 (0) -, mahammad@uwyo.edu Khaled Ksaibati, Ph.D., P.E. Department of Civil and Architectural Engineering University of Wyoming Laramie, Wyoming 0 (0) -0 Fax: (0) -, Khaled@uwyo.edu Christopher Planche ECAM Lyon 0 Montée St Barthélémy Lyon, France Tel: (0) 0-; christopher.planche@ecam.fr * Corresponding Author July 0 Prepared for Presentation at the th Transportation Research Board Annual Meeting and Possible Publication in the Transportation Research Record Word count: words + tables + figures = 0 equivalent words

2 Ahmed et al. 0 0 ABSTRACT Rumble strips/ stripes are used by many states as a relatively low cost proven safety countermeasure to reduce or prevent lane departure crashes through providing a vibrotactile and audible warning to inattentive motorists. Although the advantages of rumble strips were generally found to outweigh the disadvantages, several issues and concerns have been identified regarding the implementation of rumble strips; noise, maintenance, and the adverse effects on bicyclists are among the most recognized concerns. Safe accommodation of all road users is being considered by most transportation agencies. Particularly, many agencies are updating their rumble strips policies to accommodate bicyclists and address noise issues. The main objective of this paper is to synthesize current practices of different state agencies on accommodation of all road users in the rumble strips/stripes design. A thorough review of the literature and multiple survey questionnaires were conducted in this study to enrich the body of knowledge about rumble strips practices and to gather information about the concerns of different rumble strips road users. Department of Transportations (DOTs) have been surveyed to obtain information regarding their recent provisions to accommodate all road users in rumble strips/ stripes application. Moreover, several issues regarding the use of rumble strips/ stripes including construction, maintenance, and noise are discussed. This study demonstrated that despite the fact that rumble strips have been used for many years, there are no standardized practices used in the US. The information provided in this paper will provide the necessary background for DOTs when it comes to developing an effective all road users friendly rumble strips policy. Keywords: Rumble Strips/ Stripes Policy; Accommodating All Road Users; Bicyclists; Noise; Nearby Residents

3 Ahmed et al INTRODUCTION A rumble strip is a raised or grooved pattern placed on the pavement surface of a travel lane or shoulder (). Rumble strips intend to provide motorists with an early warning audible and tactile sensation as they approach a decision point of critical importance to their safety or to alert motorists that their vehicle has partially or completely left the travel lane. When a vehicle passes over a rumble strip, a sudden rumbling sound is caused due to the vibration of the vehicle. Rumble strips are also used to warn motorists of upcoming changes like toll plazas, change lanes for a work zone, horizontal curves, stop for a traffic signal or steer back onto the roadway. Rumble strips are also beneficial in guiding motorists in rain, fog, snow or dust. Roadway departure crashes are considered as the most severe crashes. This includes singlevehicle-run-off-road crashes (SVROR), opposite direction sideswipe, and head-on crashes. According to Federal Highway Administration (FHWA) (),,0 fatal lane and road departure crashes occurred in 0 which caused, fatalities. Researchers show that fatal and injury crashes can be reduced by using shoulder rumble strips. Head on and opposite sideswipe crashes can be reduced to a lower number by installing centerline rumble strips. Rumble strips can also decrease total number of crashes. According to the Highway Safety Manual (HSM) 00 (), rumble strips are proven to reduce lane and road departure crashes by 0 % to % on different types of roadways. Although the advantages of rumble strips were generally found to outweigh the disadvantages, several issues and concerns have been identified by the FHWA regarding the implementation of rumble strips; noise and the effects on bicyclists are among the most discussed concerns in the literature. Noise caused by vehicles driving on rumble strips may affect surrounding residents; many agencies consider noise and environmental impacts before implementing rumble strips near residential or in urban areas (-). Several studies showed that special considerations should be made to alleviate the adverse effects that rumble strips might pose on bicyclists (, - ). FHWA requires the design and installation of rumble strips to accommodate all road users. Cyclists are uniquely identified as being negatively affected most by rumble strips in situations where rumble strips are constructed on the shoulder without leaving room for cyclists. The cyclists are forced to ride on the travel lanes where they are exposed to more dangers from vehicular traffic. To prevent or reduce the negative impact of rumble strips on cyclists, and other road users, the American Association of State Highway and Transportation Officials (AASHTO), FHWA and some DOTs have provided guidelines for installing rumble strips on roadways. Rumble strips are applied in almost every state. However, studies showed that their application varies from one state to another. Some states use mostly shoulder rumble strips while others combine centerline and shoulder rumble strips. Some consider bicyclists while other do not. Additionally, agencies have different requirements for rumble strips dimensions, minimum shoulder width and etc. This inconsistency in the application of rumble strips is reflected in the guideline of every state. While some states have just started to provide some provisions for all road users, others have fully considered other road users, while some states are still following the National Cooperative Highway Research Program (NCHRP ) guideline (). The main goal of this paper is to provide an up to date synthesis of rumble strips policies and guidelines being used by different Department of Transportation and their approaches to accommodate all roadway users including nearby residents.

4 Ahmed et al BACKGROUND OF RUMBLE STRIPS/STRIPES IN THE US Applications and Types of Rumble Strips Rumble strips are placed on paved surfaces of roadway shoulders or centerlines. When these rumble strips are painted with retro-reflective coating to make them more visible, they are referred to as rumble stripes. Rumble strip applications are categorized into three basic types; ) Shoulder Rumble Strips (SRS) / Edge Line Rumble Stripes (ELRS), ) Center Line Rumble Strips or Stripes (CLRS), and ) Transverse Rumble Strips or Stripes (TRS). Shoulder Rumble Strips are a series of milled, rolled, formed, or raised longitudinal safety features that are installed near the outside edge of paved roadways with the purpose of alerting inattentive drivers when they are departing from the travel lane (). Shoulder rumble strips are placed on roadways to basically improve roadway safety that is related to unintentional drift over the road edge. Occasionally, a type of shoulder rumble strip is built by placing the rumble strips exactly at the edge of the travel lane and coating them with edge line pavement markings and this type is called Edge Line Rumble Stripes. Center Line Rumble Strips (CLRS) are also a series of raised or milled longitudinal safety features but unlike Shoulder Rumble Strips, they are located at or near the centerline of a paved roadway (). CLRS are installed to improve roadway safety in relation to inattentive drivers drifting across the centerline. Transverse Rumble Strips (TRS) consist of a series of raised or milled safety features crossing the roadway surface to provide a timely and audible warning for drivers when approaching a spot where a deceleration or a stop action is required (). Another type is midlane rumble strips which is still a conceptual design. When the driver tracks a path leading to an encroachment on the roadside, the midlane rumble strip acts on the inside tire (as opposed to the outside tire for shoulder rumble strips) to alert the driver. They serve two functions of the SRS and CLRS combined. According to NCHRP Report 00 (), midlane rumble strips could help in reducing cross-over and run-off-road crashes. Midlane rumble strips are similar in design to shoulder rumble strips, but installed in the center of the travel lane instead of the edge of the shoulder. Midlane rumble strips are promising in eliminating the adverse effect on bicyclists on roads with no or narrow shoulders, however, they could be a concern for motorcyclists. With respect to rumble strip/ stripe installation; milled rumble strips are currently the prevalent type used among the main four types; milled, rolled, formed, and raised rumble strips. Milled rumble strips are easily installed by machinery milling a new or an existing asphalt and Portland cement concrete (PCC) roadways. Rolled rumble strips must be only installed by a roller during the compaction process of pavement surfaces. It should be noted that each of the four types produces different amounts of vibrations and noise levels. The level of noise and vibration generated from milled rumble strips is superior to all other types and hence milled rumble strips are more effective in reducing lane departure crashes. For example, the Virginia DOT has demonstrated that the -inch milled rumble strips generate % more noise, and produce 0% more vibration excesses than rolled-in patterns (). In 00, the FHWA recommended milled shoulder rumble strips due to their superior performance in providing a loud and jarring warning over rolled-in rumble strips (). Rumble Strips/ Stripes Policies and Guidelines in the US In 00, NCHRP and the American Association of Highway and Transportation Officials (AASHTO) published guidance on the design of shoulder and centerline rumble strips (). The

5 Ahmed et al main objective was to minimize the adverse effects of rumble strips implementation on nonconventional vehicles and nearby residents. Nonetheless, rumble strips practices and adherence to the NCHRP and AASHTO vary widely by state. There is no single standard design for rumble strips utilized across the US. DOTs Survey With the help of WDOT, information regarding the state of practice of rumble strips/ stripes in the US were obtained. Information were collected through a review of the literature, online survey and communications with states DOTs. Twenty nine states responded to the online survey. Only four agencies have fully adhered to the NCHRP guidelines; Idaho, Mississippi, Nevada, and New Mexico. Fifteen agencies indicated that they are using the guidelines provided by NCHRP with some modifications to suit their regions needs. Seven agencies are using their own guidelines; Alabama, Kentucky, Massachusetts, New Hampshire, North Dakota, Texas, and Wyoming. Among the agencies which took the survey, only Oklahoma responded that they do not have a written policy for rumble strips. Based on the DOTs guidelines identified recently from the literature and survey responses, thirty-seven state agencies have already made provisions to accommodate bicyclists. Only three agencies responded that they do not have any provisions for bicyclists while the remaining eleven state agencies indicated that they do not have adequate information to address this issue. Based on the DOTs guidelines identified recently from the literature review and survey responses, Figure was prepared to illustrate the DOTs with provisions to accommodate bicyclists. The rest of the survey results showed that many DOTs are still updating their rumble strips policies. DOTs which had already been using their own guidelines are now moving forward to accommodate the non-conventional vehicles and nearby residents. About % of the states are following the NCHRP Report guideline, either strictly or with some modifications. Application criteria and maintenance practices vary by state. Shoulder rumble strips are more widely used than centerline rumble strips or shoulder rumble stripes. Rumble strips are installed mostly on rural roadways since they possess fewer constraints on installation criteria. Although the NCHRP issued guidance on how state agencies can balance the increase in rumble strips implementation while accommodating all roadway users, % of state DOTs indicated that their policies do not have any provisions for bicyclists when installing rumble strips. In addition, only % of DOTs consider noise when installing rumble strips. Most DOTs commented that they try to avoid installing rumble strips in urban areas to prevent noise. Moreover, only % of DOTs responded about having crash report of bicyclists/motorcyclists due to the presence of rumble strips. The governing criteria ranked by DOTs when a roadway is considered for installing rumble strips are in the following order; area type (urban vs. rural), guardrail, pavement type, pavement thickness, bicycle traffic, motorcyclists, noise, nearby residents. Four states; Kentucky, Maine, Michigan, and New Hampshire used warning signs to alert bicyclists and motorcyclists of the presence of rumble strips. Michigan DOT uses warning sign when construction activities cause traffic to shift over rumble strips. Noise caused by vehicles driving on rumble strips may affect surrounding residents. In fact states received complaints about the noise. As a result, states have taken noise into consideration when installing rumble strips near residential areas and states use alternative rumble strips design. Concerning rumble strips guidelines, the states of Wyoming, Oregon, Pennsylvania and Connecticut, reported that they are currently updating their guidelines to accommodate new

6 Ahmed et al findings from research and guideline. Several states are interested in documenting the effectiveness of rumble strips. Fifteen states recently have evaluated the performance of rumble strips and states are still working on it. ISSUES ASSOCIATED WITH RUMBLE STRIPS Impact on Bicyclists FHWA requires that the design and installation of rumble strips should accommodate all road users. Cyclists are uniquely identified as being negatively affected most by rumble strips because in situations where rumble strips are constructed on the shoulder without leaving room for cyclists, the cyclists are forced to ride on the travel lanes where they are exposed to dangers from vehicular traffic. To prevent/reduce the negative impact of rumble strips on cyclists and other road users, AASHTO, FHWA and some State DOTs have provided specific guidelines for installing rumble strips on roadways with bicyclists. SRS or ELRS could be a problem for bicyclists as most bikers ride their bicycle on shoulders. When shoulder width is inadequate, bicyclists may have to ride over the rumble strips which can cause certain types of risk. The vibrations from rumble strips can lead bicyclists to lose control of their bicycles. Debris or a parked vehicle may block the shoulder, and, it becomes necessary for the bicyclists to cross the rumble strips to move into the lane and go around obstacles (). Many agencies are working on finding suitable design to accommodate bicyclists. Some of the steps taken include providing gaps after a certain length for bicyclists. Across the country, various state agencies use different spacing, for example ft every ft, 0 ft every 0 ft, and 0 ft every 0 ft. Another way of addressing this issue is reducing the depth of the grooves which will cause fewer vibrations and therefore will be less uncomfortable for the bicyclists while producing enough vibrations for the motorists. Previously, most agencies used 0.0 in groove depth, but currently, they are using 0. in groove depth. In 00, Outcult () did a study for Colorado DOT to design bicycle friendly rumble strips. After experimenting with various dimensions and patterns, the study recommended using a groove depth of 0. in and to provide ft. gaps every ft. The study found that 0. in. groove depth is enough to provide adequate levels of vibrations and noise to alert drivers. Many state agencies do not install rumble strips if there is not enough space for bicyclists to ride their bikes on the shoulder. According to practices in many states, rumble strips should not be installed if the shoulder width is less than ft.

7 Ahmed et al. FIGURE : States Rumble Strips Policies and Provisions for Bicyclists.

8 Ahmed et al Wyoming Bicyclists Survey In order to study the effect of shoulder rumble strips on bicyclists comfort and safety in Wyoming, a survey questionnaire was conducted. Fifty-six bicyclists responded to a set of questions about their opinions and experiences with rumble strips. In this study, various means to collect bicyclists contact information were obtained by: contacting bike shops, attending bike summits and events, and contacting bike clubs on Facebook and online websites. It should be mentioned that conducting survey questionnaires in Wyoming is challenging because of the rural nature and the low population size. It is worth mentioning that participants would provide a margin of error of % at a 0% confidence level for Wyoming population size which is slightly greater than 00,000 people. The survey was completed by a sample of bicyclists from different locations, gender, age, and riding experience. Bicyclists ride their bikes mostly on state highways, city and county roads, as a hobby or to go to work. The survey indicated that % of bicyclists encountered rumble strips while riding their bikes and they feel safer since the presence of shoulder rumble strips creates a physical barrier between cyclists and vehicular traffic. Even if rumble strips might lessen the controllability of their bikes, % of bicyclists stated that they never had any crashes due to them. More than % of respondents reported that they do not need any advance warning signs for rumble strips neither do they consider rumble strips when choosing their routes. In addition, 0% of bicyclists do not feel uncomfortable riding on shoulder rumble strips. Bicyclists showed a great understanding of the importance and purpose of shoulder rumble strips. However, they indicated that having a clean and large enough clear shoulder will increase their ride-ability comfort and safety, without having to cross the shoulder rumble strips to the adjacent traffic lane. The bicyclists were asked to rank several features by which they can be accommodated better in a roadway with rumble strips, the results have been presented in Table. One-third of the respondents indicated that feet clear shoulder width would be enough for them to ride comfortably on roads with shoulder rumble strips, as shown in Figure. As shown in Figure, using rumble strips with ft gaps in 0 ft cycle was suggested by % of the respondents. The results are coherent and suggest that bicyclists are getting used to shoulder rumble strips and tolerate their presence. % % % % ft ft ft ft More than ft Min Clear Shoulder (ft) FIGURE : Minimum Clear Shoulder Preference from Bicyclists Survey 0%

9 Ahmed et al. 0 % 0% 0 ft gaps in 0 ft cycles ft gaps in 0 ft cycles ft gaps in ft cycles % FIGURE : Recommended Gaps Pattern from Bicyclists Survey 0 0 TABLE : Bicyclists Opinion about Rumble Strips Installation Rank Bicyclists' Opinion Increase shoulder width 0 Sweep shoulder more Place SRS closer to the traffic lane Use narrow SRS Do not install on roads with significant bicycle traffic Accommodation of Bicyclists in Different States Many states have already taken steps to accommodate bicyclists on highways with rumble strips. Alaska DOT provides ft gaps in 0 ft cycles (0). However, on roadways with heavy bicycle volume, gaps are provided in 0 ft cycles. Arizona DOT installs 0. in deep groove instead of 0.0 in on non-controlled access highway (). Moreover, in long grooves are recommended to use on undivided roads with shoulder width less than ft to provide more space for the bicyclists. Similarly, Arkansas DOT provides ft gaps in 0 ft cycles with 0. in deep groove (). If there is not enough shoulder width available, California DOT guidelines prohibit installing rumble strips or recommends widening the shoulder (). Colorado DOT (CDOT) recommends providing wide spacing besides changing the dimensions. The recommended spacing is in (). Additionally, it is recommended to educate the bicyclists about where to expect bicyclists and what to do when encounter them. Delaware DOT does not recommend installing rumble strips on roadways with shoulder width less than ft for the bicyclists accommodation (). However, if the shoulder width cannot be maintained, it is recommended to install edgeline rumble stripes with ft gaps in 0 ft cycles. Idaho DOT provided ft in gaps in 0 ft cycles on all rural two-lane highways and divided highways with rumble strips to allow bicyclists on roadway (). Iowa DOT also provides gaps for bicyclists to cross over on roads with rumble strips (). Twelve ft gaps are provided in each 0 ft cycles. Maryland DOT updated their policy in 0 which incorporate the accommodation of bicyclists on the roadway with rumble strips (). A skip pattern of ft in 0

10 Ahmed et al ft cycles are recommended. Moreover, Minimum ft clear shoulder width is provided on roadways with posted speed limit between 0 to miles per hour (mph). The recommended length, width, and depth should be in, in, 0. in, respectively instead of traditional in, in, and in dimensions. Based on a study on bicyclists and drivers, Michigan DOT () recommends providing ft shoulder width for bicyclists accommodation. Minnesota DOT s rumble strips policy suggests providing ft gaps in 0 ft cycles for routes with high bicycle traffic. According to the Montana DOT s guideline published in 0, where bicycle usage is consideration and the shoulder width is between ft to ft, it is recommended installing reduced lateral width rumble strips adjacent to the outside edge of travel lane (0). North Carolina Dot also recommends providing ft clear shoulder width for bicyclists (). Additionally, gaps should be provided with varying length of or ft on right shoulder on 0 or 0 ft cycle. No gaps are recommended on left shoulders. North Dakota DOT provides 0 ft gaps in 0 ft cycles on the undivided highways (). Utah DOT s guideline does not recommend installing rumble strips where shoulders are used by bicyclists unless there is ft clear width from the rumble strips to the outside edge of paved shoulder, or ft to adjacent guardrail, curb or other obstacles (). Table provides extensive information regarding the dimensions of rumble strips, minimum shoulder and lane width required to install rumble strips in a roadway. The Table also highlights additional information for bicyclists and noise issues. Gray shaded cells in Table provide specific guidelines for bicyclists accommodation. Noise Although the main purpose of using rumble strips is to warn drivers through audible sound and vibrations, this generated noise could be an issue for nearby residents. Several studies have been performed to develop a rumble strips design that generate acceptable level of noise without sacrificing benefits to motorists. A study was done by Minnesota DOT () reported, at 0 ft distance, noise level produced by a vehicle driving over a rumble strips is comparable to a truck passing by on a standard, non-rumbled surface. At 00 ft from the road, the average sound level measured, was found to be equivalent to the sound produced during a normal conversation. Another study conducted by Michigan DOT () used a 00 Ford F-0 at 0mph speed to measure the noise at different distances. The study reported a. and decibel increase over the average daytime freeway noise level at ft and 0 ft distances from the roadway respectively. Nowadays, DOTs are using alternative design (e.g. shallow depth, and shorter length) to reduce noise. In addition, DOTs have limited use of rumble strips near residential areas due to noise complaints from residents. Rumble strips are warranted in urban/ residential areas if only specific locations have frequent crash history. Wyoming Nearby Residents Survey A survey was conducted to investigate the effect of the noise associated with rumble strips on nearby residents in the state of Wyoming. A set of survey questions were presented to residents living close to rumble strips. The survey was disseminated by mail, online, and by conducting door to door interviews targeting residents living near rumble strips. Among the 0 respondents,.% are living within 00 ft from rumble strips. About % of the interviewed residents indicated that the noise from rumble strips is not an issue and did not care about completing the survey. Although intermittent residential rumble strips design is utilized in urban areas in Wyoming, two thirds of nearby residents can still hear the noise caused by rumble strips. Half of the residents categorized the level of noise as moderate. The survey results indicated that residents who live within 00 ft at

11 Ahmed et al the first line of houses might notice the noises most, but the first line of houses serves as a noise barrier for houses farther away and hence noise level is negligible for houses behind the first line. Eighty four percent of the nearby residents find the noise level acceptable while % of them are ready to tolerate it since rumble strips save lives. In fact, most of the residents experienced rumble strips as drivers and attest of its effectiveness in enhancing drivers safety. About % responded they were surprised when came in contact with rumble strips for the first time and % responded that they were alerted by rumble strips when they veered from their traffic lanes. Moreover, % of them think that the vibrations and noise created by rumble strips are enough to alert drivers. To conclude, residents would mostly like to have if possible a quieter design, and the idea of a sound barrier was mentioned a few times in residents general comments. Dimensions Various agencies use different dimensions for their rumble strips. Since the publication of the NCHRP guideline (), most of agencies have modified or are in the process of updating their policies. According to Table, the lengths of shoulder rumble strips vary from to in. Some agencies use the same length for all types of roadway regardless of locations and users. Whereas, other agencies vary the length of SRS based on roadway types, and volumes of bicyclists. Idaho varies their strip length between in to in depending on the shoulder width. Minnesota DOT and New Hampshire DOT install in strips on interstate and in along strips on other highways. Also, Arizona DOT changes the strip length to in and in based on shoulder width on undivided highways. The most common length used by most agencies for SRS in undivided highways are in to provide more space for the bicyclists. For the width of the strips, most agencies use either in or in depending on the area type. Previously, agencies used 0.0 in or more of groove depth which made loud sound. But, after various studies, researchers have found that 0. in groove can produce enough auditory and vibratory sound to alert the drivers. There are still a few agencies that use 0. in or 0. in groove for their rumble strips. Shapes A study was performed by the Kansas DOT () to compare the football and rectangular shaped rumble strips to determine which one is the most efficient and quieter while ensuring safety. Several tests were done to compare these two shapes of strips. They were examined in order to determine how long it takes for water and debris to be removed from the grooves. Both football and rectangle shape rumble strips performed similarly on water and debris accumulation/removal. Another test was designed to measure the noise and vibration levels generated inside vehicles by the two shapes. The study concluded that there is no significant difference between the two rumble strips shapes. However, it was determined from the bicyclist surveyed that football shaped rumble strips are more preferred.

12 Ahmed et al. Table : Provisions for Bicyclists Accommodation in Shoulder Rumble Strips Guidelines in the US State Length Depth Spacing Bicycle gap ft (m) Min. Lane ft (m) Min. Shoulder ft (m) Noise Consideration Comments Alaska (0.) (.) 0.0 (.) (0.) ft. / 0 ft. (. m. /. m.) cycle ft. / 0 ft. (. m. /. m.) cycle (high bicycle traffic) (.), (.) (w/ guardrail) Do not install on pavements less than cm. ( in.) thick Alabama (0.) (.) 0. (.) (0.) 0 ft. / 0 ft. (.0 m. /. m.) cycle ft. / 0 ft. (. m. /. m.) cycle n/a (0.) N Arizona (.) (0.) (.) 0. (0.) (0.) 0 ft. in 0 ft. (.0 m. in. m.) cycle (.) (.), (.) (w/ guardrail) Do not place rumble strips within 00 feet of receptors Arkansas (0.) (.) 0. (0. ) (0.) 0 (.0) '" (.) California (0.) ± (.±.) 0. (0.) (0.) es (.) Colorado (0.) (.) 0. (0.) (0.) (.) (w/ guardrail) Connecticut (0.) (.) 0.0 (.) (0.) n/a (.) N Delaware (0.) (.) 0. (0.) (0.) Florida (0.) Idaho (0.).-. (.- ).-. (.- ) (.-.) (.-.) ± (0.±. ) (0.) Indiana (0.) (.) (0.) ft. in ft. (. m. in.0 m.) cycle 0 ft. in 0 ft. (.-.0 m. in. m.) cycle (.) (.) (.) (.) (.) N Skip array is standard array. Only used in rural areas. Do not install in urban areas

13 Ahmed et al. State Length Depth Spacing Bicycle gap ft (m) Min. Lane ft (m) Min. Shoulder ft (m) Noise Consideration Comments Kentucky (0.) (.) 0.0±0. (.±0.) (0.) No Provision (.) (.), (.) (w/ guardrail) Maine Massachusetts (0.) (.) 0.0 (.) (0.) ft. in ft. (. m. in. m.) cycle (.) Do not install in intersection and bridge decks Michigan (0.) (.) 0.±0. (0.±0.) (.) (.) Minnesota (0.).-. (.- ) (0.-.) (0.) (.) Missouri (0.) (.).0± 0. (0.±0.0 ) (0.) (.) (.), (.) (w/ guardrail) Do not install in intersection, or residential areas Montana (.) 0. (0.) es (.) Nevada (.) (.) New Hampshire (0.) (.) (0.) (0.-.), (.-.) (0.) (.), (.)(w/ guardrail) New Mexico (0.) (.), (0.) (if no Bicyclists) 0.0 (.) (0.) es (.), (.) (w/ guardrail) New Jersey (0.) (.) 0.0 (.) (0.) No provision n/a (.)

14 Ahmed et al. State Length Depth Spacing Bicycle gap ft (m) Min. Lane ft (m) Min. Shoulder ft (m) Noise Consideration Comments Pennsylvania (0.) ±0.0 (.±.) 0.±0.0 (0.±0.) (0.) (.) (.) Do not install at intersection and bridge decks South Carolina (0.) (.) 0.0 (.) (0.) (.) (.) N South Dakota (0.).-. (.- ) (.-.0) (0.) ft. in ft. (. m. in. m.) cycle (NI) (.) (.) N Should not be placed in ramps and gore areas. Tennessee 0 ft. in 0 ft. (.0 m. in. m.) cycle Virginia (0.) (.) 0.0 (.) (.) (.) Washington (0.).-. (.-.) (.-.) (0.) (.), (.)(w/ guardrail ) Wisconsin (.) N Wyoming (0.) (.) (0.-.) (0.) * Some states are still updating their guidelines, and, for some others, they don t have all the specifications. = es. N= No. n/a (.) N

15 Ahmed et al CONCLUSIONS The systematic implementation of a low-cost improvement such as shoulder and centerline rumble strips might be the key to significantly reducing crashes and fatalities. A thorough review of the literature and multiple survey questionnaires were conducted in this study to enrich the body of knowledge about rumble strips practices and to gather information about the concerns of different rumble strips road users. The information gathered indicated that many State DOTs have updated or they are in the process of updating their rumble strips/ stripes policies. To increase safety on two-lane highways, combined shoulder and centerline rumble strips are being installed by various transportation agencies where speeds are greater than mph with substantial traffic volume, or a history of lane departure and head-on related crashes. As indicated from the State DOTs survey, accommodating all road users such as providing a Bicycle Friendly Rumble Strips is considered by many state DOTs. In general, DOTs guidelines do not recommend installing shoulder rumble strips on routes designated as a bicycle routs or high bicycle-use areas. Some DOTs polices have mitigated the adverse effect of rumble strips on bicyclists through various remedial measures such as: providing feet clear shoulders, or feet with guardrail as the bare minimum to ensure sufficient space for bicyclists. States such as Alaska and Colorado require a minimum feet shoulder. Florida requires at least feet of continuous clear riding surface where bicyclists are expected. Adjusting rumble strips placement and dimensions such as placing shoulder rumble strips as close to the edge line, and using narrower and shallower designs are other remedial measures used by several states. If combined shoulder and centerline rumble strips are used on narrow roads with bicycle traffic, a modified lateral width rumble strips is considered to mitigate the adverse effect on vehicle/ bicycle interaction. Providing periodic gaps of at least feet every 0 feet are commonly utilized to enhance cyclists maneuverability to avoid debris along the shoulder, turn, or pass other cyclists. Among the survey responses, it was found 0 percent use this gap pattern. Rumble strips installation in mountainous highways should be studied further. Several bicyclists commented on the unique riding experience on roadways with steep downhill grades and shoulder rumble strips. Bicyclists requested a longer gaps on steep downhill sections for a safer maneuverability as the speed increases sharply. Drivers are usually more awake when driving through mountainous roadway than flat roads. Further considerations of providing adequate length of SRS gaps should be taken before installing rumble strips in mountain areas. The results from the bicyclists survey conducted as part of this study as well as information gathered in earlier surveys indicated that bicyclists are satisfied with Bicycle Friendly Rumble Strips design. It is clear from the survey results that if adequate gaps and shoulder widths are provided, then bicyclists can comfortably ride on roads without hitting rumble strips or risk being hit by passing vehicles. Many states consider nearby residents when installing rumble strips in residential areas by either not installing rumble strips within urban limits or if warranted by crash experience, a modified shallower depth rumble strips are used. Nineteen states out of the survey respondents consider noise issue before installing rumble strips. More than 0 percent of the states are using shallower depth of 0. inch to mitigate the noise in residential areas. The results from this study also indicated that the increase in centerline rumble strips implementation would not affect other non-conventional vehicles such as motorcyclists.

16 Ahmed et al The systematic implementation of a low-cost improvement such as shoulder and centerline rumble strips might be the key to significantly reducing crashes and fatalities, if the noise and bicyclists issues are considered during the rumble strips design. This study demonstrated that despite the fact that rumble strips have been used for many years, there are no standardized practices used in the US. The information provided in this paper will provide the necessary background for DOTs when it comes to developing an effective all road users friendly rumble strips policy. ACKNOWLEDGEMENTS The authors wish to thank the Wyoming Department of Transportation (WDOT) for funding this research. All opinions and results are solely those of the authors. REFERENCES. Harwood, D. W., Enhancing Highway Safety with Rumble Strips, Transportation Research News, Issue:, pp: -. May,.. FHWA Safety Website Accessed on July, 0.. AASHTO 00, Highway Safety Manual, Chapter.. Gardner, L. W., M. J. Rys, and E. Russell, Comparison of Football Shaped Rumble Strips versus Rectangular Rumble Strips, Final Report K-Tran: KSU -00. Kansas Department of Transportation, May 00. Bucko, T. R., and A. Khorashadi, Evaluation of Milled-In Rumble Strips, Rolled-In Rumble Strips and Audible Edge Stripe, Office of Transportation Safety and Research, California Department of Transportation, April 00. Russell, E. R., and M. J. Rys, NCHRP Synthesis : Centerline Rumble Strips. TRB, National Research Council, Washington, D.C., 00.. Elefteriadou, L., M. El-Gindy, Torbic, D. J., P. Garvey, A. Homan, Z. Jiang, B. Pecheux, and R. Tallon, Bicycle-Tolerable Shoulder Rumble Strip, Report Number: PTI K. The Pennsylvania State University, The Pennsylvania Transportation Institute, 000. International Organization of Standardization, Mechanical Vibration and Shock Evaluation of Human Exposure to Whole-Body Vibration Part : General Requirements, ISO, International Organization of Standardization, Geneva, Switzerland,.. oung, T., Bicycle Use on Highways with Rumble Strips, Test Report U.S. / Hoback Canyon, Teton County, Wyoming,. 0. Gårder, P., Rumble Strips or Not Along Wide Shoulders Designated for Bicycle Traffic?, Transportation Research Record No. 0, TRB, National Research Council, Washington, D.C.,.. Outcalt, W., Bicycle-Friendly Rumble Strips, Report No. CDOTDTD-R-00-. Colorado Department of Transportation Miller, K. W., Effects of Center-Line Rumble Strips on Non-Conventional Vehicles, Minnesota Department of Transportation, 00.. Federal Highway Administration, Synthesis of Shoulder Rumble Strip Practices and Policies, Executive Summary, U.S. Department of Transportation, Accessed August 0.. FHWA Technical Advisory, Roadway Shoulder Rumble Strips, T 00., 00.

17 Ahmed et al National Cooperative Highway Research Program, NCHRP Report : Guidance for the Design and Application of shoulder and Centerline Rumble Strips, 00. Federal Highway Administration, Types of Rumble Strips, / Accessed June 0.. Srinivasan R., Baek J., and Council F., Safety Evaluation of Transverse Rumble Strips on Approaches to Stop-Controlled Intersections in Rural Areas, FHWA-HRT--0, 00.. National Cooperative Highway Research Program, NCHRP Report 00, A Guide for Addressing Run-Off-Road Collisions, 00. Chen, C. A Study of Effectiveness of Various Rumble Strips on Highway Safety, Virginia Department of Transportation, Richmond,. 0. Alaska DOT Policy on Rumble Strip Installation, Alaska Department of Transportation, 00. Section 0, ADOT Traffic Engineering Policies, Guidelines, and Procedures, Arizona Department of Transportation, 0. Policy for the Use of Rumble Strips, Arkansas State Highway and Transportation Department, 0. Guidelines for Installation of Rumble Strips, California Department of Transportations, 0. Rumble Strips, Standard Plan No: M--, Colorado Department of Transportation, 0. Continuous Centerline and Longitudinal Edgeline Rumble Strips, Design Guidance Memorandum, Delaware Department of Transportation, 0. Shoulder Rumble Strips and Rumble Stripes, Standard Drawing No: C--A, Idaho Transportation Department, 0. Milled Rumble Strips, Iowa Department of Transportation, 0. Guideline for Application of Rumble Strips and Rumble Stripes, State Highway Administration, Maryland Department of Transportation, 0. Datta, T.,K., Gates, T., J., and Savolainen, P. T., Impact of Non-Freeway Rumble Strips-Phase, Report No: RC, Michigan Department of Transportation, 0 0. Rumble Strips Guidance, Montana Department of Transportation, 0. Revised Rumble Strips Guideline, Roadway Design Manual, North Carolina Department of Transportation, 00. Rumble Strips Standard Drawing, North Dakota Department of Transportation, 0. Rumble Strips Typical Application, Standard Drawing No: PV, Utah Department of Transportation, 0. HDR Engineering, Inc., Rumble Stripe Noise Study Report, Number: -0 Minnesota Department of Transportation, 0.. Rumble Strip, Center Line, M-, Noise Measurements Hagar Shores, Michigan, Michigan Department of Transportation, November, 00.. Margaret J. Rys, Gardner, L., and Russell, Eugene., Evaluation of Football Shaped Rumble Strips Versus Rectangular Rumble Strips, Journal of the Transportation Research Forum, Vol., No. ; 00, pp. -