Developing Standards and Guidelines for Establishing Speed Limits on Unpaved Roads

Transcription

1 Developing Standards and Guidelines for Establishing Speed Limits on Unpaved Roads By Joshua R. Jones, E.I.T Traffic Engineer Wyoming T 2 / LTAP University of Wyoming Laramie, WY Joel Meena, P.E. State Traffic Engineer Wyoming Department of Transportation 5300 Bishop Blvd. Cheyenne, WY Khaled Ksaibati, Ph.D., P.E. Director Wyoming T 2 / LTAP Department of Civil and Architectural Engineering University of Wyoming P.O. Box 3295 Laramie, WY Word Count: Tables/Figures * 250 Words = 7493 Words Submitted for Presentation and Publication at the 91 st Annual Meeting of the Transportation Research Board Washington, D.C., 2011

2 Jones, Meena, and Ksaibati 1 ABSTRACT The lack of national standards for establishing speed limits on unpaved roads has put pressure on local governments to make judgment calls on their road networks. Unpaved roads have unique characteristics that differ from paved roads. They usually are very low volume and were not necessarily designed by engineers. This study was conducted to determine the necessary standards and guidelines for establishing speed limits on unpaved roads in Wyoming. The process used national standards and other state practices to ensure a comprehensive methodology was followed. A focus group comprised of traffic and safety engineers was formed to find an efficient process for establishing speed limits on unpaved roads. The group focused on four main aspects for establishing speed limits: data collection requirements, roadway safety, finding the appropriate speed limit and the declaration of the speed limit. Once the standards and guidelines were developed, five different groups were asked to provide feedback to ensure that all stakeholders had an opportunity to review them. The findings of this study will help states and counties follow a similar process or be able to adopt the standards and guidelines with minor adjustments.

3 Jones, Meena, and Ksaibati 2 INTRODUCTION Establishing speed limits remains one of the more controversial tasks for the traffic engineering profession. Engineers, public safety officials, and others involved in setting and enforcing speed limits may disagree on the appropriate balance between safety and road-user convenience while considering conditions of topography, weather, road surface, adjacent activities, and traffic. Motorists, other road users, and roadway neighbors have their own perspectives on this balance and may or may not abide by the professionals judgments. If the regulation of speed is to be effective, the posted limit must be generally consistent with speeds that drivers feel are safe and proper. Enforcement is widely recognized to be crucial to the success of speed limits as a means of making roads safer. If law enforcement officers and the courts are confident that speed limits have been developed on a reasonable basis, their enforcement of the limits will be more effective. Generally, speed limits should be set at levels that are self-enforcing so that law enforcement officials can concentrate their efforts on the worst offenders. As of 2008, over 32% of the 4,058,000 miles of roads in the United States had unpaved surfaces (1). Currently, there are no national standards or guidelines for setting speed limits on unpaved roads. This has put pressure on local governments and counties to make judgment calls on the correct speed limit. A lot of states use the same criteria for setting speed limits on unpaved roads as on paved roads. This can create inconsistencies since unpaved roads have many different characteristics including: very low traffic volumes, inadequate signing, varying road conditions, narrow shoulders, varying road width, and many roadside hazards. In addition, unpaved roads frequently evolved from trails or farm access lanes and were not designed by engineers. In Wyoming a new law came into effect in 2011 that reduced the statutory speed limit on unpaved roads from 65 mph to 55 mph. Title 31, Chapter 5 Article 3 of the Wyoming Statutes establishes the speed regulations for all public roadways in Wyoming. The limits specified in this subsection established a maximum lawful speed on an unpaved roadway at 55 mph. Any speed limit, other than a statutory speed limit that is posted on a Wyoming unpaved road, must be based on an engineering study. That study should include an analysis of free-flow traffic speeds and a general roadway safety evaluation. To help counties implement the new law, the Wyoming Department of Transportation (WYDOT) and the Wyoming Technology Transfer Center (WYT²/LTAP) developed standards and guidelines for establishing speed limits on unpaved roads. The standards and guidelines were developed following a similar process that national agencies have used for paved roads. This entailed a focus group that developed a decision process for establishing different speed limits. Five different groups were contacted to get the necessary feedback from those who would be directly impacted by the new standards and guidelines. These included WYDOT, local governments at the transportation and safety congress, Wyoming County Commissioners Association (WCCA), Wyoming Associations of County Engineers and Road Superintendents (WACERS), and the general public.

4 Jones, Meena, and Ksaibati 3 The main objective of this paper is to outline the standards and guidelines which were developed. The standards establish proper study procedures for completing the engineering investigation in accordance with the statutes, provide guidance in setting appropriate speed limits based on the study data, and specify the documentation and notification procedures needed when establishing new speed limits on unpaved roads. These standards and procedures summarize the minimum requirements to establish speed limits on unpaved roads. A professional engineer can consider additional information when establishing speed limits. The guidelines described in this paper can be implemented by other agencies managing unpaved roads. NATIONAL STANDARDS AND GUIDELINES The Manual on Uniform Traffic Control Devices (MUTCD) states that when a speed limit is posted, it should be within 5 mph of the 85 th percentile speed of free-flowing traffic. However, the manual indicates other factors may influence the appropriate speed limit, including: roadway characteristics such as shoulder condition, grade alignment, and sight distance; pace speed; roadside development and environment; parking practices and pedestrian activity; and reported crash experience for at least a 12-month period (2). Even though the MUTCD indicates that these other factors can influence the speed limit decision, it does not quantify the impact of those factors on the final speed limit decision. The National Cooperative Highway Research Program has developed a web based application called US LIMITS2 which recommends a speed limit on a specific road based on information from the user. The application was developed in part to quantify the other roadway characteristics besides speed data. US LIMITS2 calculates two speed limits; the first one depends solely on roadway characteristics and the second one is calculated by considering crash data. Figure 1a shows the decision tree developed by US LIMITS2 for setting speed limits on roadways in undeveloped areas. This was highlighted because unpaved roads are more related to roadways in undeveloped areas than any of the other US LIMITS2 categories. The decision tree starts with user input to help calibrate the model. It then asks the user if crash data is available and if it is, the model calculates two speed limits. Speed limit one is based solely on the roadway characteristics. For road sections in undeveloped areas, the roadside hazard rating is the only road characteristic that is analyzed. The rating looks at the width of clear zone, side slopes, and recoverability of run off the road situations. The ratings rank from 1 being the safest to 7 having the most risk associated with it. Figure 1b shows how the speed limit one is chosen based on the rating number. The second speed limit is found by comparing crash data on similar roads and if the road section under consideration has a higher than expected crash rate, then the second speed limit is usually set lower than the 85 th percentile speed. The final speed limit is then found by taking the lower of either values.

5 Jones, Meena, and Ksaibati 4 Figure 1a: Decision Process for setting speed limits in Undeveloped Areas (3). Figure 1b: Speed Limit one Calculation on a Roadway Section in Undeveloped Areas (3).

6 Jones, Meena, and Ksaibati 5 Some of the shortcomings of the US LIMITS2 system for setting speed limits on unpaved roads include the following: There is no unpaved road option. General process may not apply to Very Low Volume Roads (ADT < 400). Roadside hazard rating may not apply to unpaved roads. Higher variance between the 85 th and 50 th percentile speeds on unpaved roads is not considered. SPEED LIMIT PRACTICES IN OTHER STATES Michigan recently passed a law limiting speed limits on unpaved roads based on the number of access points per half mile, as shown in Table 1. This law will stay in effect until Michigan State Police finish their final report on guidelines for setting speed limits on gravel roads. Table 1: Michigan Speed Limit Law on Gravel Roads (4). Access Points Design Speed per 0.5 miles < 30 In a study conducted by the Michigan DOT, The following recommendations were made with regard to establishing speed limits: Posting speed limits within 5 mph of the 85th percentile speed has a beneficial effect, although small, on reducing total crashes but has a major beneficial effect on providing improved driver compliance. Posting speed limits more than 5 mph below the 85th percentile speed does not reduce crashes and has an adverse effect on driver compliance. Speed zoning should not be used as the only corrective measure at high crash locations in lieu of other safety improvements (5). An extensive gravel road study was done by Kansas State University in That study focused on developing a system for determining the speed limit for a particular road section. They found that the speeds being traveled on gravel roads had less to do with the actual speed limit and were affected more by roadway geometrics, roadway characteristics, and drivers perceptions of safety (6). The study also found that some state DOTs, such as Oregon and Minnesota, feel that because the conditions of gravel roads are always changing, it is not logical to place a speed zone on such roads.

7 Jones, Meena, and Ksaibati 6 CalTrans doesn t provide guidelines for setting speed limits on unpaved roads but does offer a general process for setting speed limits on their roads. When a speed limit is to be posted in California, it should be established at the nearest 5 mph increment of the 85 th percentile speed of free flowing traffic. The posted speed may be reduced by 5 mph from the nearest 5 mph increment of the 85 th percentile speed. If the 5 mph reduction is applied, the conditions and justification for the reduced speed limit need to be documented in writing and be approved by a registered civil or traffic engineer (7). Texas DOT sets their speed limits based on the 85 th percentile and doesn t allow the practitioner to lower it. The procedure states that Arbitrarily setting lower speed limits at point locations due to a perceived shorter than desirable stopping sight distance is neither effective nor good engineering practice (8). For low volume roads, the Vermont DOT uses several time runs to estimate the speed instead of gathering a sample of 100 vehicles because it might require too much time to obtain the sample. They require three forms to be completed for every speed study, including those on unpaved roads, to be able to verify in court that it was done to standards. This helps give enforcement agencies the confidence to issue speeding tickets knowing that the speed limit can be verified. They also state that a spot hazard such as a sharp curve or intersection shouldn t be used to lower the speed limit. An established speed limit is a speed that will allow the driver to react to a variety of situations but does not guarantee that the speed can be maintained throughout the zone (9). WYDOT currently has standards and procedures for setting speed limits on paved roads. Their policy follows the MUTCD fairly closely but sets the lower bound of the pace speed as the lowest acceptable speed limit. The pace speed is the 10 mph increment that encompasses the highest proportion of observed speeds. When there is a wide range that a recommended speed limit can be set to, the speed limit decision relies mostly on the engineer s judgment. This can create inconsistencies of how speed limits are set across the state (10). METHODOLOGY The WYT²/LTAP and WYDOT followed a systematic process to develop the standards and guidelines for establishing speed limits on unpaved roads. It was important to get feedback from various organizations to insure successful implementation. This was critical since unpaved roads are usually the responsibility of local governments. The following is the process that was used: Conducted analysis on the WYT²/LTAP gravel roads traffic data. Met with WYDOT district traffic engineers. Developed draft standards. Obtained approval from WYDOT s chief engineer. Obtained counties feedback at the WYT²/LTAP Safety Congress. Obtained county engineers and road supervisors feedback at the WACERS meeting. Presented the standards and procedures to the Wyoming County Commissioners Association.

8 Jones, Meena, and Ksaibati 7 Incorporated input from the general public. Implemented the standards and guidelines on July 1, FOCUS GROUP The guidelines and standards were initially developed by conducting a focus group meeting at the statewide traffic engineers meeting in Wyoming. The meeting had traffic and safety engineers from multiple agencies as shown below: State Traffic Engineer District Traffic Engineers FHWA Safety Engineer State Highway Safety Engineer WYT²/LTAP Engineers Unbiased Survey The meeting began by asking the group to fill out an unbiased survey. This was done to get the individual members of the group to independently form opinions on setting speed limits on unpaved roads before the meeting started. Table 2 shows the questions that were asked, the percentage of participants choices, and any comments that were included. The group selected the minimum value for the speed limit, access points, number of crashes and surface conditions as critical variables when setting speed limits. A frequent comment was that many of the variables are reflected in the 85 th percentile and don t need to be considered separately as factors. WYT²/LTAP Gravel Road Study The next step was a presentation of the Wyoming unpaved road speed data that was collected by the WYT²/LTAP. Information on 82 Wyoming unpaved roads was collected to gain a better understanding of traffic volumes and speeds. Table 3 shows that the average 50 th percentile speed recorded was 31 mph while the average 85 th percentile speed was 40 mph. This shows that, on average, there is a 9 mph gap between the two percentiles and showed that the 50 th percentile may be too low for the lower bound of the speed limit. To understand the challenges of data collection requirements for unpaved roads, Figure 3 was presented to review the distribution of unpaved roads by ADT. It shows that the majority of unpaved roads in Wyoming have less than 100 vehicles per day.

9 Jones, Meena, and Ksaibati 8 Table 2: Unbiased Survey Results. Question Choice Comments Are there any circumstances which would justify recommending a speed limit higher that the 85th percentile? When setting speed limits to the 85th percentile, should it be the rounded down or up 85th percentile? Check the boxes of all the characteristics that would warrant a speed limit lower than the 85th percentile: If the recommended speed limit is lower than the 85 th percentile speed, check the values that can be used: Should the recommended speed limit have a minimum value that can be used? Should a ball bank test be performed on all adverse horizontal curves for unsigned roads before recommending a speed limit? Should the Average Daily Traffic (ADT) be considered for recommending speed limits? Should Average Daily Truck Traffic (ADTT) be considered for recommending speed limits? Should the segment length be considered for recommending speed limits? Should roadside clearance be considered for recommending speed limits? Should the roadway classification (ie, rural major collector, rural minor collector, and rural local road) be considered for recommending speed limits? Should the type of adjacent land-use (i.e., residential, commercial, mining, agriculture and industrial) influence the speed limit decision? Should the surface condition of the road be considered when recommending speed limits? Should the number of access points considered for recommending speed limits? Should the number of crashes on a road be used when setting speed limits? 67% - Yes, 33% - No 75% - Both should be used, 25% - rounded up N/A 67% - Yes, 33% - No 67% - Yes, 33% - No 56% - Yes, 22% - No, 11% Maybe 44% - Yes, 33% - No, 22% - Maybe 56% - No, 22% - Yes, 22% - Maybe 44% - Yes, 44% - No, 12% - Maybe 44% - Yes, 44% - No, 12% - Maybe 44% - Yes, 44% - No, 12% - Maybe 44% - Yes, 66% - No 78% - Yes, 22% - No 67% - Yes, 33% - No 78% - Yes, 22% - No When improper limits have been set and not enforced, it should be higher than the 85th percentile. Depends on roadway characteristics. Adverse horizontal curves, poor gravel condition, high number of crashes, roadside hazards, high number of access points were chosen Lower bound of pace speed (55%), Minus 5 from the 85th percentile, Minus 10 from the 85th percentile. Allowing or documenting this will most always get posted. This may lead to artificially posted speed limits. Advisory on curves that are lower than the speed limit, Consider chevrons and delineation instead. Effect of ADT is observed in the 85 th tile, As long as there is a valid sample size. Included in the 85%tile, Higher ADTT roads should generally have lower limits. Attempt should be made to reduce short speed zones Influence is seen in the 85%tile, If roadside clearance is less than 5 feet than lower the speed limit. Major roads should keep high speeds, collectors should generally have higher speeds than local roads. Influence is seen in the 85%tile, adjacent land-uses with high truck traffic should have a speed limit less than the 85th percentile Influence is seen in the 85%tile, this will take care of itself when collecting data, speed limit should be set for ideal conditions. 20 access points should warrant a reduced speed limit, influence is seen in the 85th percentile. Minus 10 mph form the 85th percentile, no lower than 30 mph Table 3: Wyoming Unpaved Road Speed Data - 82 Observations. 50 th percentile speed 85 th percentile Speed Average th Percentile Standard Deviation Deviation

10 Jones, Meena, and Ksaibati 9 Number of Roads Average Daily Traffic (vehicles/day) Figure 2: Distribution of Test Sections by ADT 82 Observations After the presentation of Wyoming unpaved road data, nine case studies were presented where each study had different characteristics associated with it. The group individually evaluated the first 2 while the next 7 were evaluated collectively. A round table discussion followed where members discussed the pros and cons of each major decision. Table 4 shows the speed data that was used for the case studies. All of the speed data was taken from actual roads in Wyoming. On average only 44% of the vehicles recorded were in the pace speed. This observation confirms that there is a higher variability in speeds on unpaved roads than on paved roads.

11 Jones, Meena, and Ksaibati 10 Table 4: Speed Data for Case Studies. Case Study/ Scenario 85th % speed 50th % speed Lower Bound of Pace (mph) Upper Bound of Pace (mph) Percentage in Pace speed % % % % % % % % % Averages % OUTCOMES OF THE FOCUS GROUP MEETING The discussions at the focus group meeting were instrumental in developing the first draft of the standards and guidelines. The group focused on four main aspects: the determination of an appropriate speed limit, data collection, roadway safety, and declaration of speed limit. For each major decision, a procedure was proposed and voted on by the group. A major concern of the group was the data collection requirements for speed data. Unpaved roads are generally very low volume roads which make some of the data collection techniques unfeasible. Data Collection A big difference for setting speed limits on unpaved surfaces compared to paved surfaces is the data collection. Most unpaved roads have very low volumes which presents challenges to the traditional spot speed study. Also, weekends can bring larger volumes and less familiar drivers onto the roads. This affects the speeds that are recorded and more importantly the safety of the road. The focus group approved data collection procedures which incorporated many of the aspects that effect unpaved roads. Procedure 1 - For the engineering studies, vehicle speeds and traffic volumes should be determined using automated traffic counters. For most low volume unpaved roads, seven consecutive days of traffic counts are required. For unpaved roads with more than 200 vehicles per day, 2 days of traffic counts may be adequate. The automated traffic count values that are required are: 85 th percentile, 50 th percentile, upper bound of the pace speed, the Average Daily Traffic (ADT) and the Average Daily Truck Traffic (ADTT). A special form was developed to assist with the collection and analysis of the traffic count data and the safety aspects of the road as shown in Table 5. The form includes five parts: general information, automated traffic count values, roadway characteristics, historical crash data, and range of speed limit values. In the form, the clear boxes correspond to the input that trained technicians or engineers are required to provide. The gray shaded boxes correspond to

12 Jones, Meena, and Ksaibati 11 the calculations and information that the registered engineer is required to provide. When collecting speed study data, the general information should be completed before proceeding to the next steps. The required automated traffic count values can be obtained from the output file that the automated traffic counters produce. As shown in Figure 3, the output file summarizes the different speed and traffic volumes that the automated traffic counters produce. Table 5: Unpaved Roads Speed Limit Data Collection Form

13 Jones, Meena, and Ksaibati 12 Figure 3: Automated Traffic Counter Output (11) Roadway characteristics are collected during a field inspection of the road. The roadway characteristics that were determined to be critical to the speed limit decision are: Roadway Length Number of Access Points Roadway Width Adjacent Land-Use Type of Terrain Roadway length was chosen so that speed zones in very short segments could not be set using the standards and guidelines. Access points is an important characteristic because unpaved roads have unplanned access points on the road that can create risk. On some unpaved roads, the roadway width is limited which can make vehicles drive on the shoulder to accommodate twoway traffic. Adjacent Land-Use was chosen to associate the roadway with a demographic of drivers. The choices for the adjacent land use are shown below and were obtained from AASHTO s Guidelines on Geometric Design for Very Low Volume Roads (12). The descriptions of each

14 Jones, Meena, and Ksaibati 13 adjacent land use highlight the type of vehicles and drivers that can be expected to traverse the road. Rural major access roads serve a dual function of providing access to abutting properties as well as providing through or connecting service between other local road or higher type facilities. Rural minor access roads serve almost exclusively to provide access to adjacent property. The length of minor access roads is typically short. Because their sole function is to provide access, such roads are used predominantly by familiar drivers. Industrial or commercial access roads serve developments that may generate a significant proportion of truck or other heavy vehicle traffic. These roads are classified separately from minor access roads, which they otherwise resemble, because of the consideration for trucks and other heavy vehicles. Recreation and scenic roads serve specialized land uses, including parks, tourist attractions, and recreation facilities, such as campsites or boat-launch ramps. Their users are often unfamiliar drivers and serve recreational vehicles including motor homes, campers, and passenger vehicles pulling boats and other trailers. Rural resource recovery roads are local roads serving logging or mining operations. Resource recovery roads are distinctly different from the other functional subclasses of very low-volume local roads in that they are used primarily by vehicles involved with the resource recovery activities and the driving population consists primarily or exclusively of professional drivers with large vehicles. Rural agriculture roads are used primarily to provide access to fields and farming operations. Vehicle types that use such roads include combines, tractors, trucks that haul agricultural products, and other large and slow-moving vehicles with unique operating characteristics. Type of terrain refers to the general character of the road. This characteristic helps look at sight distance and the alignment of the road in general terms so it can encompass the entire road. This allows the technicians or engineers to speed up the data collection process and not have to measure all of the sight distance and alignment issues. There are three different types of terrain that can be chosen: Level Highway sight distances, as governed by both horizontal and vertical restrictions, are generally long or can be made to be so without construction difficulty or major expense. Rolling Natural slopes consistently rise above and fall below the road or street grade, and occasional steep slopes offer some restriction to normal horizontal and vertical roadway alignment. Mountainous Longitudinal and transverse changes in the elevation of the ground with respect to the road or street are abrupt, and benching and side hill excavation are frequently needed to obtain acceptable horizontal and vertical alignment. (12)

15 Jones, Meena, and Ksaibati 14 Roadway Safety The focus group decided that a general road safety evaluation should be considered when determining speed limits. Such an evaluation should include the following: If there are a high number of crashes on the roadway under investigation, then a detailed crash analysis should be performed to find the causes of the crashes. Once the causes are determined, then additional steps should be taken to provide safety enhancements for high crash locations. Reducing the speed limit by itself will not automatically reduce crashes. The road should be driven at a reasonable and safe speed to determine if any curves require vehicles to slow down. Further safety enhancements such as signage, delineation, shoulder widening, and guardrails should be considered at adverse curves. When horizontal curves are signed, they should include either chevrons, delineators or curve warning signs. Speed advisory signs are not required on unpaved roads. Speed limits should not be reduced due to the presence of isolated fixed objects such as utility poles, trees, rocks or narrow cattle guards. Consideration should be given to using object markers, removing the hazard or widening the road at those locations. The speed limit should never be lowered to reduce the number of signs needed on a road. The general roadway safety section was meant to provide recommendations rather than outlining required procedures. An important decision was to not require that all curves have a ball bank test performed. It was thought that it would take too much time and effort to analyze every curve with a ball bank test. On unpaved roads, gravel buildup and constant grade changes lead to a speed that is not consistent around curves. Also trucks can travel faster around curves than smaller vehicles making the ball bank test car specific and difficult to advise a speed for all vehicles. Because of this, it was recommended to sign the adverse curves with delineators or chevrons instead of advisory speeds. It is recommended that 10 years of crash data be included in the evaluation. The following three types of crashes are evaluated: number of fatalities, number of injuries, and the number of Property Damage Only (PDO). The Equivalent Property Damage Only (EPDO) can then be calculated by using Equation 1. (Equation 1) Once the EPDO is calculated, the EPDO per mile is determined by dividing the EPDO by the roadway length. If there are a high number of crashes, then a detailed crash analysis should be performed to determine if speed is a factor in the crashes.

16 Jones, Meena, and Ksaibati 15 Determination of Appropriate Speed Limit After collecting all the required data, a registered engineer can recommend a speed limit for unpaved roads to the county commission. When recommending the speed limit, the focus group felt that the registered engineer should consider the following procedures: Procedure 2 - The preferred speed limit is the 85 th percentile speed rounded to the nearest 5 mph. Procedure 3 - A professional engineer can consider other roadway characteristics to justify a lower speed limit. But the lowest acceptable speed limit may only be up to 10 mph less than the 85 th percentile speed. Procedure 4 - The recommended speed limit on unpaved roads shall never be higher than the statutory speed limit of 55 mph Declaration of Speed Limit Form Posted speed limits (other than statutory speed limits) on unpaved roads that have been established by an engineering investigation must be documented by a Declaration of Speed Limit. A declaration of speed limit form is shown in Figure 4. When declaring a speed limit, the declaration of speed limit form must be signed and sealed by a professional engineer. The form, with appropriate background information, is then presented to the county commission where a resolution number approving the proposed speed limit is issued. The resolution number will then be added to the declaration of speed limit form. The form is then returned to appropriate county officials so that the necessary signing changes can be made. Enforcement of the new speed limit cannot occur until the appropriate signs giving notice thereof are in place. It is also recommended that copies of the resolution be sent to the local law enforcement agency(ies) for help with enforcement.

17 Jones, Meena, and Ksaibati 16 Figure 4: Declaration of Speed Limit Form FEEDBACK ON THE STANDARDS AND GUIDELINES Five different groups provided feedback on the developed standards and guidelines after the focus group meeting. They are: WYDOT Chief Engineer. Local governments attending the Transportation and Safety Congress. Wyoming Associations of County Engineers and Road Superintendents (WACERS). Wyoming County Commissioners Association (WCCA). General Public. The Chief Engineer of WYDOT wanted to make sure that the counties and commissioners had input since they were going to be the ones in charge of implementing the standards and guidelines. He also wanted the WCCA to have input on what the correct process was for declaring a speed limit. During the presentation at the WYT²/LTAP Safety Congress, it was advised that all speed limits set before the standards and guidelines were finalized could be

18 Jones, Meena, and Ksaibati 17 considered valid and wouldn t need a new study as long as they were done in accordance with WYDOT s procedures. The WACERS committee recommended that the lower bound of the recommended speed limit be changed from minus 5 mph to minus 10 mph from the rounded 85 th percentile. It was brought up to a vote and all 11 of the committee members voted for the change. The WCCA recommended that a resolution number be assigned to every new speed limit. That way if it is brought up in court they can find the resolution number and find all the supporting information that is needed. It also simplified the process of declaring a speed limit. SPEED LIMIT WORKSHOPS As part of the implementation of the standards and guidelines, the WYT²/LTAP will provide training workshops to train county technicians and engineers on how to set speed limits on unpaved roads. WYDOT worked out an agreement so that the WYT²/LTAP can establish speed limits on local roads, if the counties collect the necessary data. A workshop training manual was developed to explain all the steps and procedures in more detail. The following process is a general outline on how the Center will assist and train counties and municipalities with setting speed limits on unpaved roads: 1. Automated Traffic Counters a. The Center will provide training on the equipment and the software. b. The Center will provide training on the location and set up of the equipment. 2. Roadway Characteristics a. The Center will provide training on how to collect the roadway characteristics that are required for the study. 3. Safety Evaluation a. The Center will provide training on the safety evaluation that should take place during the speed study. This includes identifying low cost measures for improving the safety of unpaved roads. 4. Declaration of Speed Limit Form a. The Center will provide training on the steps to be taken when declaring a speed limit. This includes the required documentation and signatures. SUMMARY AND CONCLUSIONS The lack of national standards for establishing speed limits on unpaved roads proved to be a big challenge for this study. However it also provided an opportunity for Wyoming to assist other agencies that are pursuing the same type standards. The standards developed in this study can be adopted with minor modifications by any agency managing unpaved roads. The standards and guidelines for establishing speed limits on unpaved roads were developed through an extensive process that allowed all stake holders a chance to provide timely feedback. The standards and guidelines provide Wyoming counties with a step by step process and the documentation needed for establishing speed limits on unpaved roads.

19 Jones, Meena, and Ksaibati 18 According to the developed standards and procedures the following steps should be followed when establishing speed limits on unpaved roads: A registered engineer or a trained technician can collect the necessary data. For the engineering studies, vehicle speeds and traffic volumes should be determined using automated traffic counters. For most low volume unpaved roads, seven consecutive days of traffic counts are required. For unpaved roads with more than 200 vehicles per day, 2 days of traffic counts may be adequate. The automated traffic count values that are required are: 85 th percentile, 50 th percentile, upper bound of the pace speed, the Average Daily Traffic (ADT) and the Average Daily Truck Traffic (ADTT). The road should be driven at a reasonable and safe speed to determine if any curves require vehicles to slow down. Further safety enhancements such as signage, delineation, shoulder widening, and guardrails should be considered at adverse curves. Speed limits should not be reduced due to the presence of isolated fixed objects such as utility poles, trees, rocks or narrow cattle guards. Consideration should be given to using object markers, removing the hazard or widening of the road at those locations. The preferred speed limit is the 85 th percentile speed rounded to the nearest 5 mph. A professional engineer can consider other roadway characteristics to justify a lower speed limit. But the lowest acceptable speed limit may only be up to 10 mph less than the 85 th percentile speed. The recommended speed limit on unpaved roads shall never be higher than the statutory speed limit of 55 mph. The declaration of speed limit form needs to be sealed by a registered engineer then approved by the county commission with a resolution number. The training workshops will provide comprehensive knowledge to the county engineers and technicians and let them know exactly what is expected of them. It also provides an opportunity for practitioners to understand why the procedures are needed. The safety aspect of the workshop will provide an opportunity to illustrate safety tools that can be used on all county roadways. A major benefit is that the WYT²/LTAP will analyze the data free of charge if the counties collect the necessary data. This project will help create more uniform speed limits on unpaved roads and give the public confidence that they were set appropriately. The enforcement of the speed limits will be more efficient because police officers will feel that they were set appropriately and will only be ticketing the worst offenders. It will also give the enforcement and judicial system confidence that speed infractions will be upheld in the court of law. ACKNOWLEDGMENTS The authors of this paper would like to thank WYDOT, Wyoming Association of County Engineers and Road Superintendents, and the Wyoming County Commissioners Association for

20 Jones, Meena, and Ksaibati 19 their contributions in helping develop the standards and guidelines for establishing speed limits on unpaved roads.

21 Jones, Meena, and Ksaibati RITA, Bureau of Transportation Statistics. 2008, Public Road and Street Mileage in the United States by Type of Surface: Current as of January 1, (accessed July 2011) 2. Federal Highways Administration. Manual on Uniform Traffic Control Devices NCHRP, Transportation Research Board. Expert System for Recommending Speed Limits in Speed Zones. Project No. 6-67, November Dissanayake, S. Criteria for Setting Speed Limits on Gravel Roads. Journal of Transportation Engineering, ASCE, National Motorists Association. Comparison of Speed Zoning Procedures and Their Effectiveness. Report No , September (accessed June 2011) 6. Dissanayake, S. and L. Liu. Speed Limit Related Issues on Gravel Roads. Report No. K- Tran: KSU-06-5, Kansas Department of Transportation, California Department of Transportation. Traffic Operations Policy Directive. Policy No , June, Texas Department of Transportation. Procedures for Establishing Speed Zones. Manual Notice No February Vermont Local Roads Program. Setting Speed Limits, A guide for Vermont Towns. June, Wyoming Department of Transportation. WYDOT traffic studies manual JAMAR Technologies, Inc. TraxPro Program AASHTO, Guidelines for Geometric Design of Very Low-Volume Local Roads. American Association of State Highway and Transportation Officials, Washington, D.C., 2001.