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Can they read your signs?
How to develop a streamlined strategy for meeting FHWA traffic sign compliance dates
Leslie McCarthy, Ph.D., P. E., Assistant Professor, and Seri Park, Ph.D., P.T.P., Assistant Professor, Villanova University, Villanova, Pennsylvania
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he Federal Highway Administration (FHWA) created minimum traffic sign retroreflectivity levels through its Manual on Uniform Traffic Control Devices (MUTCD) in response to a congressional mandate in the 1993 Department of Transportation Appropriations Act. FHWA set target deadline dates in the 2009 edition of the MUTCD for public agencies to comply with these standards. Subsequently, proposed revisions to the compliance dates were published in the Federal Register on August 30, 2011. Regardless whether the proposed revisions to the compliance dates are accepted, all public agencies must implement and continue use of a sign assessment or management method and all regulatory and warning sign retroreflectivity values must be maintained at or above the established minimum levels. These two actions must be taken within two years from the effective date of the revised 2009 MUTCD.
For a local public agency that does not formally possess a traffic sign inventory database, creating one would help ensure compliance with retroreflectivity standards. A formal sign inventory can help to reduce an agency’s risk of liability when violations or crashes occur at locations where signs are the main form of traffic control. According to the Institute of Transportation Engineers’ Traffic Sign Handbook, results from a highway tort liability study in Pennsylvania showed that sign deficiencies were cited as a leading factor in the sampled tort actions, second only to deformities in pavement surfaces. In addition, sign deficiencies were cited as the cause in 41% of crashes in which a fatality or serious injury occurred. For these reasons, it was essential that a system be developed that local public agencies can use to manage and assess their infrastructure and monitor exposure to liability.
Ideally, the basis of a sign inventory method would include data such as average daily traffic, crash details, crash locations, etc., but much of the information used in sophisticated crash analysis is not within the municipal resources to collect or is simply not available. A more realistic approach is to identify the kind of data that typical local agencies do have in proposing a method for prioritizing sign inventory assessment locations.
For most local public agencies, no overtime is budgeted for visual nighttime sign inspections. In general, assessment of signs is based on police patrols on nightly routes or on community feedback regarding signs exhibiting reduced visibility. In many cases, replacement work orders are used to address signs when budget and schedule permits. In most states, the local public agencies are faced with the challenge of having jurisdiction over the majority of traffic signs, but
An example of a traffic sign that failed retroreflectivity minimum values. All regulatory signs owned by public agencies must be maintained at or above MUTCD minimums in the near future.
little resources to manage them in a sustainable manner.
A few local public agencies in southeastern Pennsylvania volunteered to serve as the betatesters of a risk-based sign inventory strategy centered upon available resources. The three municipalities differed in characteristics such as land access and usage, centerline mileage, population, and staffing levels. Municipality 1 had a 2008 census population of 30,878 within a 13.77-square-mile area that is primarily suburban with multiple business districts and its own police department. Municipality 2 had a 2007 census population of 28,886 within a 19.8-square-mile area with similar features to Municipality 1 (including its own police department). Located in a rural setting, Municipality 3 had less than half the population over similar land area, no police department, and minimal traffic signals in its jurisdiction, relying more on traffic signs. Average daily traffic counts were not available for the majority of local roads in the jurisdictions studied; however, crash data was obtainable for all townships and the method used in the study was crash-based. Out of 2,012 reportable crashes in the three municipalities, 268 crash reports (19%) cited either a stop sign or yield sign present at the crash location.
A streamlined strategy was developed in which local public agencies can focus on each group of signs sequentially by assigning a tiered approach, capturing signs at the highest priority locations first. The local public agency would then continue collecting the next set of signs, considered to be of lessening risk, until all sign assets are recorded for a particular jurisdiction. Establishing the criteria for the tier system was done with feedback from the municipalities involved in the pilot study. It was determined that a location with three or more crashes within the previous three years is considered as a high-risk location. Properly labeling signs in the database under the designated tier allows for a sustainable asset management system. After completion of the sign inventory database, local public agencies can use a query to assess and replace all signs or other assets (e.g., degraded sign posts) that are near locations with the highest risk involved. All non-signalized intersections with three or more reportable crashes in the previous three years were identified by analyzing either State DOT or municipal crash records. These locations were observed to identify the traffic control device type and intersection type, in order to filter the crash data. For example, crashes that involved a traffic signal, flashing signal, police officer or flagman as the operating traffic control device were screened out of the process of determining Tier I locations. In addition, if a crash was coded to an Intersection Type
Lower functional class roadways encompass the majority of land access and consequently, the majority of all types of traffic signs.
Sign retroreflectivity is measured using a retroreflectometer and then numerical values are used to determine whether replacement is needed.
of “midblock” (hence, not at an intersection), then that crash site would also be screened out from the Tier I locations. The remaining data from the database was evaluated to determine all non-signalized locations with three or more crashes in the past three years.
Signs near midblock locations with three or more crashes in the previous three years were classified as Tier II. Signs at signalized intersections with three or more crashes in the previous three years were classified as Tier III locations. Only Tier I, II, and III locations would require any analysis of crash data. The remaining sign tier classifications can be developed based on engineering judgment of locations that require the most safety attention and roadway classifications. After all locations for each sign tier are established, each location can be marked on a map and regulatory and warning sign information collected. An inspection of each sign and recording other aspects such as sign post condition, sign’s distance from edge of pavement, etc., that contribute to asset management is also recommended.
For Municipality 1, the time spent implementing the streamlined strategy was continuously measured. A total of 25 hours were spent for the collection and interpretation of crash data. Field measurement of sign retroreflectivity and other sign characteristics took 15 hours. Finally, the time required to input the field data to the sign inventory (an Excel database) was 20 hours. Therefore, approximately two weeks was required to record all 90 Tier I signs for Municipality 1.
With the adjusted FHWA compliance dates approaching, employing a streamlined sign inventory strategy would provide local public agencies with a manageable approach to an otherwise overwhelming process. Although the determination of sign tiers based on crash frequency requires up-front effort, local public agencies will benefit from creating an established record of high risk locations for engineering and litigation support in the future. As with any asset management system, a sign inventory is designed to be a living tool. When new countermeasures are implemented, the previous tier rating of a sign or location must be updated according to the proposed improvements. For example, if a countermeasure changes an intersection governed by stop signs to an intersection controlled by a traffic signal, it could change the signs at this location from Tier I to Tier III or lower (depending on the new frequency of crashes). Current replacement procedures for vandalized or damaged signs should likely remain the same, but with priority placed on updating the sign inventory database after replacing, removing or installing a traffic sign.
Local public agencies that have already begun development of a sign inventory can implement a tiered strategy by analyzing crash data afterwards to determine sign prioritization ratings for each sign. It is recommended that after the development of a sign inventory, local public agencies should continue periodic surveillance of signs to observe and address factors that can affect sign retroreflectivity, including frost and dew, accumulation of dust and dirt, sign direction, graffiti, and sign post condition.
Dr. Leslie McCarthy, P.E., is an Assistant Professor in the Civil and Environmental Engineering Department at Villanova University. She conducts research on highway safety, transportation project delivery, and pavements. She worked for several
years at FHWA and administered Local Program Agency activities in partnership with FDOT. She is a licensed Professional Engineer in New Jersey and Pennsylvania. She can be reached at leslie.mccarthy@villanova. edu or (610) 519-7917.
Dr. Seri Park, P.T.P., is an Assistant Professor in the Civil and Environmental Engineering Department at Villanova University. She conducts research on highway safety, traffic impact analysis, and ITS. She worked for several years at TetraTech and taught at the University of CaliforniaIrvine. She is a licensed Professional Transportation Planner in California. She can be reached at seri.park@ villanova.edu or (610) 519-3307.
References
Carstens, R.L. “Construction and Maintenance Practices to Minimize Potential Liability of Counties for Roads in Rural Subdivisions,” ISU-ERI-Ames-82017 Project 1475. August1981. Iowa Highway Research Board.
Cunard, R. A. “Maintenance Management of Street and Highway Signs,” National Cooperative Highway Research Program Synthesis Report 157. September 1990. Transportation Research Board of the National Academies.
Hildebrand, E.D. “Reductions in Traffic Sign Retroreflectivity Caused by Frost and Dew,” Transportation Research Record No. 1844. December 2003. pp. 79-84. Transportation Research Board of the National Academies.
Kirk, A. R., E. A. Hunt, and E. W. Brooks. “Factors Affecting Sign Retroreflectivity,” Report No. ORRD-01-09. January 2001. Oregon Department of Transportation.
Manual of Uniform Traffic Control Devices (MUTCD), Federal Highway Administration, December 2009. 2009 Edition. Page I-4.
“National Standards for Traffic Control Devices; the Manual on Uniform Traffic Control Devices for Streets and Highways; Revision,” Federal Register. August 31, 2011. Volume 76, Number 169. Pages 54156-54162.
Vereen S., J. E. Hummer, and W. Rasdorf. “A Sign Inventory Study to Assess and Control Liability and Cost,” Report No. FHWA/NC/2002017. August 2002. North Carolina State University.
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