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Traffic Monitoring in Recreational Areas
A Successful Practitioner's Handbook

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Executive Summary

Traffic monitoring in recreational areas is often challenged by distinct traffic and roadway characteristics and the multitude of agencies responsible for the management of Federal lands and/or the collection of supporting traffic data. These challenges are exacerbated by a lack of consistent procedural guidance; existing national traffic monitoring guidelines lack sufficient direction and detail for recreational travel.

In an effort to improve/lend consistency to traffic monitoring in recreational areas, the Coordinated Technology Implementation Program tasked the Office of Federal Lands Highway-Federal Highway Administration (FHWA) with conducting an assessment of the nationwide practices for recreational traffic data collection. This work was performed by the Texas Transportation Institute and Chaparral Systems, Inc., under contract to Battelle.

There were three primary tasks:

  1. a review of pertinent literature related to recreational traffic data collection
  2. a targeted survey of various State and local agencies responsible for traffic monitoring
  3. the conduct of a workshop focused on traffic monitoring in recreational areas.

Key findings from these activities are briefly described below and are related to: national guidance for traffic monitoring in recreational areas, vehicle classification, recreational traffic monitoring as described in the literature, and recreational traffic monitoring as observed in practice.

National Guidance for Traffic Monitoring in Recreational Areas

Current national traffic monitoring guidance documents - including the Traffic Monitoring Guide, 1 Guidelines for Traffic Data Programs, 2 and the Highway Performance Monitoring System Field Manual for the Continuing Analytical and Statistical Database 3 - recommend a traffic monitoring framework that comprises: (1) a modest number of permanent continuous monitoring locations that adequately characterize the variation of traffic by day of the week and month/season of the year, and (2) a large number of portable short-term (typically 24 to 72 hours) monitoring locations that can support determination of "annualized" estimates using monthly/seasonal and day- of-week adjustment factors derived from the permanent continuous monitoring locations.

Recreational traffic can vary greatly by day of the week and month of the year, challenging the calculation of seasonal and day-of-week adjustment factors. National guidance documents recognize recreational traffic monitoring challenges but provide little substantial guidance to address them. Existing national guidance documents focus attention on major commuting and through- traffic routes because: (1) recreational traffic has greater variability and specific procedures for monitoring it are less formulaic on a national basis, and (2) recreational traffic comprises a small percentage of the total vehicle-miles traveled that must be monitored by resource-constrained State agencies. Consequently, most State Departments of Transportation (DOTs) focus traffic monitoring efforts on high-volume, high-mileage roadway classes that more significantly impact Federal- aid apportionment.

For these documents to have utility for traffic monitoring in recreational areas, additional detail and direction is required. This amendment process is not uncommon for Federal lands; distinct roadway design criteria and aesthetic guidelines have been previously developed in place of or as a supplement to more generalized national guidance.

Vehicle Classification

Recreational traffic is distinct with respect to the types of vehicles in the traffic stream; recreational traffic generally comprises a higher proportion of recreational vehicles (RVs), buses, and vehicles pulling trailers. The proliferation of various vehicle classes (the variety of which depends on the season and Federal Land unit) suggests that the commonly used FHWA vehicle classification scheme is insufficient in adequately characterizing recreational traffic. Under the FHWA vehicle classification scheme, the types of vehicles and vehicle combinations that frequent recreational areas are aggregated with other passenger cars, buses, and trucks across 6 of the 13 possible vehicle classifications.

Alternative vehicle classification schemes better distinguish the types of vehicles and vehicle combinations that frequent recreational areas from the general traffic. For example, the American Association of State Highway and Transportation Officials (AASHTO) defines 19 different vehicle classes for calculating design dimensions for the geometric design of roadways, intersections, and interchanges. 4 Similarly, the Highway Capacity Manual distinguishes passenger cars, trucks, buses, and recreational vehicles when calculating the effect of various vehicle types on the capacity of roadways, intersections, and interchanges. 5 National safety databases, such as the Fatal Accident Reporting System, include van-based or pickup-based motor home, medium/heavy truck based motor home, and camper or motor home-unknown truck type among other vehicle types. 6 Looking outside the United States, the Province of Alberta in Canada uses a vehicle classification system consisting of five classes including recreational vehicles. 7 Most directly reflecting the types of vehicles and vehicle combinations that frequent recreational areas, the National Park Service (NPS) developed a unique vehicle classification scheme that consists of eight vehicle types: motorcycles, passenger cars, RVs, vehicles pulling trailers (including RVs), transit/shuttle buses, tour buses, light-duty trucks, and heavy-duty trucks. 8

Automated methods for data capture have been developed largely around the FHWA vehicle classification scheme. A noted challenge is the accurate classification of individual vehicles across the 13 categories when similarities exist in the number of axles (i.e., a passenger car pulling a camper trailer may be misclassified as a four-axle single-unit or single trailer truck). Alternatives to axle- based data capture mechanisms are currently focused on vehicle length and vehicle profile. The Minnesota DOT has initiated a pooled- fund study that will investigate issues related to length-based vehicle classification. 9 The Province of British Columbia in Canada uses a length-based vehicle classification system similar to the one proposed here. Perhaps more appropriate for distinguishing the types of vehicles and vehicle combinations that frequent recreational areas are automated systems that capture the full vehicle profile. A variety of profiler systems are available commercially. Technology costs increase with sophistication and performance; traffic monitoring agencies must reconcile these added costs with the perceived value of accurate vehicle classification data for recreational areas.

Recreational Traffic Monitoring as Described in the Literature

Not surprisingly, researchers observed a disproportionate focus on traffic monitoring in urban rather than recreational areas in the published literature. Publications that did address recreational traffic monitoring generally considered: (1) the use of recreational and/or seasonal factor groups, (2) methods to support determination of recreational and/or seasonal factor groups, and (3) the likely errors associated with factoring or annualizing short-term counts on roads with high-variability traffic.

In general, a review of the literature confirmed that a number of traffic monitoring agencies in the United States and Canada are currently using one or more recreational factor groups. Recommended methods to improve upon factor group determination considered the use of the coefficient of variation, cluster analysis, plots of monthly traffic factors, and geographic mapping of continuous count sites. In one study, traffic monitoring agencies were encouraged to focus on accurately assigning short-term counts to factor groups, rather than on conducting longer duration counts (e.g., 72-hour counts). Based upon observed estimation errors, proposed alternatives to the traditional factor approach included regression analysis and artificial neural networks; however, mixed results in improving average annual daily traffic estimates were reported.

Recreational Traffic Monitoring as Observed in Practice

Additional information regarding traffic monitoring in recreation lands at Federal, State, and local levels was gathered through a targeted survey of State and local agencies and the conduct of a recreational traffic monitoring workshop.

Targeted Survey of State and Local Agencies

A targeted survey of ten State DOTs (Colorado, Florida, Idaho, Indiana, Missouri, Nevada, New Jersey, Utah, Wisconsin, and Wyoming) and three metropolitan planning organizations (Metropolitan Transportation Commission - San Francisco Bay Area, Metroplan Orlando, and Southwest Missouri Council of Governments) was conducted as part of this investigation. Survey participants were asked to respond to a series of questions related to: their agency's conduct of continuous traffic counts; the number of automatic traffic recorders (ATRs) and automatic vehicle classifiers used for recreational and non-recreational traffic data collection; the nature and extent of any recreational, seasonal, or daily factor groups in use; and the nature and extent of roadway mileage under the agency's jurisdiction.

Nearly all of the participating State DOTs maintain one or more seasonal factor groups for recreational traffic monitoring. Several States that have distinct winter and summer recreational traffic maintain two factor groups. The Florida DOT reported using more than two recreational traffic factor groups while the Indiana DOT reported using no factor group for recreational traffic.

None of the planning agencies that were contacted indicated that they routinely monitor recreational traffic; instead, planning agencies rely upon their respective State DOTs to collect this data. Planning agencies may occasionally collect data in recreational areas to support planning uses, but this is done as part of a "special studies" process.

Recreational Traffic Monitoring Workshop

The purpose of the workshop was to bring together State and Federal land agencies to discuss current and preferred practices for monitoring traffic in recreational areas and to identify opportunities for improving traffic monitoring to and within Federal lands. Representatives from each of the participating Federal, State, and Provincial agencies described specific traffic monitoring practices related to: the use of supporting traffic data collection technologies; the conduct of short- duration counts; the use and characteristics of recreational or seasonal factor groups; vehicle classification; and traffic data use, quality, reporting, and sharing. In addition, participants collectively identified broader challenges related to traffic monitoring in recreational areas. Key findings are summarized below:

  • Use of combined permanent and portable counters for data collection was generally reported, but differences in the number of sites used, the subsequent geographic coverage, and the types of technologies were observed.
  • Vehicle classification data is not routinely collected; participants cited challenges related to technological limitations, inadequate recreational road geometry/structure, difficulties in annualizing vehicle classification counts based on short-duration counts, and a lack of consensus among State and Federal agencies regarding the value of vehicle classification data compared to the additional costs of equipment, installation, and data processing.
  • Short-duration counts are commonly conducted: in 48-hour durations, on Tuesday through Thursday, once every 2 or 3 years. They are often scheduled: in the same month each year at a given site; during different months per site annually by design to account for seasonal variability and/or to verify and refine factor groups; or as scheduling or weather permits. Exceptions include the Nevada DOT, which conducts 7-day counts on an annual basis to account for unique recreational traffic patterns, and the Washington State DOT and Manitoba Infrastructure and Transportation, which conduct 48-hour counts twice per year in recreational areas.
  • Factor groups in use by participating agencies - differing in both number and characteristics - are often assigned on the basis of: roadway functional class, traffic composition, travel patterns, proximate/destination land use, climatic region, relative importance for capturing recreational trips, and/or resources/ costs. Resources/costs are supported by (in order of preference): data from proximate ATRs, cluster analysis, and/ or knowledge of the area/professional judgment.
  • The motivation for collecting traffic data was to: meet ongoing Federal reporting requirements; support decision-making related to safety concerns; obtain estimates of demand (i.e., visitation) for comparison with supply inventories, economic assessment and/or determination of resource impact; support decision-making related to system design, maintenance, and management; and/or support determination of cost allocations under cost sharing arrangements.
  • Neither existing data quality nor the data quality requirements were able to be effectively described for participating agencies.
  • Over time, the reporting of traffic data has migrated from published annual reports to the Internet, providing timely on-line access to data; however, associated modest concerns over the potential for liability have been raised.
  • Data sharing is variable but generally limited among participating agencies. Data sharing opportunities between the FHWA Office of Highway Policy Information and the Office of Federal Lands Highway were identified and appear promising.
Broader Traffic Monitoring Challenges

In addition to these practice-specific observations, a number of overarching challenges to traffic monitoring in recreational areas were identified. These challenges generally relate to: differing organizational structures and priorities among agencies related to the importance placed on recreational areas and the traffic monitoring function; funding and resource constraints and associated difficulties in replacing staff and technology assets; and the unique aesthetic, cultural, and environmental considerations in recreational areas.

Next Steps

Two fundamental opportunities emerged as a result of this investigation related to:

  1. resource and data sharing
  2. the pivotal role of FHWA's Office of Federal Lands Highway in improving/ lending consistency to traffic monitoring in recreational lands.

In the short-term, opportunities exist to share both resources and data among agencies responsible for recreational traffic monitoring. For longer-term efforts, FHWA's Office of Federal Lands Highway should play a key role in facilitating and supporting improvements to recreational traffic monitoring among diverse partners.

Through this investigation, the unique characteristics of participating agencies and the respective lands under their jurisdiction became evident. Despite the motivation towards more consistent recreational traffic monitoring, any proposed changes to existing practices cannot be a "one size fits all" approach. It must remain flexible to address the respective differences in underlying mission and priorities and the nature and extent of their jurisdictional land areas and associated roadway network among agencies tasked with managing recreational areas.

 

Footnotes

1. Traffic Monitoring Guide. FHWA-PL-01-021. Office of Highway Policy Information, Federal Highway Administration, U.S. Department of Transportation. Washington D.C. May 2001.

2. Guidelines for Traffic Data Programs. American Association of State highway and Transportation Officials. Washington D.C. 1992.

3. Highway Performance Monitoring System Field Manual for the Continuing Analytical and Statistical Database. Office of Highway Policy Information, Federal Highway Administration, U.S. Department of Transportation. Washington D.C. May 2005.

4. AASHTO Green Book - A Policy on Geometric Design of Highways and Streets, 5th Edition. American Association of State and Highway Transportation Officials. November 2004.

5. Highway Capacity Manual. Transportation Research Board, National Research Council. Washington D.C. 2000.

6. https://www-fars.nhtsa.dot.gov/Vehicles/VehiclesAllVehicles.aspx, accessed December 17, 2008.

7. Clayton, Alan, Jeannette Montufar, Dan Middleton, and Bill McCauley. Feasibility of a New Vehicle Classification System for Canada. North American Travel Monitoring Exhibition and Conference (NATMEC). August 2000.

8. National Park Service. Traffic Data Report. 2004.

9. https://www.pooledfund.org/projectdetails.asp?id=416&status=4, accessed December 18, 2008.

 

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