National Trail Surfaces Study

I. Introduction to the Study

Purpose

For many years, the National Center on Accessibility (NCA) at Indiana University received questions from organizations, agencies and individuals on how to make natural surface trails firm and stable. The inquires centered on what materials would provide a firm and stable surface so people with disabilities could have a quality trail experience AND would blend in with and be friendly to the environment. In 2004, the National Center on Accessibility initiated a research study of trail surfaces funded by the U.S. Access Board. The longitudinal study objective was to evaluate the ability of a variety of aggregate and organic or natural by-product soil stabilizer trail surface materials to meet firmness and stability accessibility guidelines over a five-year period of use (data were collected over 51 months).

Background

June 20, 2007, the Access Board issued proposed guidelines for outdoor developed areas that include requirements for newly constructed or altered trails. Technical requirements for trails include the provision that trails that are accessible meet firmness and stability guidelines. Advisory information in the guidelines discusses the use of a Rotational Penetrometer to measure the firmness and stability of surfaces that are located on trails. According to U.S. Access Board Notice of Proposed Rulemaking (NPRM) for Outdoor Developed Areas contained in the June 20, 2007 Federal Register, firmness is defined as “the degree of surface resistance to deformation, especially by indentation or the movement of objects;” stability is defined as “the degree to which a surface resists change from contaminants or applied force, so that when the contaminant or force is removed, the surface returns to its original condition.” The proposed guidelines provided a table in an advisory that listed the firmness and stability classifications and their respective amounts of penetration calculated in inches (Table 3). These calculations were based on the findings of a small research project on firm and stable exterior surfaces conducted for the U.S. Access Board by Beneficial Designs in 1999.

The means and materials used to establish firm and stable exterior surfaces are diverse. Crushed stone, fines, packed soil, and other natural materials can provide a firm and stable surface. Natural materials bonded with synthetic materials are also hypothesized to provide the required degree of stability and firmness” (Final Report, US Access Board's Regulatory Negotiating Committee, 1999).

In the past, there have been a number of studies that have examined alternatives to asphalt and concrete as suitable materials for making trails accessible to people with disabilities. Most notably, the USDA Forest Service and the U.S. Department of Transportation/Federal Highway Administration have for years been conducting research on various stabilizers and other products as possible uses for trail stabilization. The overall objective of the NCA Trail Surface study was to contribute to the existing body of knowledge to determine which combination of stabilizer materials and aggregates provide the most firm and stable pedestrian use trail in different environments, climates and regions.

Modifications to the Longitudinal Study

In 2006, NCA began the recruitment of various sites to participate in the original study objectives. Entities such as the National Park Service, US Forest Service, and city Parks and Recreation departments were the central focus of the recruitment process. By the end of 2006, NCA had initial commitments from a number of state or federal outdoor recreation entities to provide test sites for the trail surface study, however, the down turn in the economy and additional factors such as lack of ability to commit labor hours and installation resources, resulted in those commitments being withdrawn. From the perspective of the individual potential sites, the original study objectives and methods for achieving them relied heavily on their ability to contribute their own money and labor to the study procedures; both resources that we saw become quickly depleted and/or significantly diminish. Potential study participants expressed concern in the ability to fund the portions of the study previously agree to be financially responsible for, which included the aggregate material needed for both the base of the trail surface and the aggregate which was mixed with the stabilizer for the cases where necessary. Soon after the initial concerns were being expressed by potential participants, NCA began receiving notifications that due to economic hardships, potential test site staff were being let go, and therefore the labor required in the study parameters to install the surfaces, and to maintain and observe them, disappeared. Another difficulty the potential test site location had was the ability to maintain the trails surface study site through the proposed five-year period of time. Most entities felt the timeframe was too long, and while they understood the need for the longevity in terms of receiving the most accurate data on the surface, it was not within their capability to meet those parameters. NCA received letters that cited these difficulties in addition to others. Financial restraints were not the only obstacle NCA faced in the beginning phases of the study. It was also difficult navigating through the research process of the National Parks Service, which is where a lot of the study energy was initially invested in gaining participation for the study. While many parks agreed to the study, and even got so far as to identify installation locations, the process of applying for in-the-park research from an outside agency made it impossible in some parks for the study to move forward. It became apparent that conducting the installation, maintenance, monitoring, and data collection at locations throughout the country was not feasible at that current time. As a result, the longitudinal data collected and reported for Part I of this study over 51 months, is limited to the Bradford Woods site in Martinsville, Indiana. The scope of the study again changed course to continue to discover other methods of contributing to the research on firm and stable natural trail surface alternative. The results of the change in scope is discussed in Part II of this report.