Stabilized Engineered Wood Fiber for Accessible Trails

Acceptable Trail Surfacing Requirements

Current trail design considerations include quantity of traffic and type of use, such as walking and wheelchair use, biking, horse riding, and other allowed uses. Trail surfaces are currently considered accessible only if the surfacing material is firm, stable, and slip-resistant and the trail has the engineered attributes of adequate width, moderately short slopes, passing spaces, and appropriate signage. A traditional paving material such as asphalt and concrete may be appropriate, but this type of surface is expensive to construct, requires the use of heavy materials and equipment, and may detract from the aesthetics of the trail.

The Americans with Disabilities Act (ADA 1990) states that accessible surfaces shall be stable, firm, and slip-resistant. These three criteria have not been defined adequately within the ADA Accessibility Guidelines for quantitative measurement on any specific surface. Currently, the only objective method that is suitable for assessing the firmness and stability of playground surfacing systems is the rotational penetrometer (Axelson and Chesney 1999).

As when constructing trails with native soils, it is very desirable to drain water quickly away from the surface of a SEWF trail. This is critical in maintaining the stability of native soils and for reducing the biodeterioration potential of a wood fiber based surface. Keeping water off the surface also maintains adequate friction on the stabilized EWF during sub-freezing temperatures. The rotational penetrometer, a portable measurement device that simulates a wheelchair caster negotiating the test surface, was used to assess the level of accessibility.

We also needed to consider several practical aspects for processing the SEWF material and maintaining a safe work environment. Based on our experience in field applications, stabilizing binders needed to be applied on site or mixed with the EWF no longer than 1 h prior to placement on the ground surface. The practical considerations were (a) cure/set time prior to surface use, (b) range of EWF moisture and temperature conditions acceptable for use, (c) emission of fumes or odors, workable exotherms, and toxic or other chemical release/concerns from the binder/ EWF mixture, and (d) deleterious effects of SEWF on trail users.