The Shared Use Path Concept and the Olympic Discovery Trail
Over the last two decades, transportation planners and recreation managers have come to recognize a category of non-motorized multi-user transportation/recreation pathways that serve a wider variety of users and transportation modes than the traditional recreational trail category. This type of pathway, often termed a "shared use pathway", requires a different set of design criteria to ensure the safety and enjoyment of the diverse user communities it serves. A shared use path is designed to accommodate a wide range of non-motorized users, including pedestrians, cyclists, rollerbladers, skateboarders, equestrians, and mobility impaired users with mobility devices. A shared use path serves a transportation function, such as bicycle tours and commuters, as well as a recreational one. Shared use pathways require a surface which is wider, lower in gradient, and smoother than that commonly associated with a recreational trail. They also require a firm stable slip-resistant surface.
The Olympic Discovery Trail (ODT) is a shared use path. The basic concept of the ODT is a 120+ mile non-motorized route from Puget Sound (Port Townsend) to the Pacific (La Push) that links the population centers of the North Olympic Peninsula. The ODT has always embraced and designed for a wide user community, including road cyclists, mountain bikers, pedestrians, equestrians, mobility impaired users, and others. The ODT route passes through numerous jurisdictions: tribal, federal, state, county, and city, who are the underlying owners of the trail segments.
Shared Use Path Standards
American Association of State Highway and Transportation Officials (AASHTO)
The Shared Use Path concept and pathway category has been developed primarily within the transportation sector, as opposed to the recreation sector. As a result, the only widely accepted source of design standards for shared use pathways have been those developed by AASHTO. The AASHTO Guide for Development of Bicycle Facilities was first published in 1981 and was updated in 1999 and 2010 (draft). This publication provides guidance on the design, maintenance, and operation of bicycle facilities, including shared use pathways such as ODT. The AASHTO standards are developed to insure BOTH the safety of all pathway users AND compliance with the requirements of the ADA for mobility impaired users. The AASHTO design standards are (almost) universally accepted by transportation planners and form the basis for shared use pathway design standards in most states, counties, and cities throughout the US.
One of the unique characteristics of Shared Use Paths that impacts standards is the very wide range of speeds characteristic of user classes. Speed ratios of 4-5 to 1 are common (i.e. between walkers and bicycles) and result in significantly more passing from behind than on roadways. Path widths must accommodate walkers on shared use paths, who frequently prefer to walk side by side, while providing for safe passing by bicycles. Standard widths are 12 feet in congested areas, 10 feet under normal use, and, rarely, 8 feet in very low use areas. All widths require two foot clear shoulders on both sides. Frequently, one of the shoulders is widened to four feet to accommodate equestrian traffic in areas where it is appropriate to include that user group. Other standards include slope less than 5% (preferred), but not more than 8% (maximum sustained slope). Separation from roadways requires a minimum 5 foot, non-paved, separator unless a barrier is provided. Asphalt paving supports the widest range of user groups. Compacted rock crusher fines can be substituted, but are undesirable for small wheels (mobility devices for the disabled, roller blades) and slippery for bicycles on down grades. Other standards include trail bed construction, drainage, overhead clearance, turn radii, sight lines, barriers on side slopes, and safety signs and markings.