When pedestrian facilities are to be constructed or reconstructed as part of project plans, the facilities should be designed to accommodate the disabled. Guidance in design of pedestrian facilities with access for the disabled is available (Ref. 11).

Walks. Walks should be provided in urban areas where pedestrian traffic currently exists or is planned in the future. Walks may be provided in rural areas where they will have sufficient use in relation to cost and safety. Walks are usually made of concrete, although asphalt or gravel may be used under special circumstances. Concrete walks are usually 4 in (100 mm) thick. At drive locations, the thickness is increased to 6 in (150 mm), or the drive thickness, whichever is greater. Asphalt or gravel walks are mostly used in parks, rest areas, etc., where there is low usage. Asphalt walks consist of 2 in (50 mm) of asphalt and 5 in (250 mm) aggregate base, while gravel walks are con­structed of 4 in (100 mm) compacted aggregate base.

Walk Design. The normal width of walks is 4 ft (1.2 m) for residential areas and 6 ft (1.8 m) for commercial areas or major school routes. In downtown areas, the walk width normally extends from the curb to the right-of-way or building line. Transverse slopes should be 1/4 in/ft (21 mm/m). The grade of the walk is normally parallel to the curb or pavement grade, but may be independent. The walk and the “tree lawn” (see next section) normally slope toward the pavement. Care should be taken in setting the pavement curb grade so that the sidewalk and the curb will not trap water or otherwise preclude usability of the adjoining property. The back edge of the walk should be located 2 ft (0.6 m) inside the right-of-way line, unless grading, utilities, or other considera­tions require a greater dimension.

Tree Lawn. The tree lawn is defined as the area between the front of the curb and the front edge of the sidewalk. Grass is usually provided in the tree lawn, although in some urban areas the tree lawn is paved. As shown in Fig. 2.30, in most cases, the desirable tree lawn width is 8 ft (2.4 m) or more. The 8-ft (2.4 m) width provides an area for snow storage and for traffic signs, and an adequate distance for elevation changes at drives. Tree lawn widths of less than 5 ft (1.5 m) result in locating of sign­posts close to pedestrians using the walk, and steep grades on drive profiles. The mini­mum tree lawn width is 2 ft (0.6 m).

Border Area. In an urban area where a walk is not provided, the area between the face of curb and the right-of-way line is often referred to as a border. As indicated in Fig. 2.30d, the border width in residential areas should be at least 8 ft (2.4 m) and preferably 14 ft (4.3 m). In commercial areas, the minimum border width is 10 ft (3.0 m), while a 16-ft (4.9-m) width is preferable.

Walks on Bridges. Walks should be provided on bridges located in urban or suburban areas having curbed sections under two conditions: (1) where there are existing walks on the bridge and/or bridge approaches, or (2) where evidence can be shown through local planning processes, or similar justification, that walks will be required in the near future (5 to 10 years). Anticipated pedestrian volumes of 50 per day justify a walk on one side, and 100 per day justify walks on both sides. Walks on bridges should preferably be 6 ft (1.8 m) wide in residential areas and 8 ft (2.4 m) wide in commercial areas measured from the face of curb to face of parapet. Widths, however, may be as much as 12 ft (3.7 m) in downtown areas. The minimum bridge walk width is 5 ft (1.5 m).

Walks under Bridges. The criterion for providing walks at underpasses is basi­cally the same as described above for walks on bridges. An exception is that in areas where there are no approach walks, space will be provided for future walks but walks will not be constructed with the project unless there is substantial con­current approach walk construction. Where the approach walks at underpasses include a tree lawn, the tree lawn width may be carried through the underpass wherever space permits.

Curb Ramps. A curb ramp is a portion of the walk that is modified to provide a gradual elevation transition through the face of the adjoining curb. It is designed to provide safe and convenient curb crossings for the disabled in wheelchairs, but it can also be used by others. Examples include wheeled vehicles maneuvered by pedestrians and bikeway traffic, when such use is permitted. Curb ramps should be provided where curb and walks are being constructed at intersections and other major points of pedestrian curb crossing such as mid-block crosswalks. When a curb ramp is built on one side of a street, a companion curb ramp is required on the opposite side of the street. The basic requirement is that a crosswalk must be accessible via curb ramps at both ends, not one end only. In most cases, curb ramps will be installed in all quadrants of an intersection. Curb ramps should be located within crosswalk markings to permit legal street crossings. The ramp location must be coordinated with drainage structures, utility poles, etc. The normal gutter profile should be continued through the ramp area, except the profile may be altered to avoid a location conflict between the ramp and a drainage structure. Drainage structures should not be located in the ramp or in front of the ramp. Catch basins should be placed upstream from the ramp.