In general, accessible design requires the elimination of obstacles within the route of travel, 0.9 m minimum width of travel route, 1.5 m passing areas every 60 m on accessible routes less that 1.5 m in width, maximum grade of 1:20, steeper grades of up to 1:12 may have ramps and 1.5 m level landing areas for every 0.8 m in elevations change along 1:12 ramps.
A marked crosswalk includes the use of pavement markings and either signs or signals. Pavement markings should not be used alone to indicate a pedestrian crossing, and signs should be supplemented by pavement markings. Crosswalk signs should not be where pedestrian or full vehicle signals are in place (MoTh, 94, 1-3). Stop bars, or twin lines for pedestrian crossings, are suitable only where the approach is controlled by means of a signal or stop sign. Zebra markings are recommended where there are no signal controls as they are more visible to drivers. The length of the zebra stripe differs according to traffic speed (3.0 m where speed is 60 km/h or less, 4.0 where speed is 70 km/h and greater.
Special crosswalks include pavement markings, internally illuminated overhead signs, down lighting of crosswalk, push buttons, timers, and overhead flashing beacons. These devices can be used in combination to make a crosswalk safer and more effective. Where traffic speeds and volumes are very high, grade separated crossings provide the best protection and ease in crossing to pedestrians.
Curbs are useful to provide a physical separation between pedestrians and traffic. They stop vehicles from mounting the curb for parking, and the gutter acts as a path for storm water drainage. In rural areas, a curb may seem too urban, and a ditch or swales provide separation. An extruded (asphalt) curb is not recommended where there are bicycle lanes, and may interfere with drainage. Raised pavement markings are strongly discouraged as a hazard for cyclists.
Drainage Grates are best if located outside the route of pedestrian travel, if not possible, the openings should be less than 13 mm in width and should be mounted flush with the surrounding sidewalk surface.
In steep areas, continuous handrails are to be provided at a height of 865 to 920 mm to help people in danger of slipping and falling.
An accessible route of travel should not exceed a grade of 1:20 or 5 percent. If the grade must exceed this maximum, a ramp of not greater than 1:12 or 8.33 percent may be constructed. Landings of 1.5 metres in length are required for every 9.1 metres of vertical height and must have handrails and railings. There are exceptions where the distance is minimal, though a slope of greater than 12 percent is difficult for many users.
Building Access Handbook: 1998.
The minimum acceptable width for sidewalks is 1.5 metres on local streets and 1.8 metres elsewhere, and wider where there are greater numbers of pedestrians. Where a walkway is less than 1.5 metres wide, passing areas must be installed. Vertical clearance must be a minimum of 2 metres, AASHTO recommends a minimum of 2.4 metres. A cross slope must not be greater than 2 percent but must allow for adequate drainage. Sidewalks must not tilt where driveways cross the street as this adds difficulty to walking for people who may be mobility impaired. There are acceptable designs requiring an extension of a level sidewalk into the driveway; dipping the entire sidewalk where crossed by a driveway may result in drainage problems and add complications to sidewalk travel.
Sidewalk Ramps (Curb Cuts)
Ramps are useful for all people, baby strollers, luggage wheels, in-line skaters, bicyclists, and people in wheelchairs. They provide accessibility at intersections, building entrances, and other areas where elevated walkways are edged with curbing. It is recommended that curb ramps have a detectable warning surface for people who are visually impaired. A warning surface is required at transit ramps. Ramps must be included on two sides of a corner to point pedestrians across to the other curb and must be 0.9 metres wide with a maximum grade of 1:12 and 1:10 on side aprons. Curb cuts for multi-use paths should be the full width of the pathway.
Street furniture signs, trash cans, and utility boxes may pose hazards to the visually impaired person. In general, it is suggested that street furniture be grouped together to be more noticeable than they would individually and take up less room. Add contrast with a brighter color, maintain a clear height of pedestrian walkways, and place grouped objects in an area with a different surface, and/or mark with a tactile strip.
A minimum planting strip is about six feet in width from the edge of the curb to the edge of the sidewalk. This provides adequate space for the tree to develop, although as little as four feet may be adequate. Trees may be planted in 20, 30, 40 or 50-foot intervals and should form a canopy overhead. Trimming trees to about 9 feet in height preserves sight lines for drivers and pedestrians. Tree species should be carefully chosen for good performance.
Potential hazards from tree roots can be controlled by laying a good base of crushed gravel above the tree roots and below concrete sidewalks so they can grow without causing cracks in the sidewalk. (Scott 41). Tree roots that may be a hazard to pedestrians can be painted yellow as a warning.
Smooth surfaces such as cement concrete or asphalt are firm and stable enough to support wheelchair wheels, crutch tips, and other mobility aids. Smoothed gravel screenings may be acceptable in recreational settings, however loose gravel and wood chips generally do not provide for an accessible surface.