Figure 1 has two line drawing perspectives showing ramp retrofits to existing entrances originally constructed with one or two steps. The first drawing shows a ramp along the building facade and parallel to it with handrails on both sides and a level landing at the top at the building entrance. Maximum ramp slope is 1:12. There are also two sets of steps down to the sidewalk from the landing. One set is parallel to the building facade at the landing at the high end of the ramp and the other at 90 degrees to the ramp and perpendicular to the facade. Both connect to the sidewalk and are protected by planters at the corners where the steps project into the sidewalk. A sidewalk width of approximately 12 feet is required for this approach. This includes a minimum 5x5-foot landing (6 feet is desirable) at the entrance, where the steps were originally located.
A similar drawing shows the addition of an entrance ramp in a narrower sidewalk. Where only 8 feet of sidewalk width is available, the parallel ramp and its landing may extend only 4 feet into the sidewalk from the building. A single set of steps runs parallel to the facade at the landing at the high end of the ramp; there is not enough sidewalk with for perpendicular steps. Part of the landing space needed to approach and open the entrance doors is recessed into the building.
Figure 2 contains two line drawing perspectives demonstrating the effects of excessive sidewalk cross slope-that is the slope of the sidewalk across its width, perpendicular to the line of travel- on pedestrians who use wheelchairs. In downhill travel, the forces of gravity tend to pull the wheelchair towards the curb. The pushing forces required to counteract these effects will be different on each wheelrim--small on the high side and large on the low side of the sidewalk. Forward momentum toward the curb may require unequal hand braking on the wheels, leading to a possible loss of control and balance. In wet or icy conditions, the pedestrian in a wheelchair may slide toward and over the curb.
In uphill travel, extra effort is required to overcome the cross slope force, effort that might otherwise be used to climb the slope. Icy or wet conditions underfoot may lead to a rearward slide, also toward the curb.
Figure 3 is a line drawing perspective illustrating the effects of compound slope on pedestrians who use wheelchairs. When travelling over a non-planar surface, such as the edge of a driveway apron where a flared side changes slope in both directions changes over a distance of only a few inches, a front caster or a rear drive wheel can lose contact with the rolling surface, which can lead to a loss of balance and control or even tipping over, if extreme.
Figure 4 is a series of line drawing perspectives showing five different sidewalk conditions at a driveway crossing.
The five different conditions shown are:
Apron Offset Sidewalk
Figure 5 is a pair of line drawing perspectives that illustrate a way of retrofitting an existing sloping driveway apron that doesn't have a level sidewalk route across it. In the `BEFORE' condition, a pedestrian using a wheelchair is shown travelling across a compound slope formed by the flares of the driveway apron with a cross slope of 1:8; arrows suggest the difficulty of the path of travel. In the `AFTER' configuration, the continuous driveway apron slope has been divided into three parts: a short segment of steeper slope (1:5), a 3-foot (minimum)-wide level passage across the driveway, and then another short segment of steeper slope (1:3). The sidewalk itself also ramps down to the level crossing of the driveway at both sides, in straight ramps with a maximum slope of 1:12.
Figure 6 is a line drawing plan that shows a sidewalk corner at an intersection. A perpendicular curb ramp, one being used by a pedestrian in a wheelchair, connects to each of the two crosswalks. A pedestrian using a white cane is at the corner between the two curb ramps. A car is shown turning the corner, which has a small curb radius of 15 feet. A larger curb radius-30 feet--is shown as a dotted line to illustrate the additional crossing distance for pedestrians that is required by larger radii.
Figure 7 is a set of three line drawing perspectives illustrating 3 types of perpendicular curb ramps. The first one is inset into the sidewalk and comprises a level landing at the top that is 36 inches--the minimum width of the curb ramp--and a minimum of 48 inches long (60 inches is desirable). The landing slope in either direction may not exceed 1:48. The ramp run may not exceed 1:12, which requires a total length of almost 8 feet where there are 6-inch curbs, since the sidewalk cross slope of 1:48 will contribute additional height as the ramp rises. Flares for ambulatory pedestrians may be as steep as 1:10, which will require a 5-foot-long taper from the toe of the ramp back up to full curb height. The line of the toe of the ramp at the street must be perpendicular to the ramp run so that both long sides of the ramp are equal in length. A diagonal ramp is shown as a perpendicular ramp installed at the apex of the corner to serve two crossings rather than one. A built-up ramp projects from the sidewalk at the curb face into the roadway and has convex flares from the ramp down to the street surface. Extra width-at least 48 inches--is preferred, since there is no edge protection from these flares. Built-up ramps are not
Figure 8 is a set of two line drawings illustrating mid-block and corner combination curb ramps. A sidewalk width of at least 6 feet is required. The sidewalk ramps down like a parallel curb ramp at a 1:12 slope to a level landing 5 feet in length. From this landing, a short perpendicular curb ramp, also at a 1:12 slope, connects to the street at the curb. Where two curb ramps are used at an intersection, it is not necessary to ramp the sidewalk back up to the original curb height as it goes around the corner; it can connect at the lower height to the second curb ramp.
Figure 9 is a line drawing illustrating a semi-projected curb ramp in perspective. It shows a perpendicular curb ramp with side flares and a top landing. The ramp run does not end at the curb, but extends across the width of the gutter, with small reverse side flares at each side. A sidewalk width of at least 8 feet is required
Figure 10 is a line drawing illustrating an intersection with 4 corners and the 3 different types of curb ramps based upon right-of-way widths: two perpendicular (to the curb face) curb ramps, one for each crossing, are shown where the right-of-way is wide enough for a landing at the top; a parallel curb ramp is shown where the right-of-way is too narrow to allow a landing at the top; and a combination ramp is shown where the sidewalk is ramped down to a somewhat lower landing from which a short perpendicular ramp connects to the street at the apex of the curve. A free right turn lane with a pedestrian island and a bulb-out (extension of the sidewalk across the parking lane) are also shown.