E 592 Design Standards (formerly 532.2)

Design elements to be considered include the following: location, slope of ramp and sides, width, curb face (lip), construction material, and surface texture.

E 592.1 Location Of Access Ramps

Access ramps should be located to be safe for the people using them. The ramp should be within the limits of existing or proposed crosswalks.  Coordination with the Department of Transportation may be required to assure compatibility between the ramps and crosswalks.

E 592.11 Access Ramps at the MC

An access ramp at the MC, as illustrated on Figure E 632.211A is preferred for the following reasons:

1. This location permits the construction of a single ramp to serve two crosswalks.
2. The area is generally clear of utilities.

A safe refuge should be provided at the foot of the ramp to avoid forcing people in wheelchairs into the path of moving vehicles.  A refuge is particularly important where the crosswalks are marked, and traffic is using the curb lane.

The area available for refuge is dependent on the curb radius and the delta angle and whether the crosswalk lines are offset from the curb lines produced.  The amount of refuge is characterized by a distance, M, measured along a radial from the curb line to the intersection of the crosswalk lines.  M should be a minimum of 3 feet.

The Department of Transportation prefers that the crosswalk be offset 3 feet back of the curb lines produced. With the usual 3-foot crosswalk offset, a minimum curb radius of 17.5 feet would be needed when the delta is close to 90°.  Where the normal 25 foot curb radius is used on adequate refuge can be provided where the delta is greater than 77°.  Sufficient M could be obtained by increasing the curb radius or securing Department of Transportation approval for a lesser crosswalk offset.  The M available by various combinations of crosswalk offset, curb radius and delta are given in Figure E 632.211B.

Refuge areas are of little importance where there are no painted crosswalks and traffic is light, such as generally the situation in single family and rural areas.

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E 592.12 Access Ramps at or near the BCR

Access ramps at or near the BCR should be used only if it is not possible to place a ramp at the MC. The three types (A, B, and C) shown in Figure E 632.212 illustrate the variations in location.  The ramps can be used individually or in any combination. However, a minimum of 6 feet of full height curb should be provided between ramps for safety and aesthetic reasons.  Following are reasons why this location is not preferred:

1. A ramp at any of these locations can serve only one crosswalk.
2. These locations do not provide the uniformity desirable for a person with low or no vision.
3. Type B location is generally occupied by traffic signals, streetlights, fire hydrants, catch basins, power poles, etc.
4. Type B location would usually require relocation of the crosswalk.

Reasons why these locations might be appropriate include the following:

1. These locations are applicable when the return has an insufficient delta angle to provide a refuge area required for an MC location.
2. Type C location is preferred when only one ramp is required because pedestrian crossings in the other direction are restricted or not desirable.
3. Type B locations can be used in pairs without regard to curb return radius or delta.
4. Type B locations leave full height curb in return for the benefit of people who have low or no vision.

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E 592.13 Access Ramps at Other Locations

Ramps shall be provided at mid-block crosswalk and crosswalks at jogged intersections.  Ramps shall also be provided at curbed driveway entrances to private property and at alley intersections where a curb face is maintained across the sidewalk area.  See Figure E 632.213.

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E 592.2 Slopes

Ramp Slope - A ramp slope of 12:1 is desirable. If space limitations do not allow a 12:1 slope, then an 8:1 slope is acceptable.  In cases where space is limited and where pedestrian traffic is light, a ’maximum slope of 6:1 may be used. The length of the ramp slope will be termed the “Y” distance.

Side Slope - The side slope is primarily determined by the curb height.  The desirable side slope is about 12:1. However, the “X” dimension should not exceed 6 feet; therefore if the curb height is more than 6 inches, the “X” slope will exceed 12:1.  Furthermore, where there are space constraints the "X” distance may be reduced to 4 feet and sloped to exceed 12:1.  In areas where pedestrian traffic is very light a maximum “X” slope of 6:1 is permissible.

The length of the side slope, measured along the curb line, will be termed the “X" distance.  Some special considerations of the “X” are as follows:

1. When the ”X” slope is adjacent to a landscaped parkway or encompasses a single pole, utility pole, etc. as illustrated in Figure E 632.212, use an x = 4.
2. Where the top of the “X” slope is within 1’ of the B.C.R., use the B.C.R. as the top of “X” slope as illustrated in Figure E 632.211A.
3. The “X” portion of the ramp near the top serves as a transition from the ramp to the sidewalk* Therefore no landing at the top of the ramp is needed.

E 592.3 Width of Ramp

Use width of w = 4' dimensioned on the curb.  Where the ramp narrows away from the curb, maintain a minimum of 3' at the top of the ramp.

E 592.4 Curb Face

Use ½-inch curb face, with a specified tolerance of zero inch plus and 1/8-inch minus in the “W” portion of the ramp as shown in the sketch below.

Though no curb is desirable for people who use wheelchairs, it is a distinct safety feature for people with low or no vision.  With no curb in the ramp, a person with low or no vision could leave the sidewalk and enter the street without knowing it.  Therefore, a small curb face is necessary to help people with low or no vision locate the curb line.

E 592.5 Texture

The texture on the ramp surface shall be rougher than the texture used on the surrounding sidewalk. The rough texture will provide the necessary non-slip surface on the steepened grade.  The change in texture will also help to warn a blind person of the ramp's presence.

1. In all cases, a ramp shall have a wood float or rougher finish.
2. In sidewalks constructed with terrazzo, pavers (brick, tile, or granite block) or any other special surface, the ramps shall be constructed of a material with rougher texture.

E  592.6 Miscellaneous Design Considerations

The designer will encounter special situations which should be given special considerations such as the following:

1. Where drainage conditions will permit, it may be desirable to raise the flow line ’of the curb return to provide a reduced curb face to accommodate ramps.  The reduced curb height will help to shorten ramps placed in narrow sidewalks and/or reduce the slope of the ramps.
2. Where there is a narrow sidewalk and the flow line of the gutter cannot be raised to reduce the curb height, it may be possible to drop the elevation of the back of the sidewalk to accommodate a ramp.
3. At intersections where pedestrian crossings of one street are restricted, or not desirable, the ramps should be oriented to the direction of pedestrian flow as illustrated in Figure E 632.212 (Type C).
4. Ramps should not be provided along streets where grades are so steep that they cannot be safely used by people with disabilities.

E 592.7 Coordination

Department of Transportation

It is necessary that the access ramps be located within the limits of marked crosswalks.  In some cases, it may be desirable to adjust the location of crosswalk lines to make them compatible with the best location for the ramps.

The Geometric Design Section of the Department of Transportation (DOT) should be consulted for assurance that adjustment of the crosswalk location will be accomplished when necessary for compatibility with a proposed ramp.

The Geometric Design Section of the DOT should also be consulted when particular problems are encountered at the following types of street intersections:

1. "T" Intersections
2. Jogged
3. Sharp angle
4. Multi-leg

Bureau of Street Services 

The construction of curb ramps, if confined to the limits of a specific project, would in many cases result in a ramp at only one corner of an intersection.  Under this condition, a person with disabilities could be trapped in an intersection which had no exit other than the entrance way.

Types of projects on which this might occur include permit work and assessment projects.  Permit work in connection with private development generally does not extend beyond the street center lines or beyond the centers of intersections at the ends of the project.  Assessment projects are also normally terminated at the centerlines of street intersections for convenience in setting assessment district boundaries.

To assure that adequate access ramps will be provided at intersections where construction work is to be undertaken the design offices should take the following actions:

1. On publicly financed projects (CIP, Combination), complete ramping shall be provided at all intersections involved.
2. On other projects (B-Permit, Assessment), if a ramp is installed at one corn, ramps at other corners shall be installed by the Bureau of Street Services upon request.  The Street Maintenance work should be coordinated with the Permit or Assessment permit construction.
3. Memorandum requests to the Bureau of Street Services for ramp construction shall be considered routine correspondence in accordance with Subsections B123 and B131 of the Office Guide. Copies of such memoranda shall be directed to the Engineer of Design who shall maintain a Citywide record of such requests.
4. Plans prepared for Street Services projects shall include ramps required in the intersection involved.