Manhole covers, grates, and obstructions should not be located within the curb ramp, maneuvering area, landings or turning spaces. Where they must be located in the ramp or landing, they must be firm, stable, and slip resistant. Curb ramps should not be located where pedestrians must cross drainage structures such as inlets and manholes. Where a drainage grate must be located in the path of pedestrian travel, it must be ADA compliant with openings that prohibit passage of a sphere larger than ½ inch. In new construction, curb ramp design must consider both the location of the curb ramp and the drainage and utility structures. Additional drainage inlets should be located on the upstream side of all curb ramps where practical in order to avoid running water across the bottom of the ramp. Curb ramps must be located away from low points of the curb return. For more information on drainage design, see .

The basic components to the standard curb ramp design are the following and are shown in (see for specifications on each element):

The grade of a curb ramp (also referred to as the running slope) is the grade measured along the direction of pedestrian travel. The grade of the curb ramp should be a maximum of 8.3 percent (1V:12H)

Transitions from the curb ramp to gutter and/or road surfaces must be flush (level) and free of abrupt surface changes. Gutters and/or road surfaces immediately adjacent to curb ramps must have a maximum counter-slope of 5 percent toward the curb ramp. However, a rapid change in grade at the base of the curb ramp and gutter may be difficult for wheelchair users if the footrests or anti-tip wheel cannot clear the ground surface. Therefore, the maximum recommended change in grade between a curb ramp and gutter (or road surface) is limited to 13.3 percent. If the algebraic difference in grade exceeds 13.3 percent, a 24-in level strip (maximum 2 percent slope) must be provided to transition from the curb ramp to the gutter (or road surface) to avoid tripping concerns (see )

The curb ramp cross slope is the slope perpendicular to (i.e., across) the direction of pedestrian travel on the curb ramp. The cross slope of the curb ramp should not exceed 2.0 percent at stop and yield controlled intersections, and 5 percent at signalized and uncontrolled intersections. At midblock pedestrian street crossings, will permit curb ramp cross slopes to be equal to or less than the street or highway grade. It is desirable to closely match the street grade because introducing warping of the cross slopes on the ramp can cause people with mobility disabilities to lose contact with one of their wheels on the ramp and cause instability.

It is recommended that the curb ramp be the full width of the sidewalk or approaching shared use path. The minimum width of a curb ramp or blended transition connecting to a sidewalk is 4-ft, exclusive of flared sides. The minimum width of a curb ramp or blended transition connecting to a shared use path is at least as wide as the shared use path. Refer to the latest for ramp types.

A turning space is a landing area that allows users to maneuver and make turns to travel on and off the curb ramp. Turning spaces may overlap the path of travel for pedestrians who are continuing along the sidewalk and do not want to cross the street. The maximum slope for a turning space is 2.0 percent in the direction perpendicular to the curbline and less than or equal to the grade of the roadway perpendicular to the curb ramp. Where a turning space serves two curb ramps, the slopes must be less than or equal to the parallel roadway grades. The minimum dimensions of a turning space are 5-ft x 5-ft. They should be provided at either the top or bottom of the curb ramp depending on curb ramp type or design, and/or whenever a turning maneuver is needed for pedestrians to maintain their orientation to the direction of the ramp.

At the bottom of curb ramps, the space within the street (at the gutter) serves as a clear area to traverse to and from the curb ramp. The minimum dimensions for this clear area are 4-ft x 4-ft, and the clear area must be located wholly outside of travel lanes (including bicycle lanes) that run parallel to the crosswalk. The slopes of the clear area are governed by the crosswalk cross slopes as discussed in 19.4.4.2.

Curb ramps must contain a detectable warning surface that consists of raised truncated domes that comply with . Detectable warning surfaces must be used at the following locations on the pedestrian access route:

Boarding platforms for rail vehicles where the edges of the boarding platform are not protected by screens or guards;

Detectable warnings must contrast visually with the adjacent surfaces, either dark on light or light on dark. Detectable warning surfaces must extend a minimum of 2 ft in the direction of pedestrian travel and must extend the full width of the curb ramp or blended transition; however, where a concrete border is required for proper installation of a detectable warning surface, a concrete border not exceeding 2 inches shall be permitted on all sides of the detectable warning surface except between the detectable warning surface and the edge of pavement where a setback is already permitted. Detectable warning surfaces are generally placed at the back of the curb or edge of street and they may be curved along the corner radius. For directional curb ramps the detectable warning surfaces must be placed at the bottom of the grade break except where one edge of the detectable warning surface would be greater than 5-ft from the back of curb.

Detectable warning materials must meet current materials specifications.

Side treatments of curb ramps include flares and returned curbs. See images below for an example of flares and returned curbs. depicts the different types of side treatments.

Flares must be provided for curb ramp designs where the pedestrian circulation path crosses the curb ramp. Flares are not intended to be part of the pedestrian access route. Flared sides must be sloped no more than 10 percent measured parallel to the curb.

Returned curbs do not use flares, but instead use curbs on the sides of the curb ramp. Returned curbs may only be used where a pedestrian circulation path does not exist along the edge of ramp, either because the adjacent surface is planted, substantially obstructed, or otherwise not meant for pedestrian travel.

Curb ramps are classified as perpendicular, directional, parallel, combination or blended transition per .

Diagonal curb ramps, defined as one ramp serving two crossing directions, are no longer permissible and may only be used where existing physical constraints make it technically infeasible to construct two curb ramps or a blended transition. Such ramps are typically not aligned with either of the crosswalks that extend across the intersecting streets. These ramps may direct a pedestrian with vision disabilities directly toward the center of the intersection.

Perpendicular curb ramps are designed to be perpendicular to the curbline and are the preferred ramps for application over parallel and directional curb ramps. depicts a perpendicular curb ramp.

Where practical, the curb ramp path should be aligned with the crosswalk; however, at large curb return radii, it may not be possible to provide a curb ramp that is both aligned with the crosswalk and exactly perpendicular to the curb face, and in these cases a directional curb ramp should be considered (see ).

Parallel curb ramps have two ramps leading down towards a center level landing at the bottom between both ramps. Since pedestrians must make a turning movement at the bottom of the ramp to align themselves with the street, it is crucial to provide a turning space at the base of the ramp. Parallel ramps are one solution on narrow sidewalks where perpendicular ramps are not feasible. Parallel curb ramps typically include a curb wall at the back of the ramp. shows an example of a parallel curb ramp.

Directional curb ramps are designed to align with the pedestrian crosswalk direction. Where a perpendicular ramp alignment would exceed a 20-degree angle with the direction of the crosswalk, a directional curb ramp should be considered. Directional curb ramps are designed like perpendicular ramps; however, instead of aligning perpendicular to the curbline they align parallel with the crosswalk. Directional curb ramps require the curb ramp grade breaks to be perpendicular to the direction of pedestrian travel, and result in a triangular clear area at the bottom of the grade break which must not exceed 2.0% in the direction of pedestrian travel.

Other types of curb ramps include combination curb ramps, blended transitions, and ramps at median islands. They are facilities that combine design elements of both perpendicular and parallel curb ramps. Slopes, widths, and other conditions must be consistent with common curb ramp requirements. Combination curb ramps are useful in areas with physical constraints and areas with high sidewalks. Note, the secondary ramp is considered part of the combination curb ramp and may not meet sidewalk ramp requirements. depicts the components of a combination curb ramp.

With a blended transition, the sidewalk elevation is lowered to the street level with a gradual change in slope. The maximum grade in the direction of pedestrian travel is 5 percent, provided there is a pedestrian access route at the top of the slope to allow people traveling on the sidewalk to bypass the blended transition. Otherwise, the maximum slope is 2.0 percent. Blended transitions without accessible pedestrian signals (APS) should be used sparingly since they do not provide directionality for pedestrians with vision disabilities. shows an example of a blended transition curb ramp.

Pedestrian refuge islands typically provide a level cut-through at medians, splitter islands, and channelizing islands. The minimum clear width of the pedestrian refuge is 5-ft or as wide as the shared use path if connecting to a path. The width of the median must be at least 6-ft or greater to serve as a pedestrian refuge. Tactile detectable warnings must be placed no more than 6-inches from the edge of the travel lane (or at the back of curb) and the two detectable warning panels must be separated by at least 2-ft; as such, if the median width is only 6-ft wide the detectable warning surfaces must be placed at the face of curb to provide the 2-ft of separation. For medians less than 6-ft, a pedestrian refuge is not provided and detectable warnings shall not be utilized. shows a level cut through with median refuge. provides an option if a wider median area is available.

Curb ramps that meet ADA standards do not need replacement. However, curb ramps that do not meet ADA standards, must undergo evaluation to determine whether and how they will need to be replaced or retrofitted.

Criteria for installing or updating curb ramps include:

Maintenance projects do not trigger an evaluation of existing curb ramps and the addition of new curb ramps. Examples of maintenance activities include, but are not limited to the following treatments or their equivalents:

Where existing physical constraints make it technically infeasible for altered elements, spaces, or facilities to fully comply with the requirements of , compliance with the ADA is required to the maximum extent feasible within the scope of the project. A variance application must be submitted for any element that does not achieve full compliance.