Chapter 4 - Design Solutions

by Daniel L. Dawson, PE, Otak, Inc & ITE; Elizabeth Hilton, PE, Texas Department of Transportation; Lee R. Kenderdine, PE, and Chuck Yancey, Metropolitan Government of Nashville and Davidson County, Tennessee

Until recently, there have been few design tools available to transportation practitioners for creating accessible pedestrian facilities. For the most part, pedestrian systems have been designed for a user who is agile and who sees, hears, and understands the roadway environment. But just as vehicular ways are engineered for users who have particular requirements—transit, large trucks, and emergency vehicles—so, too do sidewalks need to be planned for a broad range of pedestrians. Implementing accessible design results in a safer and more usable system for all, not just those with disabilities, in part because it requires that a greater level of detail and attention be given to pedestrian issues and improvements.

In the past, design of accessible pedestrian features has been inconsistent because authoritative design guidance has been lacking. And adjusting the geometrics in an existing system—the subject of this technical assistance—takes a much greater degree of creativity, thought, and engineering know-how than starting from scratch on a new project.


	PROWAAC members observe a thin-film detectable warning retrofit on an existing curb ramp in a pilot project in Portland, OR.

Resources

This section includes hypothetical situations and potential design_solutions that will vary depending on roadway conditions. The discussions and solutions in this chapter are based on practical applications, research, recommendations, and existing design standards from:

Building a True Community (January 2001), Public Rights-of-Way Access Advisory Committee's report to the US Access Board;
Designing Sidewalks and Trails for Access, Part II (August 2001), Federal Highway Administration;
Notice of Availability of Draft Public Rights-of-Way Accessibility Guidelines (June 2005), US Access Board;
Manual on Uniform Traffic Control Devices and draft changes approved for 2008;
Guidelines for Accessible Pedestrian Signals, NCHRP 3-62, University of North Carolina Highway Safety Research Center;
Guide for the Planning, Design, and Operation of Pedestrian Facilities (July 2004), American Association of State Highway and Transportation Officials; and
Chapter 6 of this special report

Accessible Design is a Safety Best Practice

Pedestrian interactions with motor vehicles bring safety risks. For instance, the lack of pedestrian signage and signal information in usable formats puts people with visual disabilities at a greater risk than those who can see. The 30-year-old cuckoo-chirp technology for providing crossing information to people with visual disabilities has been replaced by modern electronics that tick, talk, vibrate, audibly advertise their presence, adjust to ambient sound, and provide a wide range of other information (mapping, street names, special messaging, audio beaconing). Over 30 manufacturers now provide stand-alone or pedbutton integrated APS devices, including some that are receiver based for individual use.

The MUTCD includes standards and guidance for the placement and application of APS in Chapter 4. APS technology can significantly improve the access and safety of pedestrians with impaired vision because the crossing information is provided in multiple formats. As with other accessible design criteria, the usability of APS technology will depend on attention to detail and consistent inclusion of APS when designing and constructing signal systems. Where push buttons are placed at crosswalks and curb ramps, two buttons at each corner (one at each curb ramp) are critical for people with disabilities to understand which street crossing has the ‘walk' phase and to position themselves at the crossing before the walk phase starts.

The boundary between the sidewalk and roadway is not easy to detect if a person cannot see it, and stepping into the street without knowing it can be a significant safety problem. People with visual disabilities relied on curbs for that information before the advent of curb ramps. Detectable warnings (DWs), a pattern of low truncated domes, placed where the curb has been eliminated to provide wheelchair access, provide underfoot information on where the sidewalk ends and the street begins.


	Curb ramp with returned curb adjacent to landscape strip

The safety of wheelchair users is compromised when all four wheels do not maintain contact with the ground. This happens when sidewalk surfaces and transitions to the curb ramp and crosswalk are warped or there is a change in level—very common occurrences in the pedestrian environment. Steep grades and cross slopes can create similar stability, control, and tipping and falling problems for ambulatory pedestrians who use mobility devices. Many of these situations could be eliminated with greater attention paid to detailing pedestrian facilities during the design phase.

All these issues are accessibility and safety issues; the two are difficult to separate from one another in the pedestrian environment.

Information in This Chapter

The Case Studies used as examples in this report represent different, and not always optimal, approaches to streetscape alterations under a range of existing conditions. Some solutions are more successful than others and PROWAAC Subcommittee members did not agree on every photograph included here. Their use in this document should not be interpreted to indicate that they represent satisfactory or complete solutions. Each situation needs to be evaluated on a case-by-case basis using applicable standards, or, where standards are absent or inapplicable, best practices developed in concert with users and other experts.

Please note that in most design_solutions, crosswalk markings are shown. To avoid giving the user the impression that a certain type of crosswalk marking is preferred, different types of markings are shown. These illustrated crosswalk markings are applied at random in the illustrations and aren't intended to convey that one is preferable over another for the specific design_solution.

We have tried to use common industry terms, but you may find regionalisms in the text (we have used ‘bulb-out' instead of ‘curb extension', for instance). Your agency or firm may also characterize alterations differently. Our use of ‘alterations' is derived from the civil rights legislation and does not conform with the common industry practice of viewing ‘re-surfacing' as a maintenance item.

It isn't always possible to find photo illustrations that comply fully with accessibility criteria. So you will see in these pages curb ramps without detectable warnings and pedestrian signals and push buttons that provide only visual information. We've tried to note these discrepancies in the text and captions.

Design approaches illustrated here are familiar ones that exist in every pedestrian engineering toolbox.

Legend for Chapter 4 Design Solutions
APS*		Curb
DWS		Right-of-Way

* Face of pushbutton device should be aligned with crosswalk direction.

Reducing Curb Radius

In many solutions offered here, the curb return radius has been reduced to aid in solving the design issues. If curb or roadway reconstruction can be included in a project's scope, it may be possible to reduce the curb radius and so improve pedestrian access and safety. Reduced curb radii generally provide a larger area for pedestrian space (including curb ramps) at an intersection and are encouraged where turning movements and street widths allow. This is generally a benefit for all pedestrians and may even reduce delay for vehicles if crossing distances are less. However, designers will need to consider ways of satisfying turning radius requirements for larger vehicles.

Installing Accessible Pedestrian Signals

Wayfinding for pedestrians with visual impairments is significantly improved with the incorporation of APS at signalized intersections; APS are the most commonly-requested accommodation under FHWA's 504 regulation. Draft PROWAG specifies APS that are integrated with the pedestrian push button and include a tactile arrow and audible and vibrotactile indications. Audible signals mounted on the pedestrian signal head (as has been typical in the U.S.) would not meet the PROWAG provisions for placement or for vibrotactile indications. These new types of devices are intended to be installed close to the departure location and are typically only audible 6 to 12 feet from the push button, unless special beaconing features are installed. Push button locator tones are also a required feature and volumes of the walk indication and push button locator tone automatically adjust in response to ambient sound (+2-5dB).


	APS may need to be installed on a new stub pole at the departure curb for optimum usability.

The drawings in this chapter and in Chapter 6 show ideal placement of the push button-integrated APS in each illustrated solution. Placing the APS close to the landing and on the side away from the center of the intersection is best. The process of determining APS placement should include a careful study of:

directionality (aligning the tactile arrow with the direction of travel on the crosswalk);
avoiding ambiguity caused by placing two APS close together, where which button is sounding cannot be distinguished;
limiting the need for significant reorientation from the push button to the curb; and
reach and surface conditions for a pedestrian using a wheelchair.

The MUTCD 2003 specifies that two APS devices on a corner should be separated by at least ten feet. The separation often can be provided by installation of a stub pole for at least one of the APS devices, with the other located on the signal pole. In alterations situations, constraints may prevent this separation of devices. If two APS on a corner must be placed closer than ten feet, speech walk messages and additional custom features providing specific information about the crossing are recommended. Additional information can be found in the final report of the National Cooperative Highway Research Program Project 3-62, Guidelines for Accessible Pedestrian Signals.

When installing APS, the designer should select a unit with a push button locator tone, audible and vibrotactile WALK indications, tactile arrow, and automatic volume adjustment. Other features, such as audible beaconing upon request should also be analyzed and considered during the design phase. In all cases, the face of the device and the tactile arrow should be aligned with the direction of travel on the crosswalk, not aimed at the crosswalk or aligned with the ramp orientation. This becomes increasingly important if the location of the button is compromised by some existing physical constraint that prevents the use of an ‘ideal' location in an alteration.


	This wide Main Street in a historic town has been improved with the addition of medians and parking-lane landscaping at a midblock crossing. The curbed planters have been cut through at the crossing and along the curb to maintain drainage; the edges provide good non-visual wayfinding cues. Still needed: detectable warnings at the street edge, where there is no indication of the change from pedestrian to vehicular way.

Photo shows a pedestrian crossing of a wide Main street in a historic western town.

This wide Main Street in a historic town has been improved with the addition of medians and parking-lane landscaping at a midblock crossing. The curbed planters have been cut through at the crossing and along the curb to maintain drainage; the edges provide good non-visual wayfinding cues. Still needed: detectable warnings at the street edge, where there is no indication of the change from pedestrian to vehicular way.

Bulb-outs/Curb Extensions

In several design_solutions, the use of bulb-outs is proposed. Extending the curb at a crossing works well at locations with on-street parking. Other design_solutions suggest tapering the street width to allow additional space at the curb returns. In each of these applications, the curb has been moved closer to the centerline of the street. This will likely result in a change in the drainage flow along the street surface. Sidewalk cross slope may be improved, since it is likely that the roadway surface being used is more level. Some curb height may be sacrificed.

Combination Curb Ramps

The use of combination curb ramps (combining a parallel ramp in the sidewalk, a level landing for a turn, and a short perpendicular run to the street) can make the most of limited sidewalk width.

Reduced Curb Height and Installation of Bollards

Reducing curb face exposure to limit the need for a longer curb ramp can lead to vehicles riding up on the curb corners as in flush curb applications. Some jurisdictions may use bollards to avoid such incursions. If they are provided, it is critical that the bollards have high visual contrast with the background.


	Sometimes difficult topography requires extraordinary solutions. In this photograph of an older Ohio residential neighborhood, the existing roadways are much lower than the sidewalks and separated by wide sloping lawns. New stairs and ramps—both with handrails—make the connection to the street crossing for pedestrians.

	A perpendicular curb ramp with side flares and a top landing is shown. The ramp run does not end at the curb, but extends across the gutter to meet the street at a higher elevation, making it possible to accommodate a perpendicular ramp and landing in a narrow sidewalk and eliminating the effects of the gutter counterslope. Short reverse flares extend back to the curb face.

Extending the Curb Ramp Across the Gutter Pan

Some of the design_solutions include extending the curb ramp across the gutter pan where insufficient space exists to provide both a curb ramp and a landing. In most cases, the height of the curb ramp across the gutter pan will be minimal (two inches or less) but the side slopes of this extension should be tapered out at a minimum slope of three horizontal to one vertical. Generally, placing an obstruction in the flow line of the gutter is undesirable, but it is a small sacrifice for providing a suitable curb ramp and does avoid ponding at the toe, which can hide a problematic lip or freeze in cold weather. Consider the drainage impacts of the installation and consider adding a catch basin just upstream of the obstructed gutter pan. Another solution is a narrow (one inch) cast iron trench drain across the ramp toe to collect drainage.

Design Problems

The design_solutions for the hypothetical problems described in the following pages have been developed in conformance with recommendations of the PROWAAC (Building a True Community) and the draft PROWAG published by the Access Board in November 2005. During the PROWAAC meetings, relevant MUTCD 2003 provisions were harmonized with PROWAG technical specifications, a process that continues with the preparation of the 2008 MUTCD. The Subcommittee also coordinated its work with development of the AASHTO pedestrian guide.

The problem statements are organized as five different types, based largely upon the nature of the principal constraint:

Limited right-of-way
Above-ground obstructions
Push buttons are not accessible
Excessive roadway slope
Underground obstructions

Constraint—Limited Right-of-Way

Acquire Additional Right-of-Way

Problem Statement

Not enough room for curb ramp and landing

Problem and Design Solution Discussion

Design Solution 1.01

Application Considerations

Acquire sidewalk easements.
Acquire right-of-way dedication.
Purchase additional right-of-way.
Expanded sidewalk area will provide a larger area for pedestrians to gather/wait, and more room for curb ramps, landing, signal equipment, etc.
May require alterations to building and/or other structural features located at or near corner.
Sometimes acquisition of right-of-way is a long and costly process or not feasible.

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Elevate Intersection to Sidewalk Level

Problem Statement

Not enough room for landing and curb ramp slope will be too steep.

Problem and Design Solution Discussion

Existing street improvements, including vehicle lanes and sidewalks, consume the entire right-of-way. Often there is insufficient space for the installation of an accessible curb ramp and landing at a street intersection that will meet new construction standards. Another potential solution is to raise the entire street grade at the intersection to make the sidewalk elevation flush with the street elevation, thus eliminating the spatial needs for curb ramps. It is critical in this application to provide detectable warning surfaces to provide a detectable alert to blind and visually impaired travelers, which indicate that they are entering a street. Raising the entire intesection can be a wayfinding issue for the blind; raised crosswalks alone are better as blind pedestrians can recognize the curb between the raised crosswalks.

Design Solution 1.02

Application Considerations

Potentially increases construction costs.
May require street drainage changes/additions.
Continuous detectable warning surfaces are required to delineate pedestrian area from the street area.
May require the installation of APS signal equipment.
Consider raised crosswalks as an alternative.
If provided, bollards should have high visual contrast to background (dark/light or light/dark).

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Extend Curb Ramp Over Gutter Pan

Problem Statement

Not enough room for landing and curb ramp.

Problem and Design Solution Discussion

Design Solution 1.03

Application Considerations

The extension of the curb ramp through the gutter may have an impact on drainage.
Detectable warnings must be placed at the back of curb line even though the curb ramp extends beyond this point to alert pedestrians with limited vision that they are stepping into the street.
May require the installation of APS signal equipment.
Avoid extending projecting curb ramp into travel lane.
May encourage pedestrians to wait in the street portion of curb ramp.
Stop bar may increase driver awareness of curb ramp.
Consider using in conjunction with on-street parking to allow room for projecting curb ramp.

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Use Combination Curb Ramp

Problem Statement

Not enough room for landing and curb ramp.

Problem and Design Solution Discussion

Design Solution 1.04

Application Considerations

The face of the building must accommodate the additional exposure of lowering the sidewalk four inches in front. Detectable warning placement is important to alert pedestrians with visual impairment that they are about to cross the street.
Providing some perpendicular ramping eliminates the potential for ponding at the landing.
If provided, bollards should have high visual contrast to background (dark/light or light/dark).
Placement of APS close to buildings and other hard vertical surfaces creates directional sound interpretation issues for blind pedestrians and should be avoided.

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Lower Sidewalk to Street Surface (Blended Transition)

Problem Statement

Not enough room for landing and curb ramp.

Problem and Design Solution Discussion

Design Solution 1.05

Application Considerations

Potentially increases construction costs.
May require street drainage changes/additions.
Continuous detectable warnings are required to delineate pedestrian area from the street area.
Placement of APS close to buildings and other hard vertical surfaces creates directional sound interpretation issues for blind pedestrians and should be avoided.
If provided, bollards should have high visual contrast to background (dark/light or light/dark).

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Parallel Curb Ramp

Problem Statement

Not enough room for landing and curb ramp.

Problem and Design Solution Discussion

Existing street improvements, including vehicle lanes and sidewalks, consume the entire right-of-way. Often there is insufficient space for the installation of a perpendicular curb ramp and landing at a street intersection that will meet new construction standards. A potential solution would be to design a parallel curb ramp instead of a perpendicular curb ramp.

Design Solution 1.06

Application Considerations

All users of the sidewalk will have to traverse the curb ramp. If bypassing the crossing, the user would have to descend to the landing and ascend back to the sidewalk level.
Possible variations on the parallel curb ramp that could be used if sufficient space is available are a split sidewalk or a combination curb ramp.
If existing drainage is poor, debris and silt can accumulate in the landing.

Related Design Standards

Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Reduce Street Width and Provide Combination Curb Ramp

Problem Statement

Not enough room for landing and curb ramp.

Problem and Design Solution Discussion

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners. The building location has limited the location of curb ramps and landings. Existing street improvements consume the entire right-of-way. In this example, street width has been reduced to provide adequate space to use a combination sidewalk ramp and curb ramp to achieve the required 1:12 slope from curb height to street grade.

Design Solution 1.07

Application Considerations

May require street drainage changes/additions.
Significantly increases construction costs.
Expanded sidewalk area will provide a larger area for pedestrians to gather/wait, and more room for curb ramps, landing, and signal equipment.
Providing curb extensions reduces roadway width, which works well if the street has on-street parking. If not, then this solution may not be possible.
This application assumes that the sidewalk can slope adjacent to the building.
Reduces crossing distance for pedestrians.
Curb extensions normally provide effective traffic calming.
The transition from the existing sidewalk to the curb ramp landing elevation is not required to exceed 15 feet in length.
Placement of APS close to buildings and other hard vertical surfaces creates directional sound interpretation issues for blind pedestrians and should be avoided.

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Reduce Street Width and Provide Combination Curb Ramp

Problem Statement

Not enough room for landing and curb ramp.

Problem and Design Solution Discussion

Existing street improvements consume the entire right-of-way. In this example, the building is built out to the right-of-way and there is inadequate space to provide curb ramps. This solution uses a reduced curb radius and combination curb ramp to accommodate the shortened perpendicular portion of the curb ramp.

Design Solution 1.08

Application Considerations

Expanded sidewalk area will provide a larger area for pedestrians to gather/wait, and more room for curb ramps, landing, signal equipment.
May require alterations to building doorways located at or near corner.
Increases motorist's visibility of pedestrians at the corner.
May require street drainage changes/additions and increased construction costs.
May not accommodate all right turning vehicles. Check vehicle types for turning radius requirements. If receiving street is multi-lane, a smaller right turn radius is less problematic.
Placement of APS close to buildings and other hard vertical surfaces creates directional sound interpretation issues for blind pedestrians and should be avoided.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Limited Right-of-Way

Parallel Curb Ramps Provide Access to Parking Space

Problem Statement

Insufficient sidewalk space to accommodate a perpendicular curb ramp to serve the 13-foot wide on-street accessible parking space.

Problem and Design Solution Discussion

Accessible parking spaces with access aisles and accessible connections to the sidewalk must be provided at on-street parking locations where the existing sidewalk widths are 14 feet or greater. For sidewalks less than 14 feet in width, accessible parking spaces must be provided, but access aisles are not required. When access aisles are not provided to connect to the PAR, the accessible parking space must be located at the end of a block face to utilize the corner curb ramps. Where adequate sidewalk width exists, accessible sidewalk connections and the PAR can be created by either providing a curb extension out to the edge of the parking lane and reducing the sidewalk width to provide space for unloading and using the PAR. Another option is to simply reduce the sidewalk width by four feet and use this reduced width as the PAR and unloading area.

Design Solution 1.09

Application Considerations

May require some regrading of street to accommodate revised drainage flow patterns.
May require the addition of new storm drainage collection facilities.
Provides ability for wheelchair and scooter users to unload on the street pavement outside of traffic lanes and have ramped connections to the sidewalk.
Reduces the width of sidewalk available for general use.
Parking space should be set back from the crosswalk and/or stop sign (if one exists) to maintain safe visibility.

Related Design Standards

Local Municipal Parking Codes
Local Municipal Design Standards
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Relocate Obstruction

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Existing elements at a corner cannot be eliminated. In this example, the fire hydrant was moved to a location that eliminated its interference with the curb ramp installation. Because there is insufficient space for a full landing and conventional curb ramp, some ramping is provided in the sidewalk and some ramping is provided in the furnishing area.

Design Solution 2.01

Application Considerations

Increased cost to relocate existing fire hydrants, power poles, utilities, vaults, furniture, signage, etc.
Combination curb ramp avoids conflict with stairway and provides perpendicular section of curb ramp, with related drainage benefits.
Utility relocations can require extensive coordination.

Related Design Standards

MUTCD
AWWA
Local Municipal Specifications and Standards

Related Design Guidelines

PROWAG

Constraint—Above Ground Obstructions

Single Curb Ramp at Apex

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Obstructions in the intended paths of travel prevent the construction of a curb ramp for each direction of travel. However, the area at the apex of the corner is clear of existing obstructions. A single perpendicular curb ramp that serves both crossings may be the only alternative. Keep in mind, however, that two curb ramps, if possible, are always preferable to a single curb ramp at the apex.

Design Solution 2.02

Application Considerations

Single curb ramps serving two crossings are the least preferred.
Will not provide directional cue to pedestrians with visual impairments.
May not accommodate all right turning vehicles. Check vehicle types for turning radius requirements. If receiving street is multi-lane, a smaller right turn radius is less problematic.
Push buttons have been located as far apart as possible while maintaining close proximity to the crosswalk and the curb ramp landing. Separation of push buttons is desirable to clearly indicate which crossing is served by each button.

Related Design Standards

Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Install Combination Curb Ramp

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Placement of signal controller cabinets in the past failed to take into consideration the needs of pedestrians. Signal controller cabinets have been located for reasons of economy and convenience. Many of these units now block, or to a lesser degree, project into the PAR. If the base of the cabinet is sufficiently deep, it may be possible to use a combination sidewalk and curb ramp to achieve the appropriate layout. By ramping the sidewalk down three inches in the vicinity of the cabinet, it will be possible to reduce the length of curb ramp about three feet, thus providing adequate space for a landing.

Design Solution 2.03

Application Considerations

Will require a suitable cabinet base to work around.
Does not require acquisition of additional right-of-way.
Does not require rewiring of the controller.
Since APS post at back of landing would be too close to controller, move to front of landing at back of flare.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Relocate Signal Control Cabinet

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Design Solution 2.04

Application Considerations

May require rewiring of the signal to the cabinet.
Results in a typical curb ramp and landing installation.
May require purchase of additional right-of-way.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Relocate Signal Control Cabinet

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Placement of signal controller cabinets in the past failed to take into consideration the needs of pedestrians. Signal controller cabinets have been located for reasons of economy and convenience. Many of these units now block, or to a lesser degree, project into the PAR. When a cabinet blocks passage along a sidewalk or at an intersection, several options exist to achieve adequate clearance. Sidewalk can be extended to wrap around the back of the cabinet, or the cabinet may be rotated to provide clearance. If the cabinet is a pole-mounted cabinet, it could be relocated to a pedestal-mounted cabinet (built over a base, not mounted on the pole), or it could be rotated to be on the side of the pole that provides maximum passage clearance to the sidewalk.

Design Solution 2.05

Application Considerations

If a cabinet is pole mounted more than 27 inches above the ground and projects into the traveled way, a detectable curb or other cane detectable feature must be located beneath the cabinet for detectability.
Rotation of cabinets may require rewiring of the signal system.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Use Parallel Curb Ramps

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Design Solution 2.06

Application Considerations

Since the sidewalk will be lower adjacent to the cabinet, the cabinet base may require modification.
Earth cover over existing conduits running to the cabinet may be less than desirable.
Detectable warnings required to delineate pedestrian area from the street area.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Add Curb Extensions/Bulb-outs

Problem Statement

Existing appurtenances limit travel space and installation of accessible landings and curb ramps at corners.

Problem and Design Solution Discussion

Design Solution 2.07

Application Considerations

May require street drainage changes/additions.
Significantly increases construction costs.
Expanded sidewalk area will provide a larger area for pedestrians to gather/wait, and more room for curb ramps, landing, and signal equipment.
Providing curb extensions reduces roadway width and this will work well if the street has on-street parking.
Pedestrians will be more visible to motorists.
Motorists will be more visible to pedestrians.
Curb extensions normally provide a traffic calming effect.
Reduces crossing distance for pedestrians.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Above Ground Obstructions

Provide Blended Transition

Problem Statement

Accessible curb ramps and landings constrained by features that can't be modified.

Problem and Design Solution Discussion

Existing historic features or significant trees limit travel space and the installation of accessible landings and curb ramps at corners. In this example, a historic building is located close to the curb face at the intersection. The solution here is to provide a transition ramp from each approach direction and provide a blended transition at the corner.

Design Solution 2.08

Application Considerations

Will decrease pedestrian travel capacity. (Pedestrian pairs and groups will need to travel in single file.)
Increases conflicts between pedestrians traveling in opposite directions.
Building face/foundation must be able to accommodate changing sidewalk grades.
A similar solution would be to raise the intersection to sidewalk level.
More difficulty for blind travelers to determine directionality.
For APS, provide audible message at this
location since inadequate separation between
push button locations makes it difficult for
blind people to determine which push button guides each crossing.
Pushbutton location either at curb or near face of building.

Related Design Standards

Uniform Building Code
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Push Buttons Are Not Accessible

Add Stub Poles

Problem Statement

Pedestrian actuated signal push buttons at inappropriate locations.

Problem and Design Solution Discussion

Pedestrian actuated push buttons are often located on a central signal pole away from the curb ramps and do not facilitate efficient use by all pedestrians, including those with disabilities. Often the travel distance from the button location to the street is excessive. Also, crossing orientation is difficult for a blind pedestrian since the locator tone and both buttons are at the same location. Installation of stub poles with APS equipment and push buttons closer to the crossing solve these problems.

Design Solution 3.01

Application Considerations

Locate stub poles adjacent to level landing areas of curb ramps so wheelchair users can access buttons at a location where the wheelchair will remain stationary.
Higher cost due to removal and replacement of sidewalk to install underground connections to stub pole.
For parallel curb ramps, locate the stub poles at the back of sidewalk (landing).

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Push Buttons Are Not Accessible

Add Curb Extensions/Bulb-outs

Problem Statement

Pedestrian actuated signal push buttons
not at optimal locations.

Problem and Design Solution Discussion

Pedestrian actuated push buttons are often located on a central signal pole away from the curb ramps and do not facilitate efficient use by all pedestrians, including those with disabilities. In addition, corners often become the location for multiple poles that block the installation of curb ramps. One solution is to add curb extensions at the intersection to provide sufficient space for curb ramps and stub poles for APS and push buttons.

Design Solution 3.02

Application Considerations

Locate stub poles adjacent to level landing areas of curb ramps so wheelchair users can access buttons.
Higher cost due to removal and replacement of sidewalk to install underground connections to stub pole, but also could be a cost savings compared to the cost of multiple pole relocations.
Potential street drainage impacts.
Reduces crossing distances and times for pedestrians.
Pedestrians will be more visible to motorists.
Curb extensions normally provide a traffic calming effect.
Works well if there is on-street parking.

Related Design Standards

MUTCD
Local Codes and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Excessive Roadway Slope

Add Curb Extensions/Bulb-outs

Problem Statement

Existing street running grade
does not support level landings.

Problem and Design Solution Discussion

Street running grades in excess of 5% create challenges in the design and construction of accessible features at intersections. In some situations, the use of bulb-outs can create larger and flatter pedestrian areas at corners, which can accommodate flat landings and acceptable slopes on curb ramps.

Design Solution 4.01

Application Considerations

Corner curb extensions, or bulb-outs will provide additional space and allow for construction of a level landing.
Expanded sidewalk area will provide a larger area for pedestrians to gather/wait, and more room for curb ramps, landing, and signal equipment.
May require alterations to building doorways located at or near corner. Improves motorist's view of pedestrians at the corner.
Increases construction costs.
May provide an option to alter vehicle turning geometry and increase pedestrian gathering area.
The turning radius in this example is effectively shortened and may not accommodate all right turning vehicles. Check vehicle types for turning radius requirements. If receiving street is multi-lane, a smaller right turn radius is less problematic.

Related Design Standards

MUTCD
AASHTO
PROWAAC
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Excessive Roadway Slope

Problem Statement

Existing street running grade does not support level landings and acceptable crossslopes on crosswalks.

Problem and Design Solution Discussion

Street running grades in excess of 5% create challenges in the design and construction of accessible features at intersections. Modifying the street profile for the stop controlled street to ‘table' the crosswalk providing a 2% or less cross slope in the crosswalk improves the crosswalk and allows for acceptable curb ramp at each end of the crosswalk. Note that the 2% cross slope only needs to be achieved within the 4-foot PAR, not across the entire crosswalk.

Design Solution 4.02

Application Considerations

Revise intersection grades to create raised crosswalk.
May create less desirable profile for vehicular traffic.
May require street drainage changes/additions.
Increases construction costs.
Added difficulty in application of future pavement overlays.
May introduce travel/grade change problems for bicycles.
For steeper grades, longer grade transitions including vertical curves may be required.
May have to rebuild subgrade.
May impact drainage.

Related Design Standards

MUTCD
Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Excessive Roadway Slope

Regrade Roadway Profile to Provide Acceptable Cross Slope Across Intersection

Problem Statement

Existing street grade does not support
acceptable crossslopes on crosswalks.

Problem and Design Solution Discussion

In this example the existing north-south leg of the intersection has a 5% grade. One solution is to table the entire intersection approaches to accommodate flattened crosswalk cross slopes for both the north and south approaches to the intersection. Ideally, the tabling would be accomplished by lowering the upper half of the intersection and raising the lower half of the intersection. The achieved grade through the intersection would be 2%.

Design Solution 4.03

Application Considerations

Most appropriate when street is being reconstructed.
Most appropriate for lower speed roadway.
Revise entire intersection to create a level or flat surface.
Alteration of all approaches may be necessary to vertically blend grades with the intersection.
May require street drainage changes/additions.
Will likely result in significant engineering and construction costs.
Construction of flat intersection surface will potentially affect underground utilities, surface facilities, building entrances, transit facilities, and landscape features.
More suitable with fewer lanes.

Related Design Standards

Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Excessive Roadway Slope

Mill Street Crown to Reduce Crosswalk Running Slope

Problem Statement

Existing street running grade
does not support accessible crossings.

Problem and Design Solution Discussion

Many existing streets have been resurfaced several times and the resurfacing has resulted in the crown slope of the street getting steeper and steeper. As a result, crossing streets with steep crowns can become physically challenging when overlays have steepened the crown to more than 5%. One solution to reduce the crown slope and the resulting effort of a pedestrian in a manual wheelchair, is to mill the pavement surface back to a 2% crown as part of the resurfacing process.

Design Solution 4.04

Application Considerations

Reduces the crossing time of a pedestrian in a manual wheelchair.
Improves entrance and exit characteristics for vehicles parked at the curb.
Milled asphalt concrete pavement can be recycled as base material or as part of the asphalt concrete mix.
Increases the cost of overlay projects due to increased cost of pavement milling.
Makes the transition from the gutter to the street crown smoother, reducing the angle point.
Transition back to existing crown over the appropriate length of roadway for vehicular operations.
New pavement surface must be flush with curb ramp.

Related Design Standards

Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO

Constraint—Excessive Roadway Slope

Provide Median Refuge Area

Problem Statement

Existing street running grade
does not support accessible crossings.

Problem and Design Solution Discussion

Many existing streets have been resurfaced several times and the resurfacing has resulted in the crown slope of the street getting steeper and steeper. As a result, crossing streets with steep crowns can become physically challenging when overlays have steepened the crown to more than 5%. If it is not feasible to re-crown the street, it may help to provide a median refuge area for pedestrians, particularly on wider streets, as the steeper cross slope causes manual wheelchair users and others with little stamina, to take more time to cross the street and expend more energy.

Design Solution 4.05

Application Considerations

At signalized intersections, may allow for reduced pedestrian clearance interval since pedestrians can stop in the median.
At signalized intersections, provide pedestrian push buttons at median refuge area.
More benefit accrues for wider street applications.
At uncontrolled or stop controlled intersections, provides more crossing opportunities and less waiting time for all pedestrians.
Detectable warning surfaces are required for each edge of the refuge area.

Related Design Standards

MUTCD
Local Municipal Design Standards

Related Design Guidelines

AASHTO
PROWAG

Constraint—Underground Obstructions

Modify Structure

Problem Statement

Existing structures limit curb ramp alignment and usability.

Problem and Design Solution Discussion

Existing underground obstructions limit the installation of accessible features at intersection corners. These obstructions frequently include drainage structures, basement below sidewalks, utility vaults, and other similar structures. Often, the upper portions of these structures can be modified to accept the installation of landings and curb ramps. In this example, the intersection corner has been modified to use parallel curb ramps and the interfering vault has been modified by trimming the top walls and resetting the lid at the appropriate grade.

Design Solution 5.01

Application Considerations

Consult with vault manufacturer to determine if trimming sidewalls will compromise structure integrity of vault.
Consult with utility to determine if facilities contained within the vault will interfere with the sidewall trimming.
It is preferable to avoid locating the vault lid within the PAR. This alternative of trimming the sidewalls should only be done if it is not feasible to move the vault.
Can be a difficult and expensive solution.
An option would be to lower the vault lid four inches, and take up the remaining two-inch elevation change in the perpendicular portion of the combination curb ramp.

Related Design Standards

Uniform Building Code
Local Codes and Standards
National Electrical Code

Related Design Guidelines

AASHTO
PROWAG

Constraint - Underground Obstructions

Relocate Existing Vault

Problem Statement

Existing structures limit curb ramp alignment
and usability.

Problem and Design Solution Discussion

Existing underground obstructions limit the installation of accessible features at intersection corners. These structures frequently include drainage obstructions, basement below sidewalks, utility vaults, and other similar structures. Occasionally these structures can be relocated so that space will be available to accept the installation and far enough to allow the construction of the parallel curb ramp slope to the landing.

Design Solution 5.02

Application Considerations

Can be a difficult and expensive solution.
Preference for vault to be moved out of the pedestrian travel route to behind sidewalk, into street, or another location that keeps it out of the path of travel.
Involvement with utility companies complicates and can slow down the implementation process.
Often relocation of utility structures is not feasible.

Related Design Standards

National Electrical Code
Local Municipal Specifications and Standards

Related Design Guidelines

PROWAG

Constraint - Underground Obstructions

Reduce Curb Radius

Problem Statement

Existing structures limit curb ramp alignment
and usability.

Problem and Design Solution Discussion

Existing underground obstructions limit the installation of accessible features at intersection corners. Often these obstructions cannot be modified or relocated. In this example, the large radius of the intersection combined with the location of a large underground vault has limited the ability to provide an acceptable curb ramp and landing in the south portion of the corner. The solution is to reduce the curb return radius from 20 feet to 10 feet, thus creating space for the standard curb ramp and landing, using a shared curb ramp.

Design Solution 5.03

Application Considerations

Decreasing the curb radius may provide additional space and allow for construction of a level landing and curb ramps.
Expanded sidewalk area will provide a larger area for pedestrians to gather/wait, and more room for curb ramps, landing, and signal equipment.
Increases motorist's visibility of pedestrians at the corner.
Verify that reduced radius can accommodate typical intersection traffic.
Potentially increases construction costs.
May require street drainage changes/additions.

Related Design Standards

Local Municipal Design Standards
National Electrical Code

Related Design Guidelines

AASHTO
PROWAG

Constraint -Underground Obstructions

Use Returned Curb Ramp

Problem Statement

Existing structures limit curb ramp alignment
and usability.

Problem and Design Solution Discussion

Existing underground obstructions limit the installation of accessible features at intersection corners. Often these obstructions cannot be modified or relocated. Flared wings of curb ramps consume a large amount of space. Where the flare would otherwise require significant modification to the location or modification to the cover of an underground facility, the use of returned curbs adjacent to the obstruction may create a curb ramp that is narrow enough to fit adjacent to existing structures. Additional railing or other physical barrier may be needed to isolate this type of curb ramp and prevent trip/fall accidents at the location of the returned curb.

Design Solution 5.04

Application Considerations

Considerably less expensive than removing or modifying an underground structure.
Depending on the size and number of existing underground structures, two individual curb ramps may not be possible.
May result in additional maintenance cost for guide rails or other barriers used to isolate the curb ramp.
Potentially increases construction costs.
Provides an appurtenance close to the driving edge of the travel lane, which may be struck by an errant vehicle.

Related Design Standards

Local Municipal Specifications and Standards

Related Design Guidelines

AASHTO
PROWAG

Accessible Parking Spaces General Discussion

Problem Statement

Variable distribution of accessible
on-street parking spaces.

Problem and Design Solution Discussion

Location and availability of parking is a critical aspect of travel. The lack of accessible parking is a barrier to arriving at a destination if a person with a disability cannot park and exit from the vehicle. Limiting accessible parking to a central location may not be effective for someone with a disability because of a lengthy distance between the parking space and desired destination. Providing ample spaces at a variety of locations allows for access to work, shopping, recreation, and other activities.

Design Considerations

Some locations such as central business districts and civic centers may have more of a demand for accessible spaces.
Evaluate the topography. Select locations with minimal grades and cross slopes for ease of getting in and out of vehicles and traversing the surrounding area. Van lifts need a flat area for operation.
Analyze the condition of the surrounding curb ramps, landings, and sidewalks. Repair pedestrian elements that could be barriers.
Analyze the surrounding area for elements such as street furniture, landscaping, parking meters, and utilities that may block a person from entering and exiting a vehicle.
Provide space for parking larger vehicles and vans with adequate access aisle space for lifts and transferring when exiting and entering the vehicle.

Case Study—No ‘Good' Location for Curb Ramp

An existing storm sewer inlet made optimal location of an opposite side curb ramp problematic. The new curb ramps adjoin the two new APS signal posts on this corner and are situated at the edge of the marked crosswalk farthest from the center of the intersection.
An ‘all-red' signal enables crossing pedestrians to use the other curb ramp on the corner. Right turn on red is prohibited; signals and markings are installed for diagonal crossing.
An APS is needed to provide the necessary cue to crossing phase, since there is no parallel traffic stream to provide that information. Also needed: detectable warnings.

Notice

Planning and Design for Alterations

PROWAAC Special Report

Chapter 4 - Design Solutions

Technical Assistance