Chapter 3—Design Process

by Andrew Davis, PE, City of Akron, OH; Jerry Markesino, PE, Otak, Inc.; Jim McDonnell, PE, AASHTO; Bob Sexton, PE, HR Gray (Columbus, OH); Bill Hecker, AIA (Birmingham, AL), Ken Stewart, Council on Citizens with Low Vision, International

The design process for making accessibility improvements in alteration projects is not any different from the design process for traditional street modification projects. Incorporating accessible pedestrian elements in the public right-of-way requires the same reference to standards, technical guidance, and product information that designers follow in every roadway design project. The design and placement of curb ramps into an existing developed streetscape is governed by many of the same considerations as roadway design: controlling horizontal and vertical geometries, surface conditions, and access to intersections, all at the scale of the pedestrian rather than the vehicle.

In an alteration, a balance needs to be struck between pedestrian and vehicle users vying for travel space (and time) within a limited right-of-way already constrained by existing development. A good understanding of the rationale behind accessibility standards will help the designer integrate usability for pedestrians who have disabilities into agency decision making.

Resource: FHWA's ‘Designing Sidewalks and Trails for Access, Part 2' at:

Photo of temporary pedestrian route in street, protected by barriers.

This urban arterial passes through a neighborhood that is undergoing rapid revitalization, with many projects under construction temporarily occupying existing sidewalk space. In this example, the contractor has provided a temporary pedestrian route in the curb lane of the roadway, separating it with Jersey barriers and installing a temporary concrete ramp to the street level walkway. Still needed: detectable warnings at the cross street.

Gathering Information

A planned alteration project may arise from a long-planned Capital Improvements Program or be a more immediate response to local conditions or community advocacy. When such construction is undertaken, the new work must incorporate accessibility features. Jurisdictions may have additional obligations for existing facilities under the Title II and 504 regulations (see Chapter 2, Alterations).

Therefore, before developing the scope of work for a planned new project, the design team should contact the jurisdiction or agency ADA/504 Coordinator to identify accessibility improvements that may be needed within or near proposed project boundaries, such as:

  • curb ramp transition plans and schedules;
  • requested individual accommodations, including APS, parking, curb ramps, and sidewalk repairs; and
  • bus stop/transit accessibility improvements.

Often, such improvements can be included in a pending project at a more modest cost than undertaking them independently. Evaluate existing conditions near the project site to determine if key accessibility features or needed maintenance could be provided more economically by slightly expanding the project scope of work. Some agencies have developed ‘spot improvement' programs that use resident requests as input to project scoping. Coordination with transit agencies, which have their own ADA obligations for new construction, alterations, and existing facilities and programs, will indicate whether bus stop locations and shelter space and access requirements would best be addressed within a planned project scope. By gathering this information during preliminary project planning, the engineer can avoid potentially costly oversights and under-designs.

Resources: FHWA's ‘Metropolitan Planning' at:
FTA's civil rights/accessibility page at:
Transition Plan, City of Nashville, TN at: (see Section VIII: Compliance Strategies for Public Right-of-Way)
State of Hawaii Title II Self Evaluation and Transition Plan at:
A newly-funded (2006) National Cooperative Highway Research Project developing guidance for highway agencies on preparing transition plans and meeting program access expectations at:

Planning the Scope of Work

Defining the scope of a planned alteration project establishes the physical and contractual parameters of the work. If right-of-way is to be acquired for a project, it is important to purchase enough to accomplish all project objectives; if an existing right-of-way is to be reapportioned, the scope of work will fix the balance between motor vehicle, cycling, and pedestrian uses. Under-scoping a project may leave or create barriers that will have to be corrected; an oversight that renders a significant part of a planned project inaccessible can entail costly remediation.

New technologies such as central on-street parking pay stations and pedbutton-integrated APS must be carefully placed for usability. Signaling and utility equipment locations and sizes must be anticipated and the accessibility effects of street furniture (benches, bike racks, bus shelters, signage and other appurtenances) must be assessed before right-of-way needs can b e finalized. Private uses of public space for ATM access, sidewalk dining, and newspaper vending all have space and geometric design implications for accessibility.

Street and sidewalk modifications may also affect access to abutting properties. This can raise complex issues of engineering, coordination, and policy, particularly with private sector entities that have obligations under Title III of the ADA to provide accessible approaches and entrances. For example, correcting excessive cross slope as part of a sidewalk improvement project should not result in new steps at entrances to adjacent businesses. A detailed site study that includes consideration of beyond-the-right-of-way implications will best serve public/private coordination efforts and suggest design approaches and solutions (see Chapter 4), which will be helpful in addressing existing constraints in alterations, particularly those of modest scope.

Photo of entrances to shops on a sloping street with level access at top and steps at bottom.

This streetscape improvement in a historic downtown works with the street slope to provide individual entrance platforms at existing businesses. Level landings on the upside connect back to the downside with steps. A clear passage of 1.5 m (5 feet) is maintained between the furniture zone at the curb and the stepped entrance platforms.

A comprehensive scope of work description will include the following:

  • WHAT the proposed project is intended to do, including pedestrian accessibility objectives;
  • WHERE the project limits and bounds will be and how new and existing facilities will meet; and
  • HOW the project will be funded, including sources, availability, and limitations arrayed against estimates of design and construction costs (note the overview of funding sources for accessibility improvements included in the Appendix).

From this, the planning team will identify possible constraints that may affect roadway, pedestrian, and accessibility objectives. Several design schemes may have to be developed and analyzed before the project scope can be fully determined. The designer should document the decision making process, including the evaluation that led to the selection of the preferred alternative(s).

The scope of work that is defined for an alterations project should reflect pedestrian planning and analysis for accessibility/usability that is commensurate with the overall roadway design work effort.


Let's use the classic 4Rs of highway design to illustrate how establishing the scope of work relates to access planning (see Appendix for TxDOT's definitions). Most 4R projects involve roadway pavement, although many other elements of construction can also be included:

1. Reconstruction

Reconstruction of roadway facilities is an ambitious undertaking of comprehensive scope under which most objectives can be fully realized for both roadway and sidewalk design. Projects of this complexity should be able to meet or exceed minimum accessibility criteria.

Example: A 1.5-mile length of residential street was reconstructed and re-aligned and water, fire hydrant, and sanitary and storm sewers rehabilitated as part of the project. New curbs and gutters were provided throughout. Accessibility features included new aligned curb ramps with detectable warnings at all crossings. Sidewalks were replaced and driveway aprons reconstructed where needed to meet cross slope limits.

2. Rehabilitation

Rehabilitation projects typically raise subgrade issues. Feasibility is a factor here and ‘work-arounds' will require case-by-case design solutions.

Example: Storm drainage improvements (new inlets) are planned for one side of an existing developed streetscape. Sidewalk and roadway surfaces and subgrade facilities are removed at each corner, but the sidewalks they connect to will remain. When sidewalk segments are replaced or repaired, the new work must provide accessibility/usability. But it must also meet the grades of existing sidewalks at the project boundary. Providing intermediate transition segments between the new and existing work (rather than matching the old) will serve users best. Future work then need only improve the transition segment and the existing sidewalk. In addition, the scope of work for this alteration must include new curb ramps (and the improvement of existing ones, as feasible). The agency should consider adding opposite-side curb ramps to the scope of work, as well.

3. Restoration

Restoration projects return pavement structure, riding quality, or other roadway characteristic in an existing cross-section to near-new condition. Because the work affects the usability of the surface, it is considered an alteration and must include curb ramps at pedestrian crossings.

Example: An existing rutted roadway surface will be restored. Subgrade structure will be improved and a new surface added without disturbing adjacent existing sidewalks. Curb ramps added in an alteration of this limited scope will be usable by many, but may not be optimal in location, wayfinding, slope, width, or other feature until a later alteration to the sidewalk is undertaken.

4. Resurfacing

Most resurfacing will be viewed as an alteration—a change that affects surface usability. However, spot patching and liquid-applied seals are described as maintenance not requiring curb ramps in DOJ technical assistance publications. FHWA guidance distinguishes between structural and non-structural resurfacing.

Temporary Routes

Interim pedestrian accommodations put in place as part of a temporary traffic control plan are considered alterations subject to the ‘maximum extent feasible' limit in the standard. The Manual on Uniform Traffic Control Devices (MUTCD) includes detailed requirements on maintaining pedestrian access through or around a work zone. Project planning must include a temporary usable route that provides the accessible features of the disrupted route, perhaps even including APS.

Resources: MUTCD Chapter 6 at:
ATSSA work zone safety grant at:

Identification of Constraints and Opportunities

An on-the-spot survey of existing development at the project location is the first step in identifying physical constraints that may require work-arounds or feasibility assessment. There will be a need to evaluate the pedestrian route with respect to width, setback, running grades, cross slopes, lateral and vertical clearances, and sidewalk appurtenances and to identify opportunities to work with the current grade or make use of the parking lane or roadway space, tighter corner radii, and other potential sources of flexibility.

FHWA has developed an inventory process to document existing sidewalk conditions that includes forms and checklists for field information to aid in project scoping, analysis, and design. The forms can be adapted to meet the needs of a particular agency and will be particularly useful in project planning. Because the survey forms do not include pedestrian signalization considerations, agencies adapting its format for local use should add the APS criteria outlined in the NCHRP 3-62 report posted to the website of the Pedestrian and Bicycling Information Center. A separate chapter addresses retrofitting an intersection with APS.

Resources: Sidewalk Inventory Form, in ‘Designing Sidewalks and Trails for Access' at:
APS criteria in NCHRP 3-62 at:

Complex engineering design utilizes topographic, elevation, and geometric design information for the design of curb ramps, landings, slopes, clearances, and signal locations in a substantial project. It is important that such surveys include entrance elevations for abutting facilities. Many agencies use an inexpensive rotating laser for this purpose. An electronic level can pinpoint excessive slope and cross slope locations.

During the site design survey and pedestrian route assessment for an alteration project, carefully identify any condition that is likely to affect route accessibility. Examples of existing infrastructure elements that may influence project planning include drainage structures, manholes, utility poles, sewers, water mains, and underground conduits and vaults. In narrow rights-of-way, street trees, building entrances, and basement extensions from adjacent buildings will limit design flexibility unless relocation has been included in the project scope.

Development of Alternatives

When the designer is faced with constraints that affect conformance with accessibility objectives, alternative designs need to be developed and assessed. Chapter 5 addresses accessible design alternatives under a wide range of existing conditions.

Project Documentation

It is common practice in all project designs to document the analysis of certain problem types, including a description of the alternatives considered and decisions made. A street pavement thickness design, for example, will consider the bearing soils, the future truck traffic loads, pavement type, amount of excavation, cost of pavement materials, and other variables. The final selected pavement thickness will be justified by this analysis of relevant variables and their effects on each other. The engineering judgment(s) that lead to the final decision are documented and become part of the permanent project record.

For alteration projects where some improvements may fall short of new construction standards, documentation is very important. The structural design of a bridge includes a very careful analysis of all the components to assure that the bridge will not collapse and cause injury or death. This same standard of care should be exercised with respect to accessible design. Documentation reveals the standard of care that guided engineering judgments made in the course of the work. In the event of a challenge at a future time, documentation can be retrieved from project archives in support of the agency's decisions.

Photo of residential neighborhood showing new sidewalk and curb ramp construction.

This reconstructed residential street in Ohio curves through several intersections skewed by as much as 30 degrees. Although aesthetically pleasing, this posed some design challenges for accessibility. As can be seen in the photograph, low retaining walls were required on many corners. The project included new water mains, fire hydrants and services, sanitary and storm sewer rehabilitation, new curbs and gutters, driveway entrance replacements (to allow ADA-compliant sidewalks across the driveways), and full-depth street reconstruction for approximately 1.5 miles of suburban streets. Paired curb ramps with detectable warnings were constructed at all intersections.

Example: As part of a SR25, several existing sidewalk segments will be connected through a small neighborhood commercial area. A tree of substantial caliper shades a 30-inch-wide sidewalk; a retaining wall occupies the property line. The two-lane roadway is also narrow and provides no parking lane. Providing an accessible crossing to a more generous sidewalk on the other side of the street may be an acceptable solution in this instance if the pedestrian crossing is improved and safety considerations are addressed. Alternatively, the town may determine that a preferable course for student safety is to acquire right-of-way and relocate the retaining wall to provide adequate sidewalk width. At the tree, a lesser walkway width (32 inches is the ADAAG minimum for a 24-inch length) can provide the required usability for this limited distance in an existing facility (it wouldn't be an acceptable choice in new construction, however). In the permanent record file for the project, the city engineer should document his efforts to conform to the ADA criteria and his/her decision to build a portion of the sidewalk that is not in strict compliance with new construction standards.

Several state highway agencies have established processes to document infeasibility in a project element or elements under state code requirements or regulations. They offer an opportunity to explain the existing physical or right-of-way constraints that limited conformance to the ADA standards and may be called Design Details of Nonconforming Elements, Design Deviations, Modification of Standards, or other. While useful in the project record, there is no process at the Federal level (where the ADA and Rehabilitation Act are principally enforced) by which review and approval, exceptions, or variances can be granted. For a typical city agency, the designer or the project manager would make the determination of ‘maximum extent feasible', document the engineering judgment that was used in the evaluation of alternatives, and describe the solution that was selected.

The ADA is a civil rights law and by nature it gains clarity through litigation. Careful documentation will not protect against complaint, but evidence of the considerations that led to the specific project solution may be persuasive in court or in discussions with users. Taking a proactive stance towards solving access issues in the right-of-way may allow issues to be addressed and solved without risking a complaint.

Resources: Texas Department of Licensing and Regulation (TDLR) at:
Maryland State Department of Transportation at:
Nashville, TN at:

 Case Study: Photo of retrofitted curb ramp that extends through the width of the gutter.

Case Study—Narrow Sidewalks

  • When this roadway in Washington, DC was resurfaced, existing non-compliant curb ramps were replaced.
  • The counterslope of the brick gutter at the toe of this curb ramp was eliminated in order to extend the ramp through the gutter. This allows the ramp to be shorter, because it meets the crown of the roadway at a higher point.
  • It also eliminates ponding at the toe.
 Case Study: Photo of a parallel curb ramp with detectable warnings in a narrow sidewalk.

Case Study—Typical Parallel Curb Ramp

  • The limited width of the right-of-way along this street dictated the need for a parallel curb ramp.
  • Detectable warnings are shown along the leading edge of the central landing as specified in the draft PROWAG.
 Case Study: Two contrasting photos show a US intersection with space-consuming flared curb ramps compared with an intersection in Barcelona, Spain, where the sides of the ramps are shielded from pedestrian travel by poles or trash cans, leaving more sidewalk area for pedestrians.
Case Study: Two contrasting photos show a US intersection with space-consuming flared curb ramps compared with an intersection in Barcelona, Spain, where the sides of the ramps are shielded from pedestrian travel by poles or trash cans, leaving more sidewalk area for pedestrians.

Case Study—crowded corners

  • This urban corner is crowded with existing signal poles, signal boxes, and utility boxes that limit curb ramp design and placement.
  • One solution, shown in the first photo: reduce curb radius to maximize available corner area and ease flares to fit the available space. Still needed: detectable warnings.
  • Another option, shown in lower photo: shield ramp sides against pedestrian travel with pedbutton poles and sidewalk furnishings. By eliminating the flares, more corner area is gained. Bonus: returned curb offers useful wayfinding cues for non-visual travel. Note that the curb ramp here is the full width of the crosswalk, another pedestrian benefit. This example is from Barcelona, Spain.