36 CFR Part 1192 Americans with Disabilities Act (ADA) Accessibility Guidelines for Transportation Vehicles (2016 Non-Rail Vehicle Guidelines) - Preamble

Running Slope of Ramps Deployed to Roadways or Curb-Height Bus Stops

In the 2010 NPRM, the Access Board proposed to simplify and update the existing guidelines addressing the running slope of ramps in non-rail vehicles by establishing a single standard – 1:6 maximum (17 percent) – for ramps deployed to roadways or to boarding and alighting areas without boarding platforms (i.e., curb-height bus stops). See 2010 NPRM, T303.8.1.⁷ The Board proposed these changes for two primary reasons: to address concerns about the safety and usability of ramps when deployed at the steepest maximum slope permitted under the existing guidelines (1:4); and to update ramp slope requirements in light of the evolution of bus and ramp designs in the 25 years since the existing guidelines were promulgated. The Board’s proposed 1:6 maximum ramp slope engendered the largest volume of comments of any of the proposed regulatory changes in the 2010 NPRM. Commenters overwhelmingly acknowledged the need to modernize the Board’s existing guidelines for vehicle ramp slopes, but expressed differing views on the best approach for their revision. For the reasons discussed below, the final rule retains the proposed requirement that ramps in non-rail vehicles must have running slopes no steeper than 1:6 when deployed to roadways or boarding and alighting areas without boarding platforms, such as curb-height bus stops. However, the text of the final rule has been revised to make clear that the requisite maximum running slope is a design standard to be measured to ground level with the bus on a flat surface; when deployed to roadways or curb-height bus stops, ramps must have the least running slope practicable under the given field conditions.

The existing guidelines specify a range of maximum running slopes for non-rail vehicle ramps depending on the nature of their deployment. While ramps must generally have the “least slope practicable,” the guidelines go on to specify several different maximum running slopes depending on whether the ramp is being deployed to the roadway or to a curb-height bus stop. See 36 CFR 1192.23(c)((5) (ramp slope requirements for buses and vans), 1192.159(c)(5) (OTRB-related ramp slope requirements). When a ramp is deployed to the roadway, the existing guidelines require its slope to be 1:4 maximum. For ramps deployed to bus stops with an adjacent 6-inch curb, the existing guidelines specify a range of maximum ramp running slopes depending on the differential in height between vehicle floor and curb. The existing slope requirements for vehicle ramps deployed to curb-height bus stops are shown in Table 2 below. Running slopes are expressed as the ratio of the vertical rise to the horizontal run.

Table 2 - Existing Guidelines: Maximum Slope of Vehicle Ramps Deployed to Curb-Height Bus Stops

In 1991, when the Access Board issued the existing guidelines for ramp slopes, ramp and vehicle designs were not as advanced as they are today. Standard transit buses had high floors (usually 35 inches above the roadway) and steps at doorways. For this type of bus, lifts are the only means of providing accessible boarding and alighting. Yet, in public transit settings, lifts can sometimes be slow to deploy, costly to maintain, and have reliability issues. These and other factors spurred development and adoption of “low floor” transit buses in the early 1990s. Low floor buses have a lower vehicle floor (typically 15 inches or less above the roadway) that permits a flat – rather than stepped – area at doorways. Most low floor buses also have a “kneeling” feature that hydraulically lowers the front end of the vehicle several inches closer to the curb to aid in boarding. Because of their lower floor and flat entry area, low floor buses can use ramps (instead of lifts) to provide access for passengers with disabilities. These features tend to make boarding and alighting easier and more user-friendly for all passengers and, consequently, reduce dwell times.⁸ As of 1991, however, low floor bus technologies in the United States – as well as related vehicle ramp designs – were still in their infancy. Consequently, the maximum ramp slopes specified in the existing guidelines, while fairly steep for some types of deployments (such as 1:4 to the roadway), reflect what was feasible given then-existing technologies.

In the mid-2000s, when the Access Board initiated efforts to revise and update its non-rail vehicle guidelines, two related considerations prompted evaluation of ramp slopes. First, research studies demonstrated that steeper ramp slopes – particularly ramps with a 1:4 slope – are difficult to use for many individuals who use mobility devices, most notably manual wheelchairs users.⁹ There were also documented incidents of wheelchairs and their occupants tipping over backwards going up bus ramps with 1:4 slopes. Second, low floor bus technologies had rapidly evolved and all major domestic bus manufacturers offered one or more models. Indeed, such buses had increasingly become public transit agencies’ vehicle of choice for fixed-route bus service.¹⁰

In the 2010 NPRM, the Access Board thus proposed to update the ramp slope requirements in the existing guidelines by establishing a 1:6 maximum slope for ramps deployed to roadways or curb-height bus stops. See 2010 NPRM, T303.8.1.¹¹ The intent of this proposal was two-fold: to lessen the steepness of the maximum permitted ramp slope from 1:4 to 1:6, and to simplify application of the ramp slope requirements by replacing the existing deployment-based range of maximum ramp slopes with a single standard. On balance, commenters strongly supported this proposal.

The proposed ramp slope provision received broad support from a wide spectrum of commenters, including the disability community, APTA, transportation researchers, ramp manufacturers, and several transit operators. These commenters applauded the Board’s efforts to simplify the existing ramp slope requirements by specifying a single standard. They also agreed that the 1:4 maximum ramp slope in the existing guidelines was outdated and too steep. A 1:6 maximum for non-rail vehicle ramp slopes, in their view, was safer and more in line with current technology. Nonetheless, some supporters of the proposed ramp slope standard cautioned that, while a 1:6 standard for maximum ramp slope was preferable and generally feasible, certain local conditions (e.g., narrow urban sidewalk, roadside ditch, or excessive road crown) might make achieving a 1:6 ramp slope impractical or difficult in particular deployment situations. These commenters encouraged the Board to consider adding an exception that would permit steeper ramp slopes when necessary due to local conditions. Lastly, several ramp manufacturers observed that 1:6 ramps were commercially available, had about the same total cost of ownership (i.e., purchase price and maintenance costs) as older (1:4) ramp models, and were already in service on thousands of ramp-equipped low floor buses.

Only a handful of commenters expressed outright opposition to the proposed 1:6 maximum slope for ramps in non-rail vehicles. For two transit operators, this proposal proved problematic because, in their view, a single standard cannot adequately take into account the many variables affecting ramp slope under “real world” operating conditions. The third transit operator expressed concern that 1:6 ramps would increase capital and maintenance costs, could require longer ramps, and might not be compatible with some bus or van models. Additionally, two bus manufacturers, while not expressly opposing a 1:6 maximum slope standard, noted that certain models of smaller non-rail vehicles – such as vans or cutaway buses – might require redesign of suspension systems or other vehicle parts in order to achieve the requisite ramp slope.

After the close of the comment period on the proposed rule, the Access Board received reports that a few transit agencies were experiencing problems with the usability of some 1:6 ramp models that had been recently installed on new transit buses. Accordingly, in August 2012, the Board issued a notice that it was reopening the comment period on the proposed rule and planned to hold public meetings in Washington, DC and Seattle, Washington to receive additional information on the new ramp designs. See Notice of Public Information Meeting and Reopening of Comment Period, 77 FR 50068 (Aug. 20, 2012). 

Information developed during the reopened comment period painted a mixed picture of these 1:6 ramps. On the one hand, several transit agencies and individuals with disabilities confirmed that a few new 1:6 ramp models were indeed creating difficulties on some ramp-equipped low floor buses. They reported that, in order to avoid extending the ramps a longer distance outside the bus, some 1:6 ramps were designed with a fixed slope inside the bus and a variable slope outside the bus. The resulting grade break in the ramp run, along with its close proximity to the vestibule area flat floor, caused some passengers who used wheeled mobility devices to have difficulty negotiating the ramps or maneuvering in the bus vestibule (e.g., paying fare or turning into the aisle). Some of the affected transit agencies had taken these ramps out of service, while others were working with manufacturers to develop modifications for in-use ramps. Several commenters, while characterizing the existing 1:4 maximum ramp slope as “unsafe,” nonetheless urged the Access Board to delay issuance of a final rule until research or field testing documented the safety and usability of 1:6 ramps. They noted the complexity of the issue given the interplay of environmental conditions and in-vehicle space constraints.

A number of other commenters, however, expressed support for 1:6 ramps generally, as well as the particular ramp models at issue. Several bus and component manufacturers strongly supported the proposed 1:6 maximum slope requirement, stating that standard and cutaway bus models were already in production that came equipped with ramps capable of achieving a 1:6 maximum slope to roadways or curb-height bus stops. Additionally, a ramp manufacturer observed that, of the thousands of 1:6 ramps already in service on heavy-duty low floor transit buses across several hundreds of transit agencies, only about 2% of transit agencies had cited ramp grade break as a problem. This manufacturer also noted that, by 2013, it expected to have two new, redesigned 1:6 ramp models in commercial production that would address the cited problems by eliminating the grade break in the ramp run and minimizing the ramp’s impact on the available level floor space within the bus at the top of the ramp. Testing of field prototypes was underway, and initial feedback had been positive.

A third group of commenters – including a disability organization and a research institution – believed that the Access Board’s proposed 1:6 maximum ramp slope was still too steep. While preferable to steeper (1:4) ramps, a 1:6 ramp, they noted, was not “user-friendly” and could be difficult for passengers who use manual wheelchairs to use independently. These commenters urged the Board to instead adopt a 1:8 maximum ramp slope, which would make ramps usable for the vast majority of wheeled mobility device users.

Several years have passed since the comment period closed in late 2012. In the intervening years, 1:6 ramps have become well-established in the transit community. The ramp models at issue when the Access Board reopened the comment period have been replaced by a newer generation of 1:6 ramps; these ramps have been on the market – and in use – for several years without generating similar complaints. See Final RA, Section 3.4. Low floor non-rail vehicles equipped with 1:6 ramps are commercially available from a host of manufacturers, ranging from small cutaway buses to large, heavy-duty transit buses. Id. Moreover, the current version of APTA’s “Standard Bus Procurement Guidelines” (commonly referred to as the “APTA Whitebook”), which are widely used by transit agencies throughout the country for their bus procurements, lists 1:6 ramps as the default specification for large low floor buses. See APTA Standard Bus Procurement Guidelines, § TS 81.3 (May 2013). Indeed, 1:6 ramps have become so integrated into the transit marketplace that, at least for the heavy-duty low floor transit buses, these ramps are now the less expensive production models, whereas steeper (1:4) ramps are more costly special order items. See Final RA, Section 3.4.

After careful consideration, the Board has determined that a 1:6 maximum ramp slope – as proposed in the 2010 NPRM – strikes the appropriate balance between usability and feasibility. We believe that establishing a 1:6 maximum running slope for non-rail vehicle ramps will make such ramps more usable for most passengers who use wheeled mobility devices, while also ensuring a workable standard that manufacturers and vehicle operators can meet without undue difficulty or expense. There is near uniform agreement that the 1:4 maximum ramp slope in the existing guideline is outdated and potentially unsafe. A ramp with a 1:6 maximum slope, while perhaps not independently usable by all individuals who use wheeled mobility devices, nonetheless presents a safer and more usable method of boarding and alighting for most mobility device users. Indeed, a recent peer-reviewed transportation study validated the efficacy of 1:6 ramps in reducing ramp-related incidents and accidents on non-rail transit vehicles.¹² This study found that the odds of a passenger using a wheeled mobility device having a ramp-related incident were 5.4 times greater when the ramp slope exceeded 1:6, and the odds of needing assistance were almost as great.

The 2016 Non-Rail Vehicle Guidelines thus require the running slope of ramps in non-rail vehicles used for deployment to roadways or curb-height bus stops to be no steeper than 1:6. However, the text of the provision has been modified to address commenters’ concerns about the difficulty of achieving 1:6 ramp slopes under all deployment conditions.

In the 2010 NPRM, the proposed rule simply established a 1:6 maximum slope for ramps deployed to roadways or curb-height bus stops; the provision did not, on its face, specify whether this maximum applied to a ramp’s designed capability (i.e., ramp must be capable of achieving a 1:6 maximum slope when deployed to the roadway or a curb-height bus stop) or to actual deployments in the field (i.e., ramp cannot be steeper than 1:6 regardless of local conditions under which it is being deployed). See 2010 NPRM, T303.8.1. Several commenters – including some who otherwise supported the proposed 1:6 ramp slope standard – expressed concern that local conditions sometimes make achieving a 1:6 ramp slope particularly challenging or even impossible. These commenters urged the Board to add an exception that would expressly permit steeper ramp slopes when necessary due to local conditions, such as a narrow sidewalk abutting a building in an urban setting, a roadside ditch in a rural area, or an excessive road crown.

To address these concerns, the provisions in the final rule specifying the maximum ramp running slopes for non-rail vehicles (i.e., T402.8 and its two subsections) have been revised to clarify that the specified ramp slope requirements are design standards only. For example, T402.8.1 in the final rule states that, for ramps deployed to roadways or curb-height bus stops, the 1:6 maximum is a design standard that requires such ramps to be capable of achieving this requirement only when the vehicle is resting on a flat surface and the ramp is deployed to ground level. This revision aims to clarify that, although vehicle ramps may be deployed under various roadway and environmental conditions, measurement (and assessment) of compliance with the 1:6 maximum slope requirement is to be taken under one condition i.e., when the bus is on a flat (level) surface, not on a crowned roadway or any other sloping surface. Typically, these ramp slope measurements will be made in the factory or testing laboratory prior to delivery to the field or, after a ramp is serviced, in the transit agency’s maintenance facilities. We believe that these modifications to the final rule text address commenters’ concerns that measurements would be affected by roadway conditions.