Bus accessibility is not an afterthought but a set of requirements that influence the layout of the floor, suspension, and passenger compartment. A low entry height, space for a wheelchair, or the ability to lower the vehicle at a stop all stem from specific dimensional and functional requirements. That is why accessibility should be considered as early as the vehicle concept stage, rather than only during interior design.
A systematic approach allows for the early detection of conflicts between accessibility requirements and other bus functions, such as the powertrain, battery layout, or number of passenger seats. This is particularly important for manufacturers and integrators of Class I city buses, which must meet the accessibility requirements specified in Annex 8 of UN Regulation No. 107.
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The low floor changed the bus’s design because the effort to lower the floor and the entry height affected the placement of the axles, drivetrain components, and chassis. In Class I buses, the height of the first step from the ground at at least one door generally cannot exceed 250 mm. The regulations also provide for an alternative of 270 mm at two door openings – one for entry and one for exit. The height of the steps in the corresponding passageway and along the entire length of the aisle must not exceed 200 mm.
UN Regulation No. 107 defines a low-floor vehicle as a Class I, II, or A vehicle in which at least 35% of the area available to standing passengers is a step-free zone and includes access to at least one service door. In practice, this requires careful planning of the layout of the axles, the engine or electric motors, the battery, the wiring harness, and other chassis components, while maintaining the required structural rigidity.
This presents a direct design trade-off: lowering the floor reduces the space available for some drive and chassis components. Therefore, the entry height should be determined in conjunction with the drive architecture and the layout of the main components, rather than treated as a parameter set at the end of the design process.
Kneeling is a system that allows the body to be lowered in a controlled manner relative to its normal driving position. This reduces the height difference between the bus entrance and the bus stop. In low-floor vehicles, kneeling may be used to meet entry height requirements, whereas a retractable step cannot be used for this purpose.
The kneeling system must also prevent the vehicle from traveling at speeds exceeding 5 km/h when it is below its normal driving height. This means that the body lowering function must be integrated with the vehicle’s control system. The extent of the lowering, however, depends on the specific solution used and should be determined based on the suspension manufacturer’s documentation.
A comparison with older high-floor buses clearly illustrates the scale of these design changes. In a modern low-floor bus, the entry height and the ability to further lower the body are critical factors for accessibility; therefore, they must be considered alongside the axle configuration, vehicle weight, suspension, and control systems early in the design process.
The bus interior supports accessibility through an appropriate layout of aisles, priority seating, space for wheelchair users, and the placement of handrails, grab bars, and signage. In Class I buses, UN Regulation No. 107 requires at least four priority seats for people with limited mobility. The requirements also cover the space around these seats and their accessibility from the appropriate doors.
Handrails and grab bars must provide a secure grip, have a non-slip surface, and offer adequate visual contrast with their surroundings. Current requirements also specify parameters for their placement and construction. Priority seating itself should be properly marked and visually distinguished from standard seats.
Another important aspect of accessibility is the space designated for wheelchair users. The regulations specify a space for each anticipated wheelchair user that is at least 750 mm wide, 1,300 mm long, and 1,400 mm high. They also require ensuring unobstructed access from the appropriate door to this space, without steps or other obstacles that hinder maneuvering.
For passengers, many of these solutions may be nearly imperceptible, but their dimensions and layout result from detailed requirements regarding accessibility and ergonomics. During the design process, it is also advisable to verify the interior using 3D models and reviews that take into account users of varying heights and mobility levels.
It is advisable to engage an engineering partner when the project extends beyond a single technical area– for example, when developing a new platform, transitioning from an internal combustion engine to an electric or hydrogen powertrain, or modifying an existing model. Changes to the door layout, vehicle length, or floor configuration simultaneously affect the body, powertrain, electrical systems, and control systems. The same applies to solutions such as low-floor design, kneeling, ramps, or interior layout – a decision made in one area often requires changes in others.
Endego supports bus manufacturers in areas such as body and interior design, pneumatic and hydraulic systems, cooling and heating systems, and electrical architecture, as well as in the integration of electric and hydrogen powertrains. Design assumptions can be verified even before a prototype is built using strength analyses, CFD simulations, and, in the case of electric buses, EMC simulations.
This approach allows the bus to be viewed as a single system and enables the early detection of potential conflicts, such as those between the low floor, battery layout, and the routing of high-voltage harnesses. A partner’s support can also be particularly useful when the resources of a company’s own R&D department are limited, and the project, tender, or certification schedule leaves little time to spare.
The earlier a partner is brought on board, the greater the opportunity to optimize the vehicle architecture without costly changes in later stages of the project.
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