|Version 4.0 July 9, 2001||
|Basics of Accessible Design||© Edward Steinfeld and Danise Levine, 2001|
|Contents||4. Building Circulation|
The accessibility of circulation systems determines the over-all extent of access that can be attained in a building; therefore, these parts of buildings are given high priority in code reviews for barrier-free design. Yet, there are a number of issues in the design of circulation systems that even codes don’t address adequately. Understanding these issues can help architects approach universal design from a more informed perspective.
Clearances in front of doorways are just as important as the clear width of doors. Minimum clearances for wheelchair access are based on the direction from which a door is approached. Requirements for both corridor and latch side clearances are found in most accessibility codes. Research has demonstrated that a clearance of 24 in. or more should be provided at the latch on the pull side of doors if they are approached from a forward position. At least 5 feet of corridor clearance is needed in front of such doors. Most current codes require only an 18 inch latch clearance. This should be increased where possible to insure that people with severe disabilities can use the door. If doors are approached from a parallel direction rather than forward, or from the push side of the door, the 5-foot clearance in the direction that the door swings can be reduced. Doors in alcoves should be treated as forward approaches since wheelchairs must be positioned that way in order to open such doors. Sometimes doors are set back from the face of the wall several inches. A recessof up to 8 inches is considered acceptable before it is defined as an alcove. Many wheelchair users must use a forward approach with doors having closers as well. Although codes don’t address it, thresholds at doors are very difficult for many wheelchair users to negotiate. As a rule of thumb, the clearances around any door that has a threshold should be designed for a direct forward approach. Sometimes latch clearances in front of doors can be reduced with little impact on accessibility, for example, at entries to patient bedrooms in acute care health facilities where doors are 48 in. wide and usually held in the open position.
The most burdensome door maneuver for wheelchair users is approaching from the push side and the hinge edge parallel to the plane of the doorway. This requires pulling the door open while maneuvering around it. This maneuver takes up a lot of space. Ideally, doors should be designed to avoid the need for this approach by locating the latch at the side from which people approach or providing enough space to make a forward approach.
People who use walking aids (canes, crutches and walkers), those who have low stamina, those with impairments of reach and grasp and those with visual impairments also encounter difficulty with doors.
Individuals who use walking aids often have difficulty pulling a door closed behind them because their walking aid gets in the way of the door as they pull it closed. It is also difficult for many to open a door with a closer and still maintain good balance because they must push against the door while moving through it.Individuals with visual impairments can be injured at the pull side of doorways with lots of traffic if doors do not have a vision panel.
One of the most important and difficult doorway issues for many people with disabilities is the force required to open a door with a mechanical closer. By the laws of physics, the opening force of the door must always be greater than the closing force of the closer unless automation is introduced. A large proportion of people with disabilities cannot exert very much force upon a door. One research study that examined such abilities found that only 23-30 per cent of wheelchair users tested and 39-44 percent of people with other disabilities could exert forces greater than 15-pound force in one of several different directions. Yet 15-pound force for closing a door is the minimum required for many doors by fire codes. This means that the opening force will far exceed 15 pounds.
Door closer manufacturers claim that a 15-pound minimum opening force should be required for doors to ensure that they will close properly and safely under difficult conditions, such as those found during fires and at windswept entries. If lower forces are used, other actions must be taken to keep doors closed where severe conditions exist. For example, wind can be blocked by wind screens, or its impact reduced by careful orientation of doorways. On the interior, not much can be done about lowering required minimum closing forces for fire safety without causing serious problems. Lower forces may not insure adequate latching or may allow faster spread of fire through doors that are forced open by air pressure due to the increased heat. Magnetic hold-open devices can be used to eliminate the need to open doors on an everyday basis while still insuring proper closure during emergencies.
When all efforts to reduce closing force of doors that must remain closed during everyday use fail, the only alternative is an automatic door. Full powered automatic doors are quite costly, but most manufacturers make “low-energy,” slow-moving, automatic door openers. They can be activated manually by push buttons rather than automatically by mats or photo-electric sensors. Guard rails are not required for these doors. Some of them are designed specifically for accessibility retrofits and are much less costly than conventional automatic doors. Low energy doors open and close very slowly so one can often observe many people without disabilities using the door after a person has activated it. Many of these doors can be used manually as well as automatically which reduces energy losses caused by the slow operation.
On interior doors, compressed air systems can be used to power mechanical closers. Controls mounted on the door release the pressure for opening but re-apply it for closing. Such systems are available for multiple door applications.
A few state building codes now require automated doors wherever the opening force of doors at entrances exceeds 15 lbs. As a general good practice of accessible design, every publicly used building should have at least one automated door,e ven though not required by codes.
Hallways and Corridors
At any dead end, there should be space for people in wheelchairs to turn 180 degrees. A minimum-sized space for this maneuver is 60 in. in diameter, but a space 60 in. by 78 in. is much more convenient, particularly for older people who have limited range of motion and strength in their arms. The turning space can be T-shaped as well. The turning space should be measured at the floor. Objects overhanging this clear floor space (counters, lavatories, etc.) will not obstruct turning a wheelchair as long as they do not project over it more than 19 in. and their underside is at least 27 in. high. These dimensions provide a knee clearance under the object.
As on sites, overhanging and projecting hazards must be eliminated from buildings. A common problem is the projecting water fountain or fire extinguisher. Another, even more serious hazard is a cantilevered intermediate stair landing. Such structures are often found in open lobbies and other circulation spaces where they are completely unexpected to the non-visual building user. Falling hazards such as stairs leading down directly in the path of travel and loading docks should be either eliminated or protected with curbs, railings or other devices. In rail stations, the edges of loading platforms should be marked with a contrasting color and texture to warn people with visual impairments. Many transit systems employ flashing warning lights to warn everyone of an approaching train. This visual warning is important for people with hearing impairments. Transit systems are increasingly adopting a full or partial barrier between the platform and the track area. Technology is now available to automatically dock the train in the exact same position allowing the doors of the train and the doors of the platform barriers to be lined up. This system not only insures against accidents by visually impaired and hearing impaired individuals, it also prevents suicides.
In existing buildings, there is less freedom to alter the plan. There are four basic approaches to increasing accessibility that can be used alone or in some combination.
Moving offices, classrooms and other duplicated facilities onto an accessible floor can eliminate the need for mechanical transport. This solution is acceptable as long as the accessible facilities are of similar quality and provide the same opportunities or resources as the inaccessible facilities.
Installing a ramp can sometimes overcome small differences in elevation. However, it is often not possible to install ramps because they need a large amount of space. Moreover, ramps are just as much of an obstacle to some people with disabilities as are stairs, particularly if they are steep. In fact, most wheelchair users will have great difficulty negotiating ramps connecting levels more than one story high because of the energy expenditure involved.
The potential and feasibility of using separate entrances to serve different levels should be investigated. This is not acceptable when spaces in a building are related in use, and individuals or groups must move quickly and conveniently from one to another. It may be appropriate in buildings that receive only periodic use by the public and where movement between different areas is minimal or non existent. It is more appropriate in moderate climates, or in very large buildings whose different parts are essentially used as separate facilities. However, code authorities may not accept this strategy because it involves judgments about the importance of space relationships.
If the first three alternatives will not work, the only choices left are the addition of a platform lift or elevator. Platform lifts are becoming popular because of their low cost ( usually under $5000) and ease of installation in a small space. Although some lifts now on the market can operate to a height of 20 feet or more, they are more typically used at level changes one story or less.
Architects should carefully evaluate the safety, reliability and convenience of particular products before specifying them. In particular, control systems vary greatly and some are very awkward to use. It is important to work out the specific control needs of the client before selecting the product. Architects should evaluate how successfully platform lifts protect people from these hazards; 1) wheelchairs, crutches, or feet slipping off the platform; 2) jolting people who have difficulty maintaining their balance; 3) entrapment under a descending platform; 4) electrical shocks at outdoor installations; 5) tripping or slipping while mounting and dismounting; 6) crutch tips getting caught in a gap between the floor level and the platform; 7) structural or mechanical failure which may cause the platform to tip or fall; and 8) undersized platform that requires footrests to hang over the front edge. Design of the area surrounding a lift installation can be as critical for safety as the lift itself. The addition of precautions like the construction of guard rails and fences to keep children out from under the device and rain and snow protection should be considered depending on the installation.
Installation of elevators is sometimes considered a last resort because of cost. However, in many cases, the larger benefits to be obtained by all building users make elevators a better choice than other alternatives. They can increase the value of rental space on upper floors, make such space more suitable for providing services to the public and generally increase the flexibility in use of upper stories.
Several manufacturers produce low cost vertical “residential lifts” that can be installed in certain types of buildings. Technically, they are not elevators but they work in a similar manner and can serve the same purpose in small buildings. These lifts do not have automatic doors equipped with standard safety features. Doors are either manual or use slow-opening automatic openers.
The smallest sized passenger elevator found in public buildings has a 2000 pound capacity. The elevators of this capacity can obtained with interior platform sizes of 68 in. wide by 54 in. deep (measured to the inside face of the door). This size is large enough for a wheelchair to turn around inside the cab and its rectangular space is more efficient for unloading. However, turning a wheelchair around is not always necessary. If there are other people in the elevator, it is usually impossible anyway. Wheelchair users will often back into an elevator in order to be in position for quick egress when they reach their floor. A platform size of 36 x 48 in. is large enough for a wheelchair to be backed into the cab and provides enough space to reach controls.
Elevator doors and the location of hall call buttons must be planned to ensure that slow-moving individuals can gain access to cars before their doors close. Signage, car control panels and car arrival signals must be designed to be usable by people with severe vision and hearing impairments. Most accessibility codes now have requirements for these items. Most codes specify the use of Braille signage in addition to standard alpha-numeric characters.
The use of carpet presents another, yet quite different set of problems. It is known that some types of carpet/pad combinations make propelling a wheelchair almost impossible and increase the difficulty many people have walking. Other installations seem to cause severe “drift” of chairs to the left or the right. The variety of carpet pile, weave, backing and pad combinations is enormous. There has not been enough research to give comprehensive guidance for selection of carpet, but it is clear that long or high pile, soft cushions and poor installation are all problematic. Even in the absence of data and quantitative criteria, some authorities have been very restrictive in their evaluation of acceptable carpet.
Architects need more technical
information to aid them in the design of entrances and interior circulation.
In particular, performance data on platform lifts would help them
evaluate these low cost alternatives to elevators and ramps. In addition,
data on slip-resistance of floors and accessibility of carpets is
necessary before anything but crude discriminations can be made among
Accessible circulation is not just for people with disabilities. Designers should realize that making circulation accessible is a basic issue in building design. Accessible circulation can increase safety, satisfaction, marketability and productivity for everyone. Often, in new buildings, accessible circulation is created by a “separate but equal” approach. A ramp may be installed perpendicular to stairs; there may be an elevator around a corner while the main circulation route is more direct by escalator; the elevator may be located at the opposite side of the building from a principal entry. While these solutions may be necessary in older buildings, in new buildings, they stigmatize people with disabilities and inconvenience both them and the (temporarily) able bodied population because they make the most convenient form of circulation harder to use. The ideal approach is to make the accessible circulation the basic system that everyone uses. Elevators should be in the same location as stairways and serve as a choice for everyone. That is true universal design.