With over 8 million people treated for fall-related injuries in 2004, falls are the leading cause of nonfatal unintentional injuries treated in hospital emergency rooms, according to the All Injury Program, a cooperative program involving the National Center for Injury Prevention and Control, the Centers for Disease Control and Prevention and the Consumer Product Safety Commission. A combination of deficiencies in design, lighting, visibility and attention are usually the culprits in stairway slips, trips and falls.
To help reduce these accidents in your operation, outlined below are recommendations for safer stairway design, maintenance and use.
Riser and Tread Design
Research has shown that during stairway use, pedestrians view only the first and last three steps, with the rest of the stairway negotiated without looking. Therefore, design of the top three and bottom three steps is very important.
More serious upper and/or lower extremity injuries occur when traveling down a stairway than when traveling up a stairway. In stairway descent, the tread depth – or horizontal surface – must be adequate for the ball of the foot to land on the tread without extending over the step below. If not, an over-step or misstep can occur, causing a fall forward. Trips and falls that occur during stairway ascent are often attributed to variation in riser, or vertical surface, height.
The current recommendations for riser and tread dimensions state that:
- All tread and riser dimensions should be uniform throughout the entire stairway. Most building codes require risers not to vary more than 3/8 of an inch between the tallest and the shortest riser within a given flight of stairs;
- Riser heights should be 4 inches (10.2 cm) minimum and 7 inches (18.0 cm) maximum. Minimum tread depth should be 11 inches (28.0 cm), exclusive of overhang;
- Tread surfaces and floor surfaces leading to the stairway should be slip-resistant;
- Stairways with more than 12 steps should have an intermediate landing. Landings should be void of any raised areas or trip hazards.
Poor visibility of both risers and treads can lead to misreading the stair edge, which can cause faulty foot placement and an accident. To increase visibility:
- Provide visual contrast on tread nosings, or at the leading edges of treads without nosings, so that stair treads are more visible for people with low vision. Surfaces colored safety yellow are the “most visually detectable,” according to the U.S. Access Board Research.
- In low light areas, highlight each step using step lighting. Additional lighting guidelines are found below.
- Post signs calling attention to the stairway at waist height on the approaches from both directions.
A good example of why visibility matters comes from a restaurant chain that experienced a rise in general liability claims from customer slips and falls. Working with an insurance loss prevention consultant, restaurant corporate management surveyed facility conditions, including stairways, in a number of restaurants. The survey results showed that poor lighting for the stairways in the various locations was a significant exposure and that the restaurants needed maintenance programs for tread conditions and secure handrails.
Based on the survey results, the company reduced their slip-and-fall risk by adhering reflective safety tape to all stair treads and installing track lighting and stair riser lights wherever possible. Additionally, each restaurant instituted a self-audit program to maintain appropriate safety goals and added a stair condition checkpoint to the outside food inspector’s audit form. In the 7 months following these actions, the restaurant group has experienced only two falls on stairs.
Stair Rails and Handrails
Stair rails and handrails are needed for very different purposes. Stair rails, or stair guardrails, protect pedestrians from falling off the edge of the stairs or landings while handrails help pedestrians keep their balance and provide leverage when ascending/descending stairs. Here are some recommendations for stair rails and handrails to reduce slip-and-fall injuries:
- Install a two-rail system; a top rail at 42 inches (106.7 cm) high and a second handrail at 34 inches (86.5 cm) minimum, and 38 inches (96.5 cm) maximum, vertically above stair nosings.
- Protect the open area under the top rail to the steps by installing a fixed barrier. Fixed barriers are preferred to balustrades in public areas. Check code requirements before installing balustrades.
- Midrails, screens and mesh are recommended between the top rail and stairway steps for stairways used during construction.
- Lack of, or improperly positioned and designed, handrails often are cited as proximal causes of stairway falls. Well-designed handrails not only can reduce the chance of a fall, but may also serve to limit the distance down the stairs one falls.
- Install highly visible handrails on both sides of the stairs.
- Handrails should be at a consistent height above stair nosings, ramp surfaces and walking surfaces. Top of handrail gripping surfaces should be 34 inches (86.5 cm) minimum and 38 inches (96.5 cm) maximum vertically above the stair nosing (see Figure 1.).
- Handrails should allow continuous holding (gliding above) without encountering support obstacles.
- On the upper floor surface, the handrails should start out horizontally, at the beginning of the demarcation zone (about 12 inches before the first step). This gives people one more visual cue to the stairway’s presence and allows them to grip the railing before they begin to descend the stairs.
- At the bottom of the stairway, the handrail should continue horizontally beyond the bottom step for a distance at least equal to the depth of one tread.
- Handrails with a circular cross section should have an outside diameter of 1.25 inches (3.2 cm) minimum and 2 inches (5.1 cm) maximum.
- Handrails with a non-circular cross section should have a perimeter dimension of 4 inches (10.2 cm) minimum and 6.25 inches (16.0 cm) maximum, and a cross-section dimension of 2.25 inches (5.7 cm) maximum.
- Clearance between handrail gripping surface and adjacent surfaces should be 1.5 inches (3.8 cm) minimum.
- If the stairway is two or more lanes wide, install intermediate railings in the middle to make the stairway more noticeable and to help people avoid or correct missteps.
- New stairways greater than 75 inches should have intermediate handrails so that handrails are within 30 inches of all portions of the egress route.
- Open stairways or stairways with open risers may not be permitted. Check your local building codes.
As people descend a stairway, the floor below and the treads are in their line of sight, but the risers are not. Therefore, the top safety priority is to make the treads more visible through contrasting nosings and adequate lighting.
Install at least 20 foot-candles (200 lux) of local spot or floodlight illumination to highlight the stairway and the floor approaching it on both levels. Measure the illumination at the applicable floor or stair tread surface. Make sure the edge of each tread is properly illuminated, and aim the lighting so that shadows are not cast on the stairway and glare does not disrupt the vision of those approaching the stairway.
Ensure that stairways are lit at all times. Back-up power is especially critical for stairway lighting.
A significant number of “air step” falls – stepping off the top of a stairway into air – occur on low stairways that consist of one, two or three steps. In effect, people step off into thin air, not having seen the stair or stairs at all. Commonly found inside public buildings such as hotels and restaurants, “air step” falls occur because people fail to perceive the modest change in floor level and are usually the most serious accidents on low stairways.
Tripping also is a hazard, especially when people don’t notice the stairway as they approach from the lower level. Though failure to detect the presence of low stairways is the biggest reason for such falls, inadequate stair dimensions, missing railings, improper railing heights and poor lighting also are contributing factors.
If it is feasible from an operational and a financial standpoint, consider the following for low stairways:
- Change the stairway approach path to require people to slow down and turn about 5 to 10 feet (1.5 to 3 meters) before reaching the stairway. This type of approach makes it more likely that people will notice the stairway.
- Use railings and other assistive fixtures to achieve a right angle or oblique turn.
- Remodel the stairway into a ramp.
- Visually contrast the leading edge of each step using safety yellow.
Maintenance and Use
Many stairway accidents occur due to poor maintenance, inattention and use. Keep stair treads clean and in good condition. There should be no excessive wear, missing treads or loose treads. Carpeted stairs should be in good condition with no noticeable deterioration. Never use stairs for storing objects. Do not carry items in the hands on stairs, and do not rush up or down stairs.
Finally, address importance of stair safety in employee safety training sessions.
In 2003, slips and falls accounted for more than 17,000 deaths in the United States, according to the National Safety Council. The council’s data also shows that incidents of falls start to steadily increase when people reach 40, which is a significant concern for employers given the trend in employees working long beyond traditional retirement age. Therefore, designers, builders, owners and employers should take the necessary steps to reduce risk as much as possible.
Wayne Maynard is product director of ergonomics and tribology at the Liberty Mutual Research Institute for Safety, and George Brogmus is technical director, Ergonomics, Liberty Mutual Group’s Business Market.