Slips, trips and falls in outdoor environments can be caused by rain, sleet, ice and snow, and particulate soil that causes surfaces to become slippery or produce poor traction. While we cannot control environmental conditions that increase slipperiness of outdoor walkway surfaces, we can certainly reduce the likelihood of falls through improved design of exterior sidewalks, curbs, parking areas, improved lighting, and improved maintenance to increase awareness and eliminate hazards.

This reference note addresses slip, trip, and fall hazards, and describes interventions, including outdoor walkway design and maintenance, visible warnings, and snow/ ice removal strategies. Walkway surfaces include sidewalks, curbs, parking areas, curb ramps, and entrances. Stairway design is not addressed in this reference note. See LP 5158, Controlling Falls on Stairways, for guidelines on stairway fall prevention.

Trip Hazards

A trip occurs when the foot strikes a near-ground obstacle that abruptly arrests the movement of the food when the body’s center of gravity is in motion.  This causes the center of gravity to rapidly move out of the area of the body’s support base (the planted foot), resulting in a fall.  A trip most often results in the person falling forward, while a slip most often results in the person falling backward.

Most state, local, and federal codes and standards describe changes in level of ¼ inch or higher in the course of travel as a trip hazard.  The obstacle should be eliminated through facility design or maintenance, if at all possible.  However, if elimination is not possible, other options include:

•    For changes of level ¼ inch to ½ inch (6mm to 13mm), bevel the edge with a slope no greater than 1:2.

•    Slope is the angle of incline usually given as a ratio of the rise (or vertical height) to the run (or horizontal length).  The larger the run, the more gentle the incline angle.

•    For level changes greater than ½ inch (13mm), install a ramp with maximum slope 1:12.

•    A third, but less desirable option, is to make the hazard visually noticeable through appropriate detectable warnings.

Sidewalks, Curbs and Parking Lots

A business owner may not be responsible for injuries resulting from a fall on a public sidewalk located outside his or her property.  However, some courts may impose liability for injuries on a sidewalk used exclusively by customers coming to and from the business.  Consult with your legal counsel if you have questions on liability.

A parking lot owner, however, can be responsible for maintaining the parking lot in a manner such that it is reasonably safe for people using it.

This includes:

•    Filling and patching cracks and holes

•    Repairing and eliminating raised areas due to tree roots, settling, cold weather (frost heaves), and ordinary wear and tear.

•    Reducing surface water by directing roof drainage away from sidewalks and parking areas.

•    Clearing sidewalk/parking areas of snow/ice before employees and guests arrive.

•    Centering and securing parking stoppers.

•    Painting or staining parking stoppers near entrances Safety Yellow to improve visibility.

Curb Ramps and Handicap Ramps

State, local and national codes specify guidelines/requirements for curb ramps and handicap ramp design.  For example, ramp slopes 1:15 minimum to 1:12 maximum with “slip-resistant” surfaces is often cited.  There are no specific guidelines as to what “slip-resistant” means, but some codes specify grooving or other alternations of the curb ramp to improve slip-resistance.  Check with your state and local codes for requirements on ramp slip-resistance guidelines.  Handicap ramps and curbs are colored Safety Yellow (see section on Color, Contrast, and Visible Warnings).


Entrances represent unique slip and fall issues and are addressed in LP 5408, Preventing Slips and Falls: Selecting the Right Matting System.  For outdoor walkways at entrances exposed to the elements, consider installing a canopy to reduce snow, ice and water from being tracked into the building.

Color, Contrast and Visible Warnings

Recent U.S. Access Board Research recommends Safety Yellow as the preferred color for persons having very low vision.  Yellow or yellow-orange warning surfaces are preferred over black warning surfaces.  Safety Yellow, therefore, is a color standardized for use as a warning in the pedestrian/highway environment.

Ice, Snow, Water

Slips and falls from snow, rain, and ice are common in northern climates.  Falls can be caused by inadvertent accumulation of ice and snow due to misapplication.  Misapplication can be caused by selecting less efficient deicing chemical(s) and friction additives (sand), and inadequately managing application schedules.  Effective ice removal often occurs during the day with full sun.  But, full sun will melt adjacent snow or ice, placing water on the de-iced walking surface.  This will dilute the solution and tend to refreeze at night.  With the dropping temperatures, ice can re-form with the falls occurring first thing in the morning.

Selection of ice melting chemicals

•    Rock salt (Sodium Chloride) is the least expensive but is somewhat corrosive and can damage concrete, interior surfaces, and vegetation.  It may need a wetting agent for application at low temperature.

•    Calcium Chloride and Magnesium Chloride are more effective than Rock Salt, and most effective at lower temperatures.  Magnesium Chloride is somewhat less corrosive than Calcium Chloride, which is about as corrosive as Rock Salt.

•    Calcium Magnesium Acetate is the most environmentally friendly, but is more expensive and is least effective at lower temperatures.

•    The following are guidelines for managing slips and falls from snow, ice and water:

•    Plow, shovel, and use deicing, salting, or ice melting chemicals to remove ice and snow.

•    Pre-apply deicing chemicals before a storm, followed by snow/ice removal during and after the storm.  Use plenty of deicing materials, as using “barely enough” will leave patches of ice.

•    Check the surface regularly.  For parking areas, this can be time consuming, but it is well worth the effort.

•    Aim for evaporation.  If the water can drain (e.g. drains aren’t blocked) and there is full sun, or even reasonable wind, the water (even ice) will evaporate.  A dry pavement is a clear indication there is no ice.

•    Use a friction additive.  Sand is the most popular because it’s cheap.  Use a lot of it.  Make certain that anyone walking on the surface has a lot of traction.  You can clean up the mess once the bad weather is over.

•    Check and treat surfaces every morning, especially around snow piles where melting may have created new problem areas.  Reevaluate during the day and re-treat as needed.

•    Remember that a clean-looking surface is only “safe” if it’s dry.  A wet surface can contain ice, and can also turn to ice in the shade or overnight.

•    Hold facility managers, custodians, grounds maintenance staff, and contracted snow removal personnel responsible for snow and ice removal.

•    Train those responsible in procedures for safely maintaining walkway surfaces, including the location of equipment and supplies.

Outdoor lighting

Inadequate lighting may also lead to accidents involving falls in parking lots, trips over curbing, falls on a step or stairs from a parking lot to a store, and trips and falls due to holes, cracks, and uneven surfaces.

Recommended outdoor lighting levels for general parking, ramps and corners, pedestrian areas, and entrances are giving in LP 628, Lighting for Safety and Performance.

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