Warren Forensics

Stairs that contain three or fewer risers are considered short flight stairs according to safety standard ASTM F1637-21: Standard Practice for Safe Walking Surfaces. Single step transitions are also considered a short flight stair. Short fight stairs can be particularly hazardous for pedestrians due to the lack of visual cues signifying an elevation change. Unexpected changes in elevations can cause pedestrians to misstep and fall.

For example, a woman visited a friend’s home for the first time. While walking from the entryway into the living room of the house, the woman fell down a single step transition and sustained significant injuries. This home had a “sunken” living room that decreased in elevation approximately 7 inches from the entryway. Both the sunken living room and entryway consisted of similar wooden flooring.

An example of a single step transition within a residential home.

The woman failed to accurately perceive the elevation change between the entryway and the living room due to a lack of visual cues causing her to misstep and fall. Missteps occur when the pedestrian puts their foot down on the walking surface incorrectly due to a misperception of the walking surface depth. The nosing to the elevation change was inconspicuous and visually blended with the flooring of the living room below. The woman did not perceive the depth change of the single step transition, incorrectly placed her foot, lost her balance and fell.

In order to prevent injuries on short flight stairs, ASTM F1637: Standard Practice for Safe Walking Surfaces recommends that short flight stairs be eliminated wherever possible. If the elevation change cannot be made flush, then the short flight stairs should be converted to a ramp that complies with ASTM F1637 and applicable building codes. ASTM F1637 recommends that “obvious visual cues shall be provided to facilitate improved step identification. Handrails, delineated nosing edges, tactile cues, warning signs, contrast in surface colors, and accent lighting are examples of some appropriate warning cues” in areas where short flight stairs already exist and cannot be removed or converted to a ramp.

An example of short flight stairs with high contrast delineated tread nosing to aid in pedestrian depth perception.

It is important to provide enough visual cues to the pedestrian to signify that there is a short flight elevation change. Here, the visual cues such as handrails, delineated nosing edges, tactile cues, warning signs, contrast in surface colors, and accent lighting help draw the pedestrian’s visual attention to the elevation change and provide information about the depth of the elevation change. With sufficient visual cues, the pedestrians will be able to accurately perceive the elevation change while walking and avoid a misstep and fall.

Ellen Szubski, Ph.D., CXLT, CPSI, AHFP, is the senior human factors consultant at The Warren Group. She earned a Doctorate of Philosophy in Human Factors Psychology and a Master of Science in Applied Psychology from Clemson University.  She did her dissertation on “The Influence of Pedestrian Biological Motion on Time-To-Collision Estimates at Night”.  She is also a Certified XL Tribometrist, Certified Playground Safety Inspector and a Certified Associate Human Factors Professional (AHFP). Prior to entering the forensic field, Ellen planned and conducted experiments for a major bicycle manufacturer. She also conducted laser strike perception studies for the Department of Defense.  Ellen applies her experience in Human Factors to the analysis of crash investigations and other personal injury matters. These matters often include collisions involving vulnerable road users and drivers, driver distraction, and slips, trips, and falls. She utilizes her knowledge of OSHA regulations, codes, and standards in her analysis of premises liability incidents and safety consulting.  Ellen is a current member of the Human Factors and Ergonomics Society (HFES) and it’s Forensic Professional Technical Group.