The use of laser scanning as a method for measuring stairways following an accident

Stairs present significant potential for harm to their users. A fall on stairs, particularly in descent, often leads to serious injury or even death. The authors have been involved in the investigation of many workplace stair accidents. Proper forensic investigation into the cause of a stair accident has often found the incident to be wholly or partly caused by poor stair design. In order to establish the relationship between the stair design and a given fall, an onsite survey has to be conducted, determining the rises and goings along with other key dimensions. The Health and Safety Laboratory (HSL), Buxton, UK, regularly undertake this type of survey using a digital inclinometer, a steel rule and a tape measure. Laser scanning is an emerging technique that is now accessible to the surveyor to complement or replace traditional approaches. The laser scanner and associated software produces a dense point survey in 3D, allowing dimensional analysis of the features. The authors used both traditional and laser scanning techniques to study the scenes of two fatal stair falls. The analysis presented allows the suitability of laser scanning for stair-fall investigation to be considered. Identification and classification of errors are needed in order to consider if the error is acceptable or can be mitigated. Laser scanners are impressive instruments providing data from which can be used to create a virtual 3D environment that can be used to reconstruct and explain an event and contributing factors. The use of both survey methods currently provides the investigator with complimentary data that allows accurate measurements to be presented in the context of the three-dimensional environment.