Executive summary

Scope and Purpose

The Inclusive Kerbs Phase 4 research project gathered data using a representative example of standard kerbs within a controlled laboratory environment to understand how people with various impairments interacted with them. The study was conducted by Mott MacDonald and Edinburgh Napier University’s Transport Research Institute. It was commissioned by Transport Scotland on behalf of the Scottish Road Research Board (SRRB) and the Department for Transport (DfT). The Phase 4 research is part of the wider Inclusive Kerbs Study, made up of four phases of research.

Phase 1 of the project looked at existing research and found that there are few studies on inclusive kerbs that consider both engineering and human factors.

Phase 2 gathered data on in-situ kerbs and trialled online interview methods to learn more about how people use kerbs. The study considered how kerbs are used for navigating along a street and for crossing the street.

Phase 3 collected data from eleven people with moderate to severe impairments using further online interviews and site visits with volunteer participants. The information gathered from the interviews and from recordings of the participants’ progress at the three visited kerb sites was compared against the online interviews and Phase 2 site surveys to identify patterns in experience.

Phase 4, reported here, trialled in controlled conditions the interaction of fifteen volunteer participants against selected kerb types and upstand heights considered to be most representative of those found in standards.

This study is intended to enhance comprehension regarding the impact of kerb design and usage on mobility, providing substantial evidence for robust kerb design; a domain that has been comparatively underexplored. The study does not seek to change current standards or guidance around the provision or design of dropped kerbs or crossing points (controlled or uncontrolled).

The findings will contribute to evidence-backed standards development, not only in Scotland, but also in the broader UK and beyond relating to kerb upstands.

Methodology

In Phase 4 a laboratory experiment used an adjustable height platformed system with interchangeable kerbs. The experiment used controlled conditions and a safe environment to gather qualitative and quantitative information from volunteer participants with a range of impairment conditions across five study groups:

  • Low Vision capability group (e.g. Cane and Guide-dog),
  • Moderate Vision capability group (e.g. Retinal and Macular Degeneration),
  • Low Physical capability group (e.g. Wheelchair),
  • Moderate Physical capability group (e.g. Walking stick), and
  • Baseline (Normative) control group (no physical or vision related impairment).

Participants were asked to find and traverse four selected kerb profiles at different upstand heights between 20mm and 100mm (depending upon the kerb profile). They were asked to describe their thoughts before, during, and after the process. After traversing a kerb, they were asked to score the perceived workload (or effort required) of completing the movement using NASA Task Load Index (TLX) which is a subjective assessment tool widely used in Human Factors and Ergonomic research.

The objectives of the Phase 4 trial were to attempt to validate the previous phases of the study under controlled conditions and add robust quantitative data to the qualitative findings of previous phases. Further, Phase 4 sought to define a range of kerb upstand heights which would prove equal to all users, if possible.

To correlate the quantitative data with the qualitative information found in the previous phases additional qualitative data was also collected. Qualitative recordings of each participant’s experience as well as their responses to requests for commentary were taken and transcribed at key points during the contact between participants and the kerbs.

Findings

The principal findings from both the quantitative and qualitative data are:

  • Perceived workload ratings were predominantly a combination of physical and mental effort. The amount of mental effort reported increased with reported physical effort.
  • The 20mm - 25mm kerbs were detected and traversed easily by the Low and Moderate Physical capability participants. There was no preference for any of the kerb types with workload scores similar across all types.
  • The 20mm - 25mm kerbs were detectable by the Low and Moderate Vision capability group participants, but with more difficulty than higher upstands. Occasionally they were not noticed by guide dogs when the participant was stepping down off a kerb.
  • The 50mm – 60mm kerbs were not traversable by wheelchair users without the use of a third wheel attached to the chair or additional assistance.
  • The 50mm kerbs were detectable and preferred by Low and Moderate Vision participants. Although there was a preference for the Half-Batter and Bull-Nose vertical faces over the Full-Batter.
  • The 60mm kerbs were found by the Low Vision participants to require the lowest workload. However, combining workload scores from both Low Vision and Moderate Vision groups, the 50mm kerbs were preferred by visually impaired participants overall.
  • The 100mm kerbs were considered hard and frustrating by all user groups, even the baseline group.
  • The statistical findings were fully consistent with the pattern of results.

Conclusions

This report does not set recommendations for statutory bodies but presents information and conclusions which can be used by them to determine the future guidance.

It was concluded that these laboratory findings were consistent with the findings of the previous three phases of the project. The findings from the Phase 3 field work demonstrated a clear division between visually impaired users and physically impaired users in their response to kerbs.

Taking all groups into account it was calculated that the equitable kerb upstand height for both user groups was likely in the range between 40mm and 50mm for all kerb profiles.

Detailed conclusions for perceived workload showed some variability in workload based on kerb profile and the specific functional impairment but with overall trends remaining similar across kerb profiles.

There are several clear indicators towards possible further areas for research and evidence gathering, which could further inform standards and guidance.