Results analysis

Equal Workload Point

During the analysis of the quantitative TLX workload data, it was observed that the workload of the Vision groups would always cross the workload of the Physical group. For each kerb type this point would be somewhere between the 25mm and 50mm kerb upstand. Theoretically, this point would be the location where both the Vision and Physical groups have an equal level of perceived workload.

Following the method described in ‘Appendix A.1 Linear Interpolation of Results to mathematically interpret’ this point was calculated for each kerb type. It was found that a kerb upstand in the range of 40mm - 48mm could be of equal workload for both the Visual and Physical groups. Considering engineering standards this would translate to 40mm or 45mm upstands.

The equal workload at this point would be between 23 and 29 on the TLX workload scale depending on kerb profile. This equates to a Medium level of workload on the category scale used in this report.

Statistics

The TLX quantitative data was statistically analysed using the methods described in Appendix A.3.

When considering the Low Vision group, the test between Half-Batter 50mm and 25mm kerb heights shows there is statistically significance difference at a greater than 95% level of confidence.

There was found to be a lack of difference between the Low Vision and Moderate Vision group scores which is likely attributable to the overall similarity of scores between these two groups. These differences are too small to be detected at the test power and sensitivity.

For the Physical group, there is evidence of statistical significance of differences in Full-Batter 50mm and Half-Batter 25mm results with a confidence level greater than 99%. Similar outcomes were shown between other combinations.

The purpose of this exercise was to determine whether the differences between observed perceived workload ratings for different conditions (Kerb x height) were not due to chance, at a significance level of 5 in 100 (P<0.05).

Analysis of Visual and Physical Results

When considering the quantitative and qualitative results across all kerb profiles and upstand heights the following patterns were detected:

• 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 Cycle Segregation kerb, in particular, was hard to detect by the Low and Moderate Vision groups at 20mm or 25mm but they found the 50mm Cycle Segregation kerb height significantly easier reporting a reduction in the overall workload score.
• 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. 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 (Bull-Nose and Half-Batter) were considered hard to traverse and frustrating by all user groups, even the baseline group.
• Overall, the statistical tests produced results that were consistent with the Qualitative results and integrated analysis.