Methods: As Per Experiment 1 and 2 Unless Otherwise Stated

Experiment 3: 15 older participants (6 female; age 69.9 ± 7.3 years; height 1.70 ± 0.11 m; mass 77.75 ± 18.75 kg) with habitual visual correction descended a surface level change walkway (henceforth referred to as walkway), the height of which was varied (165 mm and 195 mm). Trials were repeated 3 times.

The walkways were 1000 mm wide with a walking surface area measuring 2000 mm long (figure S1). The two different walkways heights represented surface level changes typically encountered during activities of daily living such as stepping down from a kerb or alighting from public transport. Both walkways were painted a uniform grey colour. Crash mats were positioned on the right and left sides of the walkways for safety.

Methods: as per experiment 1 and 2 unless otherwise stated.

Results: Mean and SD data of foot placement and clearance parameters are shown in Table S1. Highlighter condition had a significant effect on final foot placement (p < 0.001); placement was further from the tread edge for away10 in comparison to plain (p = 0.002), and for away30 in comparison to abutting (p = 0.025) or plain (p < 0.001). Highlighter condition had a significant effect on heel placement (p = 0.003); placement was closer to the tread edge in the away30 condition compared to abutting (p = 0.016) or plain (p = 0.015).

Highlighter condition had a significant effect on horizontal and vertical FC (p < 0.001 and p < 0.001 respectively). Horizontal FC and vertical FC for away30 were significantly closer to the tread edge than plain (p < 0.001 and p < 0.001 respectively), abutting (p < 0.001 and p < 0.001 respectively) or away10 (p < 0.001 and p < 0.001 respectively).

Highlighter condition had a significant main effect on descent duration (p = 0.035), but post-hoc analysis indicated there were no significant differences between highlighter conditions.

There were no significant differences in within-subject variability between highlighter conditions in any of the outcome parameters analysed (penultimate and final foot placement, horizontal or vertical FC, heel placement or descent duration).

The percentage of the total number of trials that resulted in a heel scuff or where horizontal FC fell below 5 mm was minimal (2%, Table S2).

A discussion of the results is incorporated within main part of manuscript.

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