Introduction

General

This report documents the process and findings of the Inclusive Kerbs Phase 4 research project. The project was commissioned by Transport Scotland on behalf of the Scottish Roads Research Board (SRRB) and the Department for Transport (DfT) and was conducted by Mott MacDonald and Edinburgh Napier University’s Transport Research Institute. The Phase 4 research is part of the wider Inclusive Kerbs Research Study, made up of four phases of research of which this is the final phase.

The study may lead to the change of existing, or development of new, guidance for Scotland, the UK, and beyond; it has therefore been designed to be as robust and rigorous as possible within project constraints, and to stand up to scrutiny and challenge. To achieve this, the project has used best practice methods in the design and implementation of this research project.

To direct the research and establish a foundation of prior knowledge Phase 1 conducted a literature review. The review evaluated relevant published academic research, and appropriate design policies, guidance and standards. Informal literature, including internet blogs, were also considered. Some seventy-six separate documents were reviewed as part of the study. Phase 1 established that kerb height was an under researched area, with only two papers identified with a clear research base and that the was no clear reason for kerb heights specified in standards or guidance.

To better serve the end user of any proposed kerb guidance, the project has a strong focus on the personal experiences of roadside users with functional impairments. Utilising the analysed population data, the project recruited a small number of interview participants from the highest impairment severity category to assist in online pilot interviews (Phase 2). This initial feedback was used to assist in the method development for the online and site-based interviews (Phase 3) and laboratory study (Phase 4).

Phase 2 surveyed a range of existing kerbs in different locations, collecting data on a range of attributes of kerb properties and its setting. The data gathered was then used in the Phase 2 online interviews and allowed limited associations to be made between experiences of kerb interactions and kerb design. These associations were then further defined during the Phase 3 study to allow more definitive conclusions to be reached with regard to the issues faced by functionally impaired users in the street. Finally, to understand the effect of kerb heights in isolation, laboratory-based testing has been conducted in this Phase 4.

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 findings will contribute to evidence-backed standards development, not only in Scotland, but also in the broader UK and beyond. The potential applications extend to related domains like crossings, signage, road markings, and vehicle automation, making this research a valuable asset for advancements in multiple related topics.

Scope and Objectives

Phase 1 of the study comprised of a literature review and recommended that a second phase be conducted looking at the kerb boundaries between footways and carriageways, footways and cycle tracks, and cycle tracks and carriageways.

Phase 2 of the study examined the interfaces identified in Phase 1 and how users interacted with them. It gathered necessary data, from online interviews with functionally impaired volunteers using a trial methodology to form a basis for recommending future studies on inclusive road design. The interviews considered the whole setting and use of the kerb for navigation, both parallel along a street, and as a point of uncontrolled crossing.

Phase 3 of the study extended to the collection of data from people with a range of capabilities, including severe to moderate and mild impairments (Langdon and Thimbleby, 2010). This was done through site-based interviews with functionally impaired volunteer participants using three of the sites identified as most appropriate from Phase 2 of the study. Data was gathered using on-site, concurrent verbal protocols, and interviews. It was compared and analysed using conventional qualitative research techniques (Neville Stanton, 2021) (J Goodman-Deane, 2010) (Flick, 2018) to identify key themes and patterns arising from the participants’ experiences. This data was then analysed in order to form conclusions on existing contextual kerb conditions and the relative difficulties encountered. The conclusions were used to form a realistic baseline and provide further clarifications on the design and methodology for experimental laboratory research in Phase 4 to identify potentially suitable kerb height ranges.

The aim of the Phase 4 research is to establish quantified evidence for the difficulties posed by the kerb and, if possible, define a range of kerb upstand heights which would prove equal to all users. The Phase 4 research sought to validate the previous phases of the study under controlled conditions which allow determined parameters (e.g. height, kerb profile) to be varied. Therefore, tests were conducted on kerb interactions within laboratory conditions.

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

Methodology

The laboratory trials were conducted at Edinburgh Napier Universality laboratories in a bright, clean, calm, warm, and dry environment. In so far as reasonably practicable the research team attempted to hold all other test variables constant.

The study involved the construction of a modular, variable height, articulated platform (the rig) located within the controlled indoor facility, that allowed participants to carry out the protocols securely. The rig consisted of a pair of modular platforms on jacks which could be raised or lowered independently of each other. The selected kerb was held securely in a cradle at the centre of the rig. The surface of each platform was covered in an asphaltic material to approximately match the colour of footways. The rig was accessed by a ramp and a surrounding wooden railing prevented falls from the sides. Section 2.5 further describes the set-up of the laboratory equipment including an image for reference.

The trials focused on understanding the workload or effort imposed by each kerb design, which might render the action difficult, frightening, painful, or even impossible for individuals. The NASA TLX workload questionnaire was used to gauge the perceived workload or effort required to detect and cross the kerb. This is a paper questionnaire widely used in Human Factors and Ergonomic research. It has been validated and tested for reliability in countless experiments worldwide since 1986 (Hart, 1988; Grier, 2015; Hart, 2006). Section 2.4 further describes the questionnaire in detail and how it was used.

Participants were interviewed about their lived experience of their interaction with kerbs and then invited onto the rig. On the rig they were asked to find and then cross the trial kerb, both up and down, while describing the experience to a member of the research team to record. They then left the rig and were asked to give numerical scores against each NASA TLX subscale. Meanwhile the experiment was changed onto another setting. Participants experienced kerb profiles in a different order to each other over several sessions. Cameras were held by the research team and attached to the rig to record the activity of the participants.

The project assessed four kerb profile types and five different heights. To fit within project constraints not all variations were assessed, with some not viable. In total fourteen different kerb heights and profile combinations were assessed.

The laboratory trials described in this report are the final part of the methodology of the holistic four Phase study. They are intended to validate and inform the self-reported findings from the previous interviews and site trials by use of tests in controlled conditions.

The project methodology is explained in greater detail throughout the report with specific focus in Section 2 - Methodology.

Report Structure

This report is structured to first provide the reader with the methodology used during this phase of the study as well as the background of how this method was developed and the intended outcomes. Followed by the details of, and the data gathered from, the laboratory interviews and TLX workload scores, along with the analysis of that data. The report then collates the findings from the previous phases and discusses them in context. Finally, the report provides outline conclusions, recommendations for further work and closing remarks.

The following sections of this report are:

• Section 2 which summarises the methodology used during the Phase 4 research.
• Section 3 which provides both the quantitative and qualitative results. The quantitative results from the TLX workload scores, along with the analysis of that data, are broken down by kerb type and height. The qualitative results are also presented by each kerb profile individually, with photos of participants and quotes from their commentary.
• Section 4 which describes the analysis of the results and how they can be interpreted.
• Section 5 which discusses the results in conjunction with the key findings from the previous phases of this research project. The qualitative data from their Phase 4 comments and TLX workload quantitative data are compared against the findings from previous phases to identify any patterns in experience and inform a range of kerb heights that would be most suitable for the varying impairment types.
• Section 6 which provides a summary of the outcomes and conclusions from this phase of the study along with recommendations for further study.