Methodology
Introduction
This phase built upon and continued the research from the previous phases which were conducted using online interviews and on street trials. In this phase a laboratory experiment in safe controlled conditions at Edinburgh Napier University was conducted using an adjustable height platform system with interchangeable kerbs to gather qualitative and quantitative information from volunteer participants with a range of impairment conditions.
Participants with different levels of visual and/or physical impairment were asked to find and traverse four selected kerb upstand heights between 20mm and 100mm (depending upon the kerb). They were asked to describe their thoughts before, during, and after the process. After they had traversed a kerb, they were asked to score the perceived workload using the NASA Task Load Index (TLX) assessment tool.
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.
Participants
An ambition of the Inclusive Kerbs Study was to represent the proportions of the Scottish population who reported difficulties in daily life at various levels of severity in the functional areas represented in the Family Resources Survey (2019-2020) as outlined in the Phase 2 report.
The Scottish population data taken from the Family Resources Survey (2019-2020), discussed in Phases 2 and 3 of the study, showed that nearly 50% of those who responded to the survey had some level of functional impairment such as, difficulty with vision, stamina, learning and memory, hearing, mental health, social and behavioural capabilities, mobility, and dexterity. The results for each functional impairment were also sub-categorised by age and gender.
However, identifying and arranging participation of the range of volunteers required to meet the exact percentages of each functional impairment which represent the population would significantly expand the scope of the study beyond the project constraints. It would also detract focus away from those who are predominantly affected by the issue of kerb upstand heights and profiles.
In Phases 2 and 3, the research team concluded that the two main categories of functional impairment which affected how people interacted with kerb heights and profiles were; mobility and dexterity (physical capability), and difficulty with vision. In the Scottish population data, 45% of those who reported a functional impairment reported difficulty with mobility and dexterity, and 10% reported difficulty with vision.
The Phase 4 research therefore focused on these two principal categories; mobility and dexterity (physical capability) and vision. Age and gender were not controlled and were recruited opportunistically based on availability of volunteers. The volunteer participants for Phase 4 were accepted into one of five participant groups based upon their dominant functional impairment:
- 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).
The opportunity to participate was advertised by an information release and ‘call for participation’ distributed to relevant Scottish organisations by email. Several previous participants from prior phases who had indicated their willingness to continue were also contacted.
The following list of organisations were contacted and assisted in finding volunteers for the study:
- Spinal Injuries Scotland
- Scottish Guide Dogs for the Blind
- Roads for All forum
- The Royal National Institute of Blind People (RNIB)
- The Scottish RNIB
- The Pocklington Trust
- Disability and Equality Scotland
- Lothian Council
- The Mobility and Access Committee for Scotland
- The Edinburgh Access Panel
- Health and Social Care Alliance Scotland (the ALLIANCE)
- Centre For Inclusive Living Perth & Kinross
Along with a description of what to expect and what level of commitment was required volunteers were sent an information pack with details of the purpose, funding, and stakeholders on the project. It was explained that informed consent would be required, their data management rights were explained, and that participants were informed that they could withdraw at any time and the safety and comfort provisions were outlined. A small honorarium retail voucher was offered to participants as an acknowledgement of their effort and any travel expenses were reimbursed as appropriate.
Group | Participants | % |
---|---|---|
Low Vision | 3 | 20% |
Moderate Vision | 5 | 33% |
Low Physical | 2 | 13% |
Moderate Physical | 3 | 20% |
Baseline control | 2 | 13% |
Total | 15 | 100% |
Kerbs
Four kerb profiles were identified for assessment from the Phase 2 and Phase 3 studies. These are common kerb profiles used in engineering and streetscaping projects. These were:
- Full-Batter – kerb with a 45-degree splay
- Half-Batter – kerb with a 12.5-degree splay
- Bull-Nose – kerb with a straight 90-degree edge
- Cycle Segregation – large kerb with a 45-degree splay on one side and 12.5-degree on the other.
Previous phases of the research study indicated the different heights these profiles of kerbs were likely to be found at, and which heights and profiles caused problems for the functionally impaired community.
Within the project constraints, 14 kerb upstand heights and profile combinations were chosen from the upstands and profiles identified.
The Half-Batter and Bull-Nose were tested at upstands of 25mm, 50mm, 60mm and 100mm. To avoid unnecessary repetitive testing the Full-Batter was not tested at 100mm, as it was already found to be difficult for all participant groups when testing the other kerb profiles.
The Cycle Segregation kerb was tested at upstands of 20mm, 25mm and 50mm. The shape of this kerb does not allow higher upstands.
The kerb elements conformed to BS EN 1340:2003 Concrete Kerb Units.
A matrix of the profiles and upstands used in the Phase 4 experiment can be found in Table 2‑2, below.
Kerb Profile upstand | 20mm | 25mm | 50mm | 60mm | 100mm |
---|---|---|---|---|---|
Full-Batter (SP) | No information | FB-25 | FB-50 | FB-60 | No information |
Half-Batter (HB2) | No information | HB-25 | HB-50 | HB-60 | HB-100 |
Bull-Nose (BN) | No information | BN-25 | BN-50 | BN-60 | BN-100 |
Cycle Segregation (CS) | CS-20 | CS-25 | CS-50 | No information | No information |
NASA TLX
The NASA Task Load Index (Hart, 1988) is a multi-dimensional psychological rating procedure that provides an overall workload score based on a weighted average of ratings on six sub-scales: Mental Demands, Physical Demands, Temporal Demands, Own Performance, Effort, and Frustration.
The NASA Task Load Index is a two-part evaluation procedure consisting of both weights and ratings. The first requirement is for each participant to evaluate the “weight” of each factor to the workload of a specific task. This sets how much the participant felt that factor contributed to the task. The weighting is obtained for each different task or task element upon its completion.
The second requirement is to obtain numerical ratings for each factor on a scale of 0 to 100 that reflect the magnitude of that factor in a given task. Participants responses were recorded by marking each scale at the desired location. A weighted workload score is thereby calculated using the source of workloads and the rating sheets for each task.
For this experiment the numerical scores were then interpreted based on the calculated workloads and categorised as:
- Low (0-9),
- Medium (10-29),
- Intermediate (30-49),
- High (50-79), or
- Very High (80-100).
Based on the results of the weighting procedure, the TLX direct unweighted ratings can be used directly. This method is predominantly used in contemporary human factors studies (Grier, 2015; Hart 2006). The significance of the sub-scales is dependent on the nature of the task and if the unweighted scores are highly correlated, they may be used interchangeably with weighted scores. Therefore, for the purposes of this research we have used the unweighted scores. All references to the workload scores in the following sections of this report are the unweighted workload scores.
Test Platform
The study required the construction of a system which would allow participants to experience different kerb upstands and profiles safely.
The test platform, ‘the rig’, consisted of two platform units abutted to each other with the ability to vary heights independently. In the centre a cradle securely held the selected kerb.
The modular nature of the rig allowed for it to be reconstructed between sessions. Maximising space saving while maintaining the capability for multiple kerb element changes.
Access to the platforms was provided by a ramp sufficient for a wheelchair user with a less than 1:12 slope.
The unit sections were surfaced with a hard-wearing and rough, bonded grit, unreflective material in order to approximate an asphalt surface. The ramp platform dimensions were based on Building Regulations Part M to allow a wheelchair to have sufficient manoeuvrability with additional space for the experiment safety personnel to occupy the platform as well.
To create a safe environment the laboratory was cleared of hazards before each participant began each experiment. Each platform was protected with a robust wooden railing to reduce the likelihood of falls off the sides. On the platform with each participant a designated safety person was positioned to step in and provide assistance if required.
During the experimental procedure the central channel located between the two platforms allowed the positioning of standard kerb units. These were lowered into position using a gantry crane after the sections were locked together. The height differences required by the experiment were attained by adjusting the heights of the jack pads. Kerbs were fixed into the channel using a sand filler to reduce movement.
Experimental Procedure
Participants were guided to the laboratory safe area and provided with a safety briefing by technicians. The researcher then explained what was to happen and how the experimental rig was configured. Participants were read the relevant consent information, including the right to stop at any time. The type and upstand height of the kerbs were not disclosed to the participants, and the order of the kerb types was non-sequential.
There were two researchers present at all times. The first interacted with the participant and monitored them throughout the experiment. They carried a GoPro camera on a head mount to record the details of the participants traversing the kerbs and their statements in response to predefined questions. The second researcher had a safety role and was required to be near the participant at all times to provide assistance if necessary and mitigate against safety risks such as slips, trips, falls, or collisions. They were also required to ensure the participant made safe progress up and down the ramp. A second camera was mounted to an adjacent gantry and recorded all movement on and around the rig.
Each participant was escorted onto the rig using the ramp. They were rotated 90° to face the kerb and asked to cross it (going down the kerb). Their actions and comments were observed and recorded. Once across they were asked to rotate 180° to face the direction they had navigated and to cross back over the kerb (going up the kerb), thus experiencing both up and down perpendicular kerb traverses. They were also asked if they could find and track the kerb laterally, if possible. Finally, they were asked how they felt making the crossing, in both directions. This forming the basis of the qualitative notes.
After leaving the rig via the ramp they were escorted to a comfortable seating area and the researcher orally went through the NASA-TLX questionnaire, recording their responses on the paper. Participants then waited for their next kerb upstand height and profile to be set or returned on another occasion. Refreshment and lunch were supplied in a comfort room in a separate part of the building.
The procedure was based around an experimental design with two variable factors of the kerb height and kerb profile. The participants experienced all conditions, and the order of presentation of profiles and upstands was randomised.