Investigation into Platform Hump Options

0. Executive summary 0-1. Aim of the research London Underground Limited (LUL), as part of its endeavour to improve accessibility on the LUL network, has decided to consider the installation of short humps at its stations. The main aim of this research was to provide evidence which will enable LUL to develop standards for the design of humps on station platforms. The objectives of this research were • To find out the acceptable extent of design factors of humps, such as the ramp gradient, in terms of comfort and safe usage. • To make suggestions regarding the design of platform humps. 0-2. Method Humps consist of several design factors, such as the slope gradient and the length of the level part. At first, the factors to be considered in design standards for the installation of humps were identified. Then, four experiments were conducted to investigate how a change of each design factor affects behaviour of participants with restricted mobility. In each experiment, we changed the degree of each factor, and observed how the mobility performance of the participants changed. We also asked about the participants’ subjective evaluations on the tested humps. In total, 63 participants attended experiments. The participants were ranged across a number of categories, relating to their mobility characteristics and included wheelchair users and visually impaired people as well as those with other mobility restrictions. 0-3. Summary The acceptable extent of each design factor was concluded as below. a) Lighting level We did not find any significant difference between the results in the dark and bright conditions tested. This factor may require further investigation. Comments from the participants suggest that even lighting levels are important for visually impaired passengers, and thus increasing lighting level only for the hump (but not the whole platform) should be avoided. b) Slope gradient Some participants felt unsafe with the slope gradient of 6.9% (1 in 14), although there is no significant difference in physical performance. We concluded that ramps with any of the gradients tested would be acceptable if there is no other option available. However, where possible, the gradient should be lower than 6.9%. c) Gap difference and sill to platform Gap difference should be as small as possible. It was found that an increase of the difference immediately leads to low performance and a perception of being unsafe. It should be noted that no wheelchair participant could go over gaps when the horizontal difference was more than 75mm and the vertical difference was more than 50mm. d) Stepping out It was found that, when participants stepped out onto a slope, the vertical and horizontal difference between the door and the platform was a major issue for performance and perception of safety, and the slope gradient was not. However, the result of the analysis on people with a mobility restriction and people with visual impairment, who failed to step out, showed that a steep slope would give some additional difficulty in stepping out. If a door is expected to stop at a ramp, a gradual gradient (3.0%; 1 in 33) would be recommended for this ramp. e) Length of upper level part In the experiment, it was observed some participants needed a 2.0m to 3.0m length in order to manoeuvre onto a train. This length is more than the width of one door. We recommend that the length be sufficient to cover at least the two main doors of a carriage, so that for all train types serving that station there is always at least one door stopping at the level part even if the train were not to stop at the normal position. f) Backfall gradient Any backfall gradient can be used as long as it is in the range tested in this experiment (1.5% to 2.5%; 1 in 66 to 1 in 40), as we did not find any difference in performance. g) Visual contrast Colour contrast should be used for humps. The participants prefer a different colour to be placed on the upper level part of the hump, as well as edges of the ramp. Free comments by the participants suggest that having different colours on the hump would not be enough to inform visually impaired passengers, and therefore we recommend that a proper signage system be introduced. h) Passengers and type of footwear The results suggested all the types of participants showed a similar trend. Participants with high heels felt less safe about gaps when the horizontal difference was more than 75mm and the vertical difference was more than 50mm. I) Requirement forRequirement of a handrail If a handrail cannot be installed, it would be possible not to have it on the hump. j) Hump width The hump width should be at least 2.0m and preferably more than 2.5m. 0-4. Conclusion and recommendation The results showed that a big vertical or/and horizontal gap is a big barrier for those with mobility restrictions, and the platform hump may be an effective way to eliminate the barrier. There are some design factors that have a threshold that needs to be addressed, such as 2.5m for the hump width. However, these are only design details and would not be in conflict with the installation of humps itself. An important conclusion is that any of the humps considered in these experiments would clearly be preferred to the combination of step and gap between train and platform. When designing humps, consideration should be given to the slope gradient and the size of humps as well as placing appropriate colour contrasts to humps. The results of the experiments suggest that these factors may influence safety and comfort of passengers with mobility restrictions. In addition to design details, it is always important for underground staff to give consideration to passengers with mobility restriction. Even though the train becomes accessible from the platform by means of the hump, our experiments suggest that some passengers with mobility restriction may need to make some effort and spend some time to cross even a small gap left in-between the train and the platform. A CCTV camera that covers the hump area and is linked to the driver’s CCTV array as well as to the CCTV control room would also help to ensure that underground staff including the driver can consider such passengers, be aware of any problems and take any necessary action. As this investigation did not consider the “crowd” issue, a further investigation would be needed to explore effects of crowds on those with mobility restrictions and vice versa and any impacts on dwell times in the stations. In addition, a comprehensive investigation into a coherent sign/guidance/lighting system would be necessary, especially in relation to platforms at surface stations.