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Mind the gap!

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Britain’s rail and tube passengers get on and off trains around six billion times each year, generally without incident. However, just occasionally, crossing the platform train interface (PTI) can go wrong. Over the last five years, PTI accidents on the mainline network have resulted in, on average, 1,354 minor injuries, 51.6 major injuries and 3.0 fatalities per year. The figures for London Underground, which has 43 per cent of UK rail journeys, are respectively 409, 14.4 and 1.2.

PTI accounts for 48 per cent of the UK passenger fatality risk on the mainline network. Generally, such fatalities involve moving trains, whereas minor injuries occur when boarding and alighting from stationary trains.

The Institution of Mechanical Engineers (IMechE) held a seminar recently to raise awareness of PTI risks and their solutions. This was well-attended, with representation from all aspects of the industry, and included presentations from Network Rail, RSSB, RAIB, Crossrail, Thameslink, Heathrow Express and PAMELA (see below).

The key issues at this seminar were perhaps best summed up in two often used phrases: “We are running twenty-first century trains on nineteenth century infrastructure” and “Passengers think train doors are the same as lift doors”.


The UK mainline network has just over 2,500 stations with 6,000 platforms. RSSB’s principal infrastructure engineer Bridget Eickhoff showed just how variable these platforms are. For new platforms, Group Standard GI/RT7016 specifies a height of 915 mm and offset of 730 mm, within defined tolerances, for new station platforms.

This standard also specifies that new stations shall not be located on curves of less than 1,000 metres. This avoids an excessive gap at centre vehicle doors. On a mixed traffic railway that includes freight, these dimensions are a trade-off between gauging requirements and passenger requirements.

As an illustration of the issues associated with historic rail infrastructure, of all platforms on the network, the height and offset requirements are achieved for 30 per cent and 22 per cent respectively, with only seven per cent complying with both requirements. A fifth of all platforms fail to meet the curvature requirement.

This is a problem for which innovative solutions are required, as rebuilding thousands of legacy platforms to comply with standards for new stations is not a realistic proposal. Bridget felt that, for certain routes, the idea of a go-anywhere train might not be a good idea. Merseyrail shares this thought as their new train fleet, to be delivered in the early 2020s, will be tailored to its network.

Lights, Gaps and humps

On new lines, a fresh approach can be taken. In its central tunnel sections, Crossrail will have a platform height of 1100 mm with level access over a narrow gap. Heathrow Express (HEx) also has this apparently ideal arrangement although at Paddington the platform curve results in a large gap at the front of the train. Its operations director, Keith Harding, explained that, to address this hazard, blue flashing lights have been installed under the platform edge which light up when the train is by the platform.

Gap filler fitted to Heathrow Express platforms.

Keith further stated that, with 65 accidents over a three-year period, this narrow level gap has not been problem-free as passengers do not perceive it as a hazard. In 2015, gap fillers were installed to prevent such accidents. These are hard-wearing rubber strips mounted on the platform edge and were first successfully trialled at the airport’s Terminal 5 station. During the year-long trial there were no step board accidents. The gap fillers were supplied by Delkor Rail and HEx is their first application in the UK.

Crossrail’s rolling stock and depot manager, Phil Hinde, explained that, in addition to 1100mm-high level-access platforms, Crossrail’s central section will also have platform edge doors (PED). As these doors are critical to station operations, prospective suppliers were asked to specify door cycle times in milliseconds. Phil noted that there are no standards for PEDs which, amongst other things, present an entrapment hazard and need robust earthing given their proximity to 25kV AC overhead lines.

Outside the central section, Crossrail trains will not have level access. Phil explains that platforms on its routes out of Liverpool Street are generally higher than the 915mm standard, whilst those out of Paddington are generally lower. Some work is being done to resolve these issues.

To provide easy wheelchair access on Thameslink, its safety systems manager, Fraser Scott, described how some stations are to have their platform height raised using a modular hump system which uses glass-reinforced polymer sections and is supplied by Pipex Structural Composites. This was first installed in 2008 at Harrington on the Cumbrian coast at a cost of £25,000, about a tenth of that would have been otherwise required to make the platform comply with the disability access regulations.


Taku Fujiyama and Sebastian Seriani of University College, London gave an interesting presentation on the University’s Pedestrian Accessibility Movement Environmental LAboratory (PAMELA). This was completed in 2006 to provide a full-scale simulation of pedestrian infrastructure. A visit to this facility was an optional part of the seminar package.

Taku explained that PAMELA can vary factors such as height, stepping distance and door widths to optimise asset design for passenger movement behaviour. Without such a simulation, designs are likely to be sub-optimal as it is not possible to isolate the effects of these variables. In 2008, the laboratory was used to assess boarding and alighting performance of the proposed Thameslink trains – 150 participants were recruited and over 11,000 passenger movements recorded.

PAMELA has also been used to assess optimum train/platform configurations on London Underground and the effect of various types of platform markings at the door position. On platforms where humps have been provided for wheelchair level access, it was determined that the optimum ramp angle was 6.9 per cent. Another study concluded that, if step-free access could be provided for all Victoria line platforms, a return Walthamstow to Brixton trip would be reduced by two minutes.

The effects of PEDs on boarding behaviour have also been studied. With PEDs, more passengers wait at close to the platform edge in crowded conditions. In one simulation, it was found that, when more than 25 board and alight at each door, the provision of PEDs reduces the boarding and alighting time from 31 to 29 seconds.

Train design

In his presentation, Simon French, chief investigator for the Rail Accident Investigation Branch (RAIB), noted the need for improved train design. He thought that improved obstacle detection technologies such as proximity detection systems and enhanced sensitive door edges could do much to reduce the fatality risk.

RAIB reports had shown that other train design features needed to be addressed to reduce PTI risk. Simon mentioned how, on some trains, passengers can open doors after the driver has initiated the door close sequence. Thus, doors close immediately after opening with a consequent increase in the risk of passengers being trapped in the doors.

He also stressed the need to minimise the force needed to extract objects caught in closed doors and to ensure the reliable operation of sensitive door detection systems.

Human factors

Although improved engineering controls can do much to reduce PTI accidents, perhaps the most important and difficult issue is human behaviour. Passengers may not understand the danger caused by their action. Staff may not fully understand PTI risks and, like all human beings, can make mistakes.

In his presentation, Allan Spence, chair of the industry’s PTI strategy group, explained how train despatch arrangements were heavily dependent on a single human doing a very repetitive role when interventions are very rarely required. Such circumstances are likely to result in ‘look but don’t see’ accidents.

He felt there was a need to review station despatch arrangements. For example, platform dispatchers are required to observe trains on departure. However, there is nothing they can do if they see something amiss once they have given the train ready to depart indication.

Train boarding simulation at PAMELA.

Simon French felt there was a requirement to more effectively engage with the public on the dangers of PTI incidents. Many passengers think that train doors operate like lifts and so deliberately put their arm in a closing train door. In one accident, a passenger did just this and made no attempt to withdraw her trapped hand whilst the train was stationary as she expected the door to open. It was only when the train moved that she understood the danger she was in. She was then dragged along the platform for 19 metres, but fortunately escaped without serious injury.

The accident also highlighted the need for better staff training on PTI incidents. In this incident, the driver had received a door interlock light to confirm the doors were locked and closed. RAIB’s investigation identified that he, and other railway staff, wrongly believed that this light would not illuminate if someone was trapped in a door.

Dwell time

PTI is both an operational and a safety issue. Crossrail’s Phil Hinde considered that a “metro mindset” is essential for the running of 24 to 30 trains an hour through its central tunnels. To help achieve this, passengers will be given information on which parts of trains are busy, trains will have dwell time counters and interior layouts matched to stations which have entrances at both platform ends. In addition, Crossrail’s concession contract will specify improved station staffing.

Thameslink is also focusing on station staffing when the number of trains through its centre section increases from 16 to 24 in 2018. Fraser Scott advised that the company has worked with French transport group Keolis and SNCF to understand how passenger behaviour is managed at busy French stations.

Fraser also mentioned the concept of nudge theory, which uses indirect suggestions to change behaviour. He illustrated this concept with an example of the etched image of a fly in the urinals at Schiphol airport which has reduced spillage by 80 per cent (readers can work out how this works for themselves). A further example is yellow shark’s teeth marking on the door rubbers.

A presentation by Michael Adlington of the Rail Delivery Group focused on the needs of passengers in wheelchairs who make 400,000 journeys each year. He noted that, of the 2,500 UK mainline stations, only 450 had step free access and that there are 25 types of wheelchair ramp in use. Wheelchair users have reported that they do not feel safe using these ramps, which have been a factor in the 192 PTI accidents last year that involved wheelchair users.

Thinking out of the box

The IMechE is to be congratulated for arranging its informative PTI seminar, which clearly presented the complexity of this issue, work done to address PTI challenges and the actions required to further reduce this risk. Much of this is contained in the RSSB’s platform train interface strategy, produced by the cross-industry PTI strategy group in 2015. However, there is no substitute to hearing practitioners describe the issues.

In September, RSSB also launched an app to assess the sufficiency of station PTI risk controls. It is also intended to give station managers a better understanding of PTI problems. The data captured by this app is held on a single database to provide an overview of PTI risks. RSK Business Solutions produced this app to a specification developed by RSSB research project T1029.

The high-profile dispute about whether the driver or guard operates the train doors was not mentioned at this event. This is perhaps not surprising as the seminar showed that PTI safety requires a mix of train and infrastructure engineering controls, effective operational management and the management of human factors. PTI safety is about much more than who controls the train doors.

As Keith Harding advised the seminar, it also requires “thinking out of the box”. Heathrow Express has recently engaged 22 students from London’s University of Arts to address the PTI risk without any pre-conceptions. Keith commented that these students have shown massive creativity and “will soon reveal great things”. We await this development with interest.

Written by David Shirres


  1. Well I’ve seen someone disappear down the gap at platform 17 at Clapham Junction, on the ridiculously curved platform there (they were okay), it is a major problem. Indeed it’s a bigger issue when the levels are the same – there’s clearly something about a step that helps.

  2. I recently travelled from Chesterfield to Birmingham. The gap on Paltform 10/11 was so big I nearly could not get off or on for the retuen journey,When are they going to do something with gaps on these platforms which are the worst ones of all? we nned a ramp or raising of the platform level

  3. You would think all platform heights would be a Universal height and all train doors would be the same height so as to facilitate a level access to and from the train. Whereas this seems to be the case on Underground systems it is sadly not the case for British main line services. It’s all a bit hit and miss as to gaps and heights dependant on the station you are at, I have never found a level access at a main line station and at some you need to be quite athletic to get on and off the train. 2 places in mind, Bridgwater and Hampton Court.


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