Boarding or alighting from a train can still be difficult on much of the Great Britain (GB) mainline railway, even where accessibility has improved in other areas. The issue lies at the platform–train interface (PTI): the step and gap between the platform edge and the train door or footstep.
On Britain’s mixed-traffic railway, that interface is shaped by the historic network non-standard platform heights and offsets, freight train clearance needs, and high floor fleets that stay in service for decades. That means there is no single fix. Lower-floor trains can help, especially when paired with sliding steps or bridge plates, but they cannot solve every problem on their own. Platform geometry still matters, as do operations, stopping accuracy, and the needs of different passenger groups. Improvement will come from treating the PTI as a system, not as a problem for either trains or stations alone.
Problem in context
It is easy to talk about accessibility as if it were simply a matter of removing a step or reducing a gap. In reality, the PTI on the GB mainline is much more complicated. Britain’s railway grew over a long period and was built by many different companies, often to different local standards. As a result, platforms vary a great deal in height, distance from the track, curvature, and surrounding clearances. Some are straight and generous; others are curved, narrow, or constrained by bridges, buildings, or track layout. Indeed, track improvements over the years have sometimes made matters worse.
Those variations make it very hard to design one perfect solution. It also explains why improving the PTI across the network is such a large task. With around 2,500 stations and roughly 6,000 platforms on the mainline railway, even small improvements add up to a major long-term programme.
For new and renewed platforms, the GB target is a height of 915mm above rail level and an offset of 730mm from the nearest rail. They reflect a compromise between better boarding for passengers and the need to keep enough clearance for trains, especially on routes that also carry freight. If a platform is higher, the step up into the train is often smaller, but the horizontal gap would need to be larger. That trade-off is at the heart of the PTI problem.
A key difficulty is that much of the existing network does not match the target geometry. Only a relatively small number of platforms are close to the target in both height and offset. Moreover, train step heights and widths vary between fleets. So, while the standards are helpful, the trains running today still have to work with a large and inconsistent legacy estate, and low floor trains of the future are not the whole fix.
No ‘one size fits all’
Another important point is that there is no single ‘accessible passenger’. Different people experience the same step and gap in very different ways, even if ‘level access’ is provided. Users of wheelchairs with small front wheels may be especially affected by a horizontal gap that looks modest on paper. Someone with poor balance may find the vertical step more difficult. Some people can cope with steps but rely on suitable handrails. Older passengers, people using walking aids, parents with buggies, travellers with luggage, and passengers with sensory impairments may all face different barriers at the same doorway. The real question is not simply whether a PTI is accessible in theory: it is whether a particular platform and train pairing is workable, safe, and reasonably independent for the people who actually use it. This can be a complicated issue when a variety of different trains use the same platform.
That thinking sits behind the boarding-category approach being developed in RSSB research project T1398. Instead of asking only whether a platform or train is compliant, the work looks at what passengers can really do. Can most people board independently? Do some need help? Are some interfaces unsafe even with assistance?
This is a useful shift because it links physical geometry to practical outcomes such as independence, continuing need for staff support, dwell time, and service reliability. It also helps the industry decide where to act first. On a network as large and varied as Britain’s, not every platform can be rebuilt quickly, so the ability to prioritise the places where improvement will make the biggest difference is essential.
Rolling stock as part of the solution
From the early days of railways, passengers stepped up into trains which had the floor installed on an underframe above the wheels. As the railway developed, engineers used the space underneath for equipment, bogies, and associated systems. Newer lower-floor designs offer a better fit with a wider range of existing platforms but often have to make compromises to achieve this such as equipment in what would normally be passenger space and narrower floors. The narrower floors reduce standing area at doorways and can constrain foot space at window seats. The logic is simple though: if the train floor is closer to platform height, boarding becomes easier, and devices such as sliding steps deal with the gap more effectively.
Greater Anglia (GA) and MerseyTravel were early pioneers showing what could be done, Greater Anglia’s Classes 745 and 755 trains use lower floors together with train-based sliding steps to reduce the gap to the platform. Merseyrail has gone further. As well as providing low floor Class 777 trains with sliding-step technology, it has modified many of the platforms on its defined network to the GB standard position to match the new trains more closely. Both cases show that better boarding is possible within GB conditions. At the same time, they also show the limits of relying on trains alone. Solutions work best where the infrastructure is consistent. On the wider GB mainline, where platform conditions vary so much, it is harder to guarantee the same result everywhere.
As mentioned, lower floors also come with technical trade-offs. If the floor is lower, there is less room underneath the train for equipment. That is often manageable on electric multiple units, but it can be more difficult on self-powered vehicles.
If a flat floor is desired through the length of a train, then lower floors may also need smaller wheels. This can work well for typical suburban trains (with doors at one third and two thirds along the body) at many mainline speeds, and may be possible for Inter-City trains up to 200km/h. However, it becomes more challenging at higher speeds because of wheel rotation and bearing limits.
Self-powered trains might be challenging too, so low floors are not a universal answer. They are a design choice with real accessibility benefits, but those benefits must be balanced against route requirements, propulsion layout, maintenance, and long-term performance.
Implications for infrastructure
As stated above, some platforms are simply too low, too high, too curved, or too constrained to offer good boarding consistently, whatever train arrives. That means some physical change to platforms will still be needed. The problem is that such works are rarely straightforward. Under-track structures, bridges, overhead line equipment, drainage, station buildings, curves, switches and crossings, lifts, and other fixed features can all limit what can be changed and how much it will cost.
That is why the most realistic approach is selective rather than universal. Raising very low platforms can bring immediate benefit for many trains and passengers by reducing the worst vertical steps. In some cases, overly high platforms may need to be lowered or re-profiled to support a more consistent long-term strategy, even if that creates short-term trade-offs. There may also be places where local raised sections are useful (such as are used on some Central London Thameslink stations), but those tend to work only where door positions are fixed, rolling stock is consistent, and freight is not a constraint.
The aim cannot be to make every platform identical overnight, but to focus effort where physical intervention will improve boarding for the widest range of passengers – and especially targeted if low floor trains are planned for the route.
Operations, risk, and limits
Operations also matter. At the majority of stations, the railway relies on staff-deployed ramps for assisted boarding/alighting. But this is not the same as independent boarding. Using ramps takes time, creates handling risks for staff, and may not be practical at narrower platforms or busy locations where dispatch is already difficult. Assistance has an essential role in today’s railway and is likely to be even more important in the future with an ageing population, but it should be seen as a mitigation within an imperfect system, not as the ideal end state.
For many people, the horizontal gap may present the greater risk, especially for wheelchairs, buggies, and passengers whose foot placement is uncertain. A step can often be seen and managed if it is within reason; a wide gap is less forgiving. This is one reason why sliding steps are so valuable. They cannot solve every problem because they do not remove all vertical mismatch, but they can reduce one of the most serious and least tolerable parts of the PTI. When combined with clear threshold marking, good lighting, and accurate stopping, they become part of a more effective approach to safer boarding.
A systems approach
Returning to RSSB research: two projects treat the PTI as a whole system issue. T1398 is looking at how different platform and train combinations can be grouped into boarding categories based on geometry and passenger capability. T1399 is considering what kinds of intervention are available, including train-based, platform-based, and mixed solutions, and how these might fit into real investment opportunities such as fleet replacement and/or station upgrades. Together, these projects will hopefully shift the debate in the right direction. Instead of asking what the perfect PTI would be in theory, they ask which changes are most likely to improve real boarding outcomes in the actual railway.
A system view matters because decisions about trains, stations, and operations are often made separately, even though passengers experience them as one journey. If the industry wants more reliable and more independent boarding, the same evidence base needs to inform vehicle specifications, platform renewals, station enhancement programmes, and assisted travel planning. Network history and fragmented decisions are reasons why the network has ended up with so much inconsistency. Better co-ordination will be needed if that inconsistency is to be reduced in a practical and affordable way.
Conclusion
Accessibility at the platform–train interface is not one problem with one answer. It is the result of an older railway, mixed traffic, varied platforms, tight physical constraints, and a very diverse passenger base. Lower-floor trains, especially with sliding or retractable steps, can make a real difference and should be part of future fleet strategy, but they will not deliver independent boarding everywhere on their own.
Better platform geometry, targeted physical works, improved stopping accuracy, and evidence-led prioritisation are all part of the picture as well. Full independence for every passenger at every location may not be realistic on all parts of a legacy mixed-traffic railway. Even so, there is clear scope for meaningful improvement. The challenge for the industry is to keep making practical changes that improve real journeys, rather than waiting for a perfect solution that may never arrive.
This article is based on a presentation given at a recent IMechE Rolling Stock Lifecycle Conference by RSSB’s Bridget Eickhoff.
The Elizabeth line – a modern challenge
When the railway into Heathrow Airport was built, it was decided to provide level access between platform and train. The original Class 332 trains had a floor height that would be compatible with 1,100mm-high platforms. Two platforms were raised to suit at Paddington and dedicated to this service.
Quite early on, the circa 75mm gap between platform and train footstep proved to be an issue and rubber deformable gap fillers were added. When the Crossrail project had to consider what to do, it decided on level access in the new build sections.
It was recognised that low floor trains would not be acceptable (even if they had been available at the time) because: (a) stepping up onto higher platforms would be undesirable, especially at Heathrow (luggage issues); and (b) reconstructing Heathrow’s five platforms to a lower height would not be practicable.
Hence the new build area has 1,100mm-high platforms and there is a step up from platform to train at all the Network Rail platforms, not all of which are at the nominal 915mm height. Some are lower.
This issue has come up again in developing the PTI design for the new Old Oak Common station where there is a desire to have 1,100mm-high platforms on the local line platforms at least to provide level access to Elizabeth line trains. Engineers seeking this solution have found that providing an acceptable gap to the Class 345 trains is challenging if clearance must be maintained for other trains to use the lines when the fast lines are closed (e.g., for engineering works). Moreover, the situation is likely to get worse in future as it is expected that future Great Western trains will be designed with lower floors to provide level access at 915mm high platforms.
This will continue to be an issue for the Elizabeth line, although perhaps there is some cause for optimism. The Swiss have developed gauge changing bogies for the Montreux to Interlaken trains which have to change track gauge at Zweizimmen. This gauge change includes raising the ride height of the carriages to accommodate higher platforms on the standard gauge network compared with those on the metre gauge system.
Perhaps an adjustable height train could be designed for the Elizabeth line when replacements are required in circa 2058?
Image credit: iStockphoto.com / ewg3d