Platforms, refuges and people

Most of this book so far has been about keeping structures clear of trains. This chapter is about keeping people clear of them. Track workers, inspectors and emergency staff walk beside the track, and when a train comes they must step to a place where it cannot reach them. On open track with a wide cess, the strip of ground beside the ballast, that is easy. Beside a long wall, in a cutting, in a tunnel or on a bridge, it may not be, and the railway must provide places of safety: refuges cut into the wall, handholds to steady a worker pressed against it, or at least signs that tell workers they cannot stand there while a train passes. At stations, the opposite problem arises: platforms are built deliberately close to trains so that passengers can step on and off, inside the safety margin every other structure must respect.

This chapter covers the provision of places of safety beside long walls, using the NSW standard for safety refuges and handrail devices as an example, sizes and spaces refuges, explains why platforms are a managed infringement, and calculates the warning distance a worker needs.

When a wall needs a place of safety

A short wall or a single pier leaves a worker room to walk around it; a long wall does not. ARTC’s NSW standard for safety refuges and handrail devices, BSS 01, applied to a wall structure, such as a tunnel, retaining wall or permanent fence, longer than 35,000 mm and within 4,500 mm of the track centreline. It started from the assumption that a place is safe unless it is marked otherwise, and pointed out that while staff would be expected to know where the safe places are, that cannot be assumed.

Figure 1Provision beside long walls by clearance from track centreline, as given in ARTC BSS 01

	Clearance from track centreline to the wall	Provision
Category 1	less than 3,500 mm	refuges required; where impossible, danger signs that no refuges are provided
Category 2	3,500 to 4,000 mm	handrail devices as a minimum
Category 3	4,000 to 4,500 mm	no physical protection; a safe zone indicated by signs
Category 4	more than 4,500 mm	no physical protection required

The categories simply follow the space that is available. Closer than about 3,500 mm, a person standing against the wall is too close to a passing train, so the wall must have recesses, refuges, they can step into. Between 3,500 and 4,000 mm, a person can stand against the wall but needs something to hold, so that the train’s air blast and the urge to step away do not unbalance them. Beyond 4,000 mm, a person can stand safely if they know to, so signs mark the safe zone. BSS 01 also called for warning signs at walls shorter than 35,000 mm where train sighting is severely restricted, normally complementing a warning light system.

Spacing and placing

A refuge is useful only if a worker can reach one before the train arrives. BSS 01 set a maximum spacing of 20,000 mm for refuges and handrail devices. On a single track with structures closer than 4,000 mm on both sides, they were to be provided on one side only, so that workers would always know which side to go to; on multiple tracks, they were to alternate from one side of the group of tracks to the other.

Refuge details

Figure 2Refuge details given in ARTC BSS 01

• Avoid: Floorat cess level or at most a 200 mm step up; level; no cables, pipes or other obstructions
• Avoid: Minimum size2,000 mm high, 1,500 mm wide, 700 mm deep
• Avoid: Extra contentswidth increased to keep the clear floor area if telephones or extinguishers are inside
• Avoid: Handholdprovided, to help staff keep their balance as a train passes
• Avoid: Handrail devicetwo vertical 40 mm pipes 1,000 mm apart, protruding 400 mm, from 900 to 1,800 mm above cess

In practice, a refuge that is too shallow, too high above the cess, cluttered with cables or blocked by vegetation is not a refuge. The details matter because workers use refuges in seconds, often in poor light, sometimes carrying tools, and sometimes in groups, and a refuge that works for one unencumbered person on a fine day may not work for two people with equipment at night in the rain.

The running case: the retaining wall

This is an illustration. The council’s road realignment needed a new retaining wall on one approach to the overbridge, beside the main line, 120 m long, its face 3,700 mm from the track centreline. Under the categories in BSS 01, that put it in Category 2, needing handrail devices as a minimum. At a maximum spacing of 20 m, a 120 m wall needs handrail devices at each end and at intervals of no more than 20 m between, 120 ÷ 20 = 6 intervals and 7 devices. The consultancy showed them on its drawings, with the cess level, the handrail heights and the 400 mm projection checked against the structure gauge so that the handrails themselves did not become an infringement. It also asked the infrastructure manager whether moving the wall to 4,000 mm, which would have needed only signage, was possible; the road geometry did not allow it.

Platforms: a deliberate infringement

Platforms must be close to trains. A gap of 200 mm or more between a train’s step and the platform edge, plus the kinematic allowances, would be a hazard to passengers, especially those with prams, wheelchairs or poor mobility. So platforms are built inside the safety margin every other structure must respect, close to the train’s static outline, and managed as an approved infringement.

ARTC’s code of practice for SA, WA and Vic described normal practice as locating platforms as close as possible to the train for passenger safety, allowing the platform to accommodate the swept envelope of the largest rolling stock using the route, and said that the minimum contingency gap at platforms should be zero, with site-specific risk assessment and possibly datum markers. The NSW standards placed platform clearances in a separate standard, BDS 16, which was not among the documents used for this book, so its values are not given here.

Because platform clearances are so tight, platforms are sensitive to everything that moves the train or the track: wheel wear, suspension condition, cant, track position and the platform’s own condition. Platform edges are measured regularly, and track beside platforms is maintained to tighter tolerances, often with datum markers to fix its position.

The gap passengers see

At a straight platform, the gap between step and edge is set by the train’s width and the platform’s offset. At a curved platform, centre throw and end throw make the gap vary along the train: on a platform on the outside of a curve, the middle of each car swings away from the edge and the gap widens there; on the inside, the ends swing away. Cant tilts the body towards or away from the platform. That is why curved platforms can have large, variable gaps, and why platform design and train design are coordinated.

Bridges and viaducts

A bridge is a long structure with nowhere to step off: the parapets or edges are close to the track, and below is a drop. Rail bridges therefore often carry walkways and refuge bays, projecting platforms at intervals where a worker can stand clear of a passing train. The same logic applies as beside walls: the spacing must let a worker reach a place of safety in the warning time available, and the refuge must be large enough, guarded against falls and kept clear. Where a bridge has no walkway or refuges, the safe-working rules usually require the line to be protected before anyone walks across it.

Tunnels

Tunnels combine every difficulty: close walls, darkness, noise that masks an approaching train, limited sighting and air pressure from trains entering. Refuges in tunnels are recesses in the walls at regular intervals, marked and often lit, and some tunnels have continuous walkways with handrails. They are also part of the emergency egress plan for passengers in a train that stops in the tunnel, which brings in the requirements of building and fire safety as well as track safety.

Air blast

A passing train pushes air ahead of it and drags air behind it, and close to the track the blast and suction can unbalance a person, especially near fast trains and in confined spaces such as cuttings and tunnels where the air cannot escape sideways. That is part of why a person standing against a wall needs something to hold, as the handrail devices provide, and why refuges have handholds. Loose objects, sheets of material and site hoardings near the track can be moved by the blast too, which is a reason temporary works are secured.

Signs and lighting

A place of safety must be recognisable. Refuges and safe zones are marked with signs that workers can see from the track, and, where light is poor, lit or reflective markings. BSS 01’s danger signs for walls with no refuges, warning workers not to stand during the passage of trains, are the last line of protection where nothing physical can be provided, and they are placed where workers will see them before entering the restricted length, not in the middle of it.

Platforms and people beyond passengers

Platforms protect passengers, but they also affect workers. A worker on the track beside a platform has the platform face on one side and the train on the other, often with very little space between, and the platform overhang may hide them from a driver. Track work beside platforms is planned with the line protected, and some platforms have recesses under their copings, or refuges at their ends, for workers caught by a train. The platform’s closeness to trains, which serves passengers well, makes it one of the most dangerous places for track workers.

Keeping places of safety safe

Places of safety decay like everything else. Vegetation grows into refuges, cess paths wash out, handrails corrode and come loose, signs fade or are removed, and new cables and cabinets are placed in exactly the spaces workers need. The infrastructure manager’s inspection regime includes refuges, handrail devices, walkways and signs, and changes beside the track, such as a new fence or a new cabinet, are checked for their effect on places of safety as well as on the structure gauge. A refuge is only a refuge on the day it is needed if it was kept clear every day before.

Warning time and sighting distance

A refuge is only useful if a worker sees or hears the train coming in time to reach it. The time needed is the time to stop work, gather tools and walk to the nearest place of safety; the distance at which an approaching train must be seen follows from the train’s speed.

Figure 3Sighting distance needed for a worker to reach safety

sighting distance = train speed × warning time

Train speed

115 km/h ÷ 3.6 ≈ 31.9 m/s

Warning time

15 s

1. sighting distance ≈ 31.9 × 15 ≈ 479 m
2. on the curve at the retaining wall, sighting is limited by the curve and the wall
3. where the sighting distance cannot be achieved, lookouts, warning systems or track closure protect the workers

The calculation shows why curves, cuttings and walls are dangerous places to work: they cut sighting distance just where places of safety are scarce. The maximum refuge spacing helps by limiting the distance to the nearest refuge, and so the time needed to reach it. The network’s safe-working rules decide how workers are protected; the infrastructure’s job is to provide places of safety they can reach.

People and the service space

The service dimensions of Chapter 6 partly serve people: room to walk beside the track, room for maintenance vehicles, room to stand. When service space is reduced at a constrained site, the reduction affects workers as much as machines, and the provision of refuges, handrails and signs may become necessary where it would not otherwise be. The consultancy’s retaining wall needed handrail devices because the road pushed the wall closer than the 4,000 mm that would have left a standing space.

A failure: the blocked refuge

This is an illustration. During a track inspection in a long cutting with refuges, an inspector stepped into a refuge as a train approached and found it partly filled with a cable drum and coiled cable left by a signalling contractor. There was just room to stand sideways, and the inspector was unhurt, but shaken.

The refuge had been used as storage. The infrastructure manager’s inspection regime was changed to check refuges for obstructions, and contractors’ site rules were amended to forbid storing anything in refuges, with the refuges marked so that they were recognisable as places of safety.

Exercise: a wall in a cutting

A retaining wall in a cutting is 85 m long, with its face 3,350 mm from the track centreline. Using the BSS 01 categories quoted in this chapter, what provision is required? At a maximum spacing of 20 m, how many are needed? If the wall could be moved to 3,600 mm, what would change?

At 3,350 mm the wall is closer than 3,500 mm, Category 1, so refuges are required. For 85 m at no more than 20 m spacing, 85 ÷ 20 = 4.25, rounded up to 5 intervals, needs 6 refuges, one at each end and four between.

At 3,600 mm the wall would be in Category 2, needing handrail devices rather than refuges, still at no more than 20 m spacing, so 6 handrail devices. This is an illustration; recesses in a retaining wall are costly to build, which is why the wall’s position and the provision for people are decided together early in design, against the current standard.