1.1 Track Layout, Track Components & Permanent Way Terminology
Key Takeaways
Each running line has a name (for example Up Main or Down Goods) and a maximum speed, both shown in the Sectional Appendix.
Up normally means towards the principal city or town and Down means away from it, but bi-directional and single lines can have trains from either direction.
Running rails, sleepers, fastenings and ballast form the permanent way; the cess, four-foot, six-foot and ten-foot are names for spaces, not exact measurements.
PTS distances given "from the nearest line" are measured from the nearest running rail of that line.
The normal six-foot between two open lines is too narrow to give the required distance from both lines, so do not treat it as a position of safety unless your COSS has briefed it as one.
1.1 Track Layout, Track Components & Permanent Way Terminology
To work safely within the railway environment, every track worker holding a Personal Track Safety (PTS) certification must understand the physical structure and spatial geography of the railway. The railway track is an engineered structural system known throughout the railway industry as the Permanent Way (P-Way). It is designed to carry heavy axle loads while holding the rails at the correct gauge and alignment through heat, cold, vibration and braking forces.
Familiarity with permanent way terminology is not merely academic—it is a vital safety prerequisite. Worksite boundaries, safe walking routes, and emergency isolation limits are defined using permanent way terms. Misunderstanding the difference between the "four-foot" and the "six-foot" can lead to fatal positioning errors.
Note
This section follows chapter 1 of Network Rail's Guide to your Personal Track Safety (RT3170, Issue 11, 2024), the handbook issued to PTS candidates, together with Rule Book Handbook 1 (GERT8000-HB1). Your sponsor's current issued handbooks always take priority over any study guide.
Running Lines, Directions and the Sectional Appendix
A running line is a line used by trains to travel from place to place. Every running line has a name, such as the Up Main or the Down Goods, and a speed limit. Both are recorded in a document called the Sectional Appendix, which also tells you which lines are electrified and which way trains normally run. Your COSS uses it when planning the safe system of work, and HB1 requires anyone going on or near the line alone to know the maximum speed and normal direction of trains on every line.
- Up and Down: Up is normally towards the principal city or town and Down is away from it. On a double-track railway one line is used in each direction, for example the Down Main and the Up Main.
- Multi-track railways: busy routes may have four or more lines, often paired as Slow lines and Fast lines with different speed limits (for example 100 mph on the Slows and 125 mph on the Fasts).
- Bi-directional and single lines: trains can be signalled in both directions on a bi-directional line, and on a single line every train uses the same track. Trains can also be authorised to run in the "wrong" direction on a normally one-way line, which is called single line working.
- Points and crossovers let trains move from one line to another; they are covered in section 1.2.
- Sidings, depots and yards store trains and vehicles. They are not running lines, they may be managed by train or freight operators, and they are not usually shown in the Sectional Appendix.
- Mileposts stand beside the line, usually every quarter of a mile, so that people can identify their exact location. Mileages are given in miles and chains (80 chains = 1 mile; 1 chain = 22 yards, about 20.1 metres).
Never assume a train will come from the "normal" direction. HB1 and the PTS handbook both warn that trains can approach in the wrong direction on a single line, during single line working, or inside a possession.
The Anatomy of the Running Rail
The steel beams upon which trains ride are called running rails. Modern railway track predominantly uses flat-bottom rail (such as the European 60E-series profiles on main lines, or 56E1, the European designation of the older British BS 113A profile), named because the bottom flange is flat and rests directly on baseplates or resilient rubber pads. On historic lines, secondary routes, or certain switch configurations, you may also encounter bullhead rail, which has a rounded base supported in cast-iron "chairs" and secured with wooden or spring-steel wedges called "keys".
┌─────────┐
│ HEAD │ <-- Hardened steel wheel contact surface
└───┬─┬───┘
│ │
│ │ <-- WEB: Vertical shear support
│ │
┌───┴─┴───┐
──┴─────────┴── <-- FOOT: Wide base distributing load
A flat-bottom rail cross-section consists of three distinct zones:
- The Rail Head: The top bulb of the rail. The crown of the head provides a hardened, smooth running surface for conical train wheels. The top inner corner is known as the gauge corner—the critical contact point where wheel flanges bear laterally to guide the train along curves.
- The Rail Web: The relatively thin vertical stem connecting the head to the base. The web acts as a beam web, resisting vertical bending and shear stresses while keeping the rail lightweight.
- The Rail Foot (Base): The wide, flat bottom flange. The foot distributes the concentrated wheel load across a wider surface area onto the sleeper baseplate or pad, preventing the rail from cutting into the sleeper under heavy traffic.
Standard Track Gauge
In the United Kingdom, standard track gauge is 1,435 mm (equivalent to 4 feet 8½ inches).
- Measurement Point: Gauge is measured perpendicularly between the inner running faces (the gauge faces) of the two running rails at a specific datum line 14 mm below the top of the rail head.
- Engineering Importance: Consistent gauge prevents train wheelsets from climbing the rail or dropping between rails. On tight curves, gauge may be widened slightly (by a few millimetres) to prevent long-wheelbase freight bogies from binding, but tight tolerances are maintained across the network.
Sleepers (Ties) and Resilient Fastenings
Rails cannot sit directly on rock or soil. They are clamped to transverse supports called sleepers (known internationally as ties). Sleepers preserve track gauge, distribute wheel loads from the rail foot into the ballast bed, and resist lateral and longitudinal track movement caused by train braking and thermal expansion.
| Sleeper Material | Typical Use | What It Means for You on Site |
|---|---|---|
| Pre-stressed concrete | Most plain line on main routes | Very heavy; never lift or move one without the correct plant or team method. |
| Timber (often hardwood or treated softwood) | Switches and crossings, bridges, some older track | Can be slippery when wet and may be treated with preservatives; wear the gloves your task briefing specifies. |
| Steel | Some secondary and lightly used lines | Steel parts need insulated fastenings where track circuits are used, which is one reason you must never lay metal objects across the rails. |
Warning
Metal Across the Rails Can Change Signals The PTS handbook warns that placing a metal object, such as a measuring tape or chain, across both rails can operate the signalling equipment and change a signal aspect in front of a driver. Keep metal tools and materials clear of signalling equipment and at least 0.3 metres (1 foot) from an axle counter head.
Rail Fastenings: The Pandrol System
Modern UK track uses resilient spring-steel clips to clamp the rail foot firmly against the sleeper. The most widespread brand across Network Rail is Pandrol:
- Pandrol 'e-Clip': A coiled spring-steel rod driven into a cast-iron shoulder embedded in the concrete sleeper. Applied and removed with a panpuller tool or specialized machinery.
- Pandrol Fastclip: A pre-assembled, captive fastening system where clips remain parked on the sleeper shoulders during transport and are mechanically pushed onto the rail foot during installation.
- Insulators & Pads: High-density polyurethane or EVA rubber pads sit beneath the rail foot to absorb impact shock and provide electrical insulation between rails, preventing signaling track circuits from leaking current through the sleepers.
The Ballast Bed & Drainage
The ballast bed is the layer of crushed stone in which the sleepers are embedded. Far from being random gravel, railway ballast is an engineered aggregate produced to strict specifications for hardness, shape and size.
- Rock Specification: Hard, angular crushed stone (such as granite) graded to a specified size range. Angular stones interlock when the track is tamped, which rounded gravel cannot do.
- Load Distribution: Spreads the concentrated load from each sleeper down onto the formation beneath, so that the ground is not overloaded.
- Track Anchorage: Resists lateral forces generated by curving trains and prevents continuous welded rail (CWR) from buckling under summer heat expansion.
- Rapid Drainage: Allows rainwater to drain instantly away from the rail head and sleeper seats into lineside cess drains, preventing mud pumping and subgrade liquefaction.
[Cess] <--------- TRACK CROSS-SECTION ---------> [Cess]
┌─────────┐ Rail 1 Rail 2 ┌─────────┐ Rail 3 Rail 4 ┌─────────┐
│ Cess │ │ │ │ Six- │ │ │ │ Cess │
│ Walkway │ ───┴───────────┴─── │ Foot │ ───┴───────────┴─── │ Walkway │
│ │ [=== Sleeper ===] │ Space │ [=== Sleeper ===] │ │
└─────────┴────────────────────────┴─────────┴────────────────────────┴─────────┘
░░░░░░░░░░░░░░░░░░░░░░░░ BALLAST BED (CRIBS & SHOULDER) ░░░░░░░░░░░░░░░░░░░░░░░░
████████████████████████ SUBGRADE & FORMATION LAYER ████████████████████████████
Ballast Zones
- The Ballast Crib: The volume of crushed stone packed between adjacent sleepers. Crib ballast must be kept full and level with the top of the sleepers to provide longitudinal restraint against track creep.
- The Ballast Shoulder: The stone extending outwards beyond the sleeper ends. It resists sideways movement of the track and is often steep and loose underfoot, so take care when stepping off it.
- Ballast Depth: A specified depth of clean ballast sits under the sleepers to drain water and spread the load. Disturbed or freshly tipped ballast is soft and unstable to walk on.
Permanent Way Spatial Geography: The Four Foot, Six Foot, Ten Foot & Cess
When walking or working on the railway, these four terms tell you exactly where you are. HB1 notes that they are terms, not exact measurements. You must know them thoroughly:
1. The Four-Foot
The space between the two running rails of one line. Standing in the four-foot puts you directly in the path of trains. Only go there when your safe system of work allows it. The PTS handbook says that when walking alone you should use the walking route or the cess and step into the four-foot only if absolutely necessary, for example to avoid an obstruction, for the shortest distance possible.
2. The Six-Foot
The space between a pair of lines when they are the normal distance apart. In normal double track it is only about two metres wide.
Important
Do Not Treat the Six-Foot as a Position of Safety A position of safety must be at least 1.25 metres (4 feet) from the nearest line on which a train can approach, or 2 metres (6 feet 6 inches) where the speed is over 100 mph. A normal six-foot cannot give that distance from both lines at once, and trains on both lines can pass you at the same time. Do not use it as a position of safety unless your COSS has specifically briefed it as one.
3. The Ten-Foot (The Wide-Way)
Where there are three or more lines, a wider space is sometimes provided between two of them. This is the ten-foot or wideway. Despite its name, HB1 points out that this distance may be less than 10 feet. Only treat part of it as a position of safety if it gives the required distance from every line on which a train can approach and your briefing identifies it.
4. The Cess
The area alongside the railway, outside the outermost running rail. Where it is wide enough and free of obstructions, the cess is the usual walking route and often contains the position of safety. Remember that much of the cess is still on or near the line (within 3 metres of a line), so the track safety rules still apply there.
| Trackside Term | Where It Is | Typical Use | Key Safety Point |
|---|---|---|---|
| The four-foot | Between the two rails of one line | Track work under a safe system of work | Directly in the path of trains; avoid unless the safe system allows it. |
| The six-foot | Between a pair of lines the normal distance apart | Crossing between lines when arranged | Too narrow to be a position of safety from both lines. |
| The ten-foot / wideway | Wider space between two lines of a multi-track railway | Equipment, sometimes a walking route | May be less than 10 feet wide; check the briefing. |
| The cess | Alongside the railway, outside the outer rail | Usual walking route and position of safety | Still on or near the line within 3 metres of a line. |
Cant (Superelevation) & Curved Track Geometry
When a train travels around a horizontal curve, centrifugal acceleration exerts an outward lateral force on the train body and wheelsets. To counteract this force, track engineers elevate the outer rail above the inner rail. This height difference is called cant or superelevation.
- Equilibrium Cant: The exact cant value at which the outward centrifugal force is perfectly balanced by the inward gravitational component at a specific train operating speed. Passengers feel no lateral forces.
- Cant Deficiency: High-speed trains travel faster than the equilibrium speed, meaning the outward centrifugal force is slightly greater than the cant tilt. Network Rail standards cap cant deficiency to prevent passenger discomfort and rail wear.
- Cant Limits: Network Rail track standards limit how much cant can be applied, so that slow or stopped trains are not tilted too far towards the inside of the curve.
OUTER RAIL (ELEVATED)
┌─────────┐
│ HEAD │
└───┬─┬───┘
│ │ ▲
│ │ │ CANT
INNER RAIL ┌───┴─┴───┐ │
┌─────────┐│ FOOT │ ▼
│ HEAD │└─────────┘
└───┬─┬───┘
│ │
┌───┴─┴───┐
│ FOOT │
──┴─────────┴─────────────────────────────── (Horizontal Datum)
Hazards of Cant for Track Personnel
- Sloping Ground: Walking across or along canted track means walking on tilted sleepers and steep ballast shoulder slopes. Under wet or icy conditions, slips and falls directly toward the inner rail are common.
- Reduced Sighting Distance: Curves inherently limit how far down the track you can see. If standing on the inside of a curve, high-sided freight wagons or lineside vegetation can block the view of an approaching train until it is seconds away.
- Train Tilt Towards the Inside Rail: Trains navigating canted curves tilt inward toward the low rail when traveling at slower speeds or stopping, significantly reducing lineside clearance on the low-rail side.
Gradients & Mileage Markers
Railway tracks are rarely completely flat. Gradients express vertical elevation changes along the route:
- Notation: Expressed in the UK as a ratio of horizontal distance to vertical rise or fall (such as 1 in 100, meaning the track rises or falls 1 metre for every 100 metres travelled). A flat track is designated as LEVEL.
- Gradient Posts: Situated lineside with two sloping wooden or metal arms. If an arm points downwards, the track falls in that direction; if it points upwards, the track rises.
- Mileposts & Quarter-Mileposts: Positioned lineside along the cess every quarter of a mile. Mileage is recorded in miles and chains (1 chain = 22 yards / 20.12 metres; 80 chains = 1 mile). When reporting an incident or emergency to the signaller or Electrical Control Operator (ECO), give the line name and the nearest milepost, signal number, bridge number or structure number so that they know exactly where you are.
What is the standard track gauge on the UK national rail network, and where is this dimension measured?
1,435 mm (4 ft 8½ in), measured between the inner gauge faces of the running rails 14 mm below the top of the rail head
1,524 mm (5 ft 0 in), measured between the outer web surfaces of the running rails at baseplate level
1,410 mm (4 ft 7½ in), measured between the centre points of the two rail head crowns
1,600 mm (5 ft 3 in), measured across the outer running edges of the sleeper baseplates
Why should you not treat the normal six-foot between two open lines as a position of safety?
The six-foot is reserved for conductor rails and point rodding
It cannot give the required distance from the nearest rail of both lines at once, and trains can pass on both lines together
The ballast in the six-foot is uncompacted clay that cannot support a person
Track circuits fail whenever anyone stands in the six-foot
The PTS handbook gives a distance "from the nearest line". From which point is that distance measured?
The centre line of the four-foot of that line
The outer edge of the ballast shoulder
The railway boundary fence
The nearest running rail of that line
Sections you finish are checked off in the contents.