1.2 Points, Crossings, Switch Blades & Associated Hazards
Key Takeaways
Points and Crossings (P&C) or Switches and Crossings (S&C) are mechanical junctions that allow trains to transition from one track route to another.
A turnout comprises movable machined switch blades resting on lubricated slide chairs, fixed stock rails, stretcher bars, check rails, and a common crossing (frog).
Point machines operate automatically and remotely from signal boxes or Route Operating Centres without any local visual, audible, or advance warning.
Track workers must never step on, place hands or feet into, or straddle switch blades, stock rails, flangeway gaps, or moving stretcher bars due to instant crushing and amputation hazards.
Facing points diverge approaching trains when met from the switch toe, whereas trailing points converge two routes into one, governing route predictability and operational risk.
1.2 Points, Crossings, Switch Blades & Associated Hazards
Junctions and crossovers where trains move from one running line to another are formally termed Points and Crossings (P&C) or Switches and Crossings (S&C). From an engineering perspective, S&C installations are marvels of mechanical precision. From a track safety perspective, however, they represent the single most dangerous mechanical environment on the railway network.
Points contain powerful motors, motorized rodding, interlocking locks, and heavy steel blades that move without warning. Understanding how S&C functions, where the pinch points are located, and how to negotiate them safely is an indispensable element of Personal Track Safety.
Anatomical Components of a Turnout
A turnout is the basic S&C unit that allows a train to either continue straight on the mainline or diverge onto a secondary route. Every turnout consists of two distinct assemblies: the switch assembly (where the route choice is initiated) and the crossing assembly (where the rails physically intersect).
COMMON CROSSING (FROG)
┌───┐
STOCK RAIL ──────────────────────────────────────┘ └──────── STRAIGHT ROUTE
▲ NOSE
SWITCH BLADE 1 ─────────\ ┌───┐
\ └───┘
\ CHECK RAIL
\ ┌──────────────────────────────── DIVERGING ROUTE
SWITCH BLADE 2 ────────────/ │
│ CHECK RAIL
STOCK RAIL ──────────────────┴────────────────────────────────
▲ SWITCH TOE ▲ STRETCHER BARS & SLIDE CHAIRS
1. Switch Blades (Switch Rails)
The movable, specially machined rails that taper to a razor-thin point at the front end, known as the switch toe. The switch blades slide sideways across flat steel plates called slide chairs. Depending on which way the points are set, one switch blade is held flush against its adjacent fixed rail to direct the train's wheel flanges, while the other blade opens to leave a gap (the flangeway) for wheels to pass.
2. Stock Rails
The fixed, continuous outer running rails against which the movable switch blades rest when closed. The stock rail absorbs the lateral guiding force exerted by train wheel flanges as the train enters the curve.
3. Slide Chairs & Baseplates
Heavy steel or cast-iron support plates mounted directly on the P-Way timbers or concrete bearers. The upper surface of a slide chair is machined smooth and lubricated (or fitted with modern low-friction polymer rollers) so the switch blade can glide back and forth with minimal mechanical resistance.
4. Stretcher Bars (Tie Bars)
Transverse structural steel rods or tubular links connecting the pair of switch blades together across the four-foot. Stretcher bars perform two critical safety roles:
- They maintain exact track gauge between the two switch blades.
- They guarantee that both blades move in unison, preventing an open-blade gap that could derail a train.
5. The Common Crossing (Frog)
The V-shaped structural unit located where the inner rail of the diverging route crosses the inner rail of the straight route. The apex of the V is known as the crossing nose (formed by the point rail and splice rail). Because wheel flanges must cross the intersecting rail, an open flangeway gap exists across the crossing nose.
6. Check Rails (Guard Rails)
Short sections of raised steel rail mounted immediately inside the outer stock rails opposite the common crossing. Check rails act as safety guides: they catch the back of passing wheel flanges, holding the wheelset firmly in line so the opposite wheel cannot take the wrong flangeway gap or strike the sharp nose of the common crossing.
7. Flangeway Gaps
The narrow designed gap between running rails and check rails, and between an open switch blade and its stock rail. Flangeways allow train wheel flanges to travel through junctions unimpeded.
Point Actuation: Machines & Remote Operation
In modern railway networks, switch blades are rarely operated by hand levers. They are actuated by automated point machines:
- Electro-Mechanical Point Machines: Electric motors driving cranks and drive rods (the M63 and HW-series machines are common examples on the network).
- Hydraulic Clamp Lock Systems: High-pressure hydraulic cylinders mounted between sleeper cribs that pull the blade into position and physically clamp it against the stock rail with a positive mechanical lock.
- Electro-Pneumatic Actuators: Compressed-air cylinders used in dense terminal stations and high-frequency commuter yards.
Caution
Points Move Remotely and Without Warning Point machines are linked directly to computerized interlocking systems and are controlled automatically by Route Operating Centres (ROCs) or signal boxes tens or hundreds of miles away. Points can throw at any second without any warning horn, chime, or flashing light. Never assume points are inactive simply because there are no trains in sight.
Point machines exert far more force than a person can resist, and a blade can close in a few seconds. No one can stop or force open a moving point mechanism by hand.
Point Detection and Facing Point Locks (FPL)
Signalling systems will not allow a train to receive a green "proceed" aspect over points unless the switch blades are proven locked in the correct position:
- Facing Point Lock (FPL): A mechanical bolt that physically deadlocks the switch blades against the stock rail.
- Detector Rods & Microswitches: Electrical detection that proves the switch blade is closed against the stock rail within a very small tolerance. If ballast, ice or another object is trapped in the gap, detection fails, the signal stays at danger and trains are delayed, which is one reason you must never leave anything in a set of points.
Critical Track Hazards in Points & Crossings
Working around or walking through S&C presents lethal entrapment and stumbling hazards that must be actively avoided at all times:
| Specific S&C Component | Primary Hazard Mechanism | Mandatory Track Worker Safety Rule |
|---|---|---|
| Switch Blade & Stock Rail Gap | Instant crushing, mangling, and amputation of boots, feet, hands, or tools if the point machine throws remotely. | NEVER step inside the gap between switch blade and stock rail; never place hands or tools in the aperture. |
| Stretcher Bars & Rodding | Severe slips on grease; foot entrapment between moving stretcher bar and sleeper crib during point throw. | NEVER step on stretcher bars, drive rods, or detector links; always step completely over them onto clean ballast. |
| Flangeway Gaps (Crossing & Check Rails) | Boots becoming wedged in the narrow gap, pinning the worker directly in the path of incoming trains. | NEVER place boots into flangeway gaps; step cleanly across the rails without wedging heels. |
| Slide Chairs | Coated with heavy graphite grease, silicone lubricant, or roller brackets; extremely slippery underfoot. | NEVER step onto slide chairs or baseplates; step squarely onto the centre of sound sleepers or stable ballast. |
| Point Heaters (Gas & Electric) | Open gas burner flames, pressurized gas supply hoses, or high-temperature electric heating strips (burn hazards). | Watch footing around heater strips; never step on gas delivery pipes or electrical heating supply cables. |
STRICT SAFETY ZONES IN A TURNOUT
[ NO STEP ZONE ] [ SAFE STEPPING ZONE ]
┌────────────────────────┐ ┌────────────────────────┐
│ X Between Blade & Rail │ │ ✔ Clean Ballast Crib │
│ X On Stretcher Bars │ │ ✔ Centre of Timber │
│ X Inside Flangeway │ │ ✔ Fully OVER the Rails │
│ X On Greased Chairs │ └────────────────────────┘
└────────────────────────┘
The Entrapment Hazard
If a track worker places a foot or hand between an open switch blade and a stock rail, and the signaller sets a route, the machine will throw the blade shut. The tapered steel blade will wedge the limb against the solid stock rail with immense hydraulic or mechanical pressure. The victim cannot free themselves, cannot lever the blade open, and is pinned immovably in the path of approaching rail traffic. If you observe any person trapped in points, you must immediately treat it as an extreme life-or-death emergency.
Complex Trip & Stumbling Hazards
The area surrounding an S&C turnout is crowded with mechanical and electrical apparatus:
- Operating Rods & Escapements: Long horizontal steel rods traversing multiple sleeper cribs.
- Detector Rods: Sensitive mechanical links running from the rail toes to the point machine.
- Hydraulic Lines & Electrical Conduits: Flexible high-pressure hoses and armored cables crossing the cribs.
- Point Heating Equipment: In winter, electric strip heaters or gas burners run along the web of the stock rail to prevent ice accumulation. Gas feed pipes and electrical supply cables present dense snagging hazards.
When crossing through S&C, walk deliberately, keep your eyes on the ground, and step squarely across every obstacle rather than dragging your boots. HB1 states that if you have to cross the line you must not step on rails or sleepers or between the movable parts of points, and the PTS handbook tells you to walk ballast to ballast and take great care near points because they could move and trap your foot.
What the PTS Handbook Tells You About Points
- Points are generally worked from a signalling location and carry an identifying number. Quote that number when you report a fault or your location.
- The speed limit usually changes through junctions, but not always, so never judge a train's speed from the layout.
- Near stations the layout can be complex, with several sets of points and trains entering and leaving at the same time from different directions.
- Never assume which line a train is on, particularly if there are points nearby. A train that appears to be on one line can be routed across onto yours.
Facing vs Trailing Points: Route Implications
Railway points are classified based on the direction from which a train approaches them. Understanding this distinction is essential for predicting train movements and assessing collision risks:
FACING POINTS: Train approaches Switch Toes first -> Can diverge onto Route A or B
TRAIN ===> [TOE] ───┬─────────────── Mainline Route A
└─────────────── Diverging Route B
TRAILING POINTS: Train approaches Crossing first -> Converges from two lines into one
Route A ────────────┬─── [TOE] ===> TRAIN
Route B ────────────┘
Facing Points
In a facing turnout, trains approach the switch toe first. As the train reaches the fine tip of the switch blades, the setting of the points determines whether the train continues straight along the mainline or diverges onto the branching track.
- Operational Risk: High. If the points are damaged, gap detection fails, or the blades are forced open by track debris, an approaching train can derail or split the points (where different bogies take different tracks).
- Signalling Standards: Facing points on passenger lines are locked (for example by facing point locks) and detected before the signal can clear for a train to pass over them.
- Worker Awareness: When you see facing points set for a diverging route, you know any approaching train will veer across the junction into the diverging path.
Trailing Points
In a trailing turnout, trains travel from the crossing nose toward the switch heel and exit past the switch toes. Trailing points converge two separate lines into a single track.
- Operational Risk: Lower than facing points. If a train runs through trailing points that are set against it, the wheel flanges force the blades across as it passes. This is called "running through" the points and usually damages the stretcher bars, drive and detection equipment.
- Worker Awareness: Trailing movements mean trains can approach from either of the two converging lines behind you to merge onto the single line ahead.
Why is it strictly forbidden for any track worker to place a foot, hand, or tool between a switch blade and a stock rail, even on an apparently empty track?
The steel rail head contains sensitive electrical sensor coatings that degrade upon direct physical contact
The graphite lubricant applied to slide chairs releases caustic toxic fumes when compressed by footwear
Point machines require manual trackside hand-cranking before any personnel are permitted to walk across the junction
Point machines operate automatically and remotely without any warning, delivering immense clamping force that will instantly crush or amputate limbs
What is the primary safety function of check rails installed opposite the nose of a common crossing?
To restrain the back of passing wheel flanges and guide the wheelset safely past the flangeway gap at the crossing nose
To act as high-capacity electrical conduits returning 25 kV traction current to lineside substations
To absorb longitudinal thermal expansion from continuous welded rail and prevent lateral track buckling
To serve as friction-braking surfaces for runaway wagons within gravity marshalling yards
Facing points and trailing points differ in the direction from which trains reach them. Which statement is correct?
Facing points are always hand-worked from ground frames, while trailing points are always worked from a signal box
Trains reach facing points at the switch toe and can be diverted onto another route; trains reach trailing points from the crossing end and join one line
Facing points are only found on freight branches, while trailing points are only found on high-speed lines
Facing points never need locking or detection, while trailing points always need both
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