Introduction
Switches and crossings make up about 5% of track miles on a mature network — and swallow roughly 24% of the maintenance budget and 23% of renewals. That number comes from seven years of Network Rail defect data. It tells you where your money actually goes. Get the switch wrong and you pay for it every year in speed restrictions, grinding passes and unplanned possessions. Get it right and it sits there quietly for two decades. This guide walks through what a railway switch is made of, the types worth specifying, the geometry that drives service life, and how to pick one for your track.
What Is a Railway Switch?
A railway switch is the movable part of a turnout. It is the assembly that steers a wheelset from one track onto another, and it is the only place on plain line where the running surface is deliberately discontinuous.
The switch works as a pair. Two tapered movable rails — tongue rails — sit against two fixed stock rails. When one tongue is pressed tight against its stock rail, the wheel flange follows it into the diverging route. The other tongue stands open to let the opposite flange pass.
People use “switch,” “points” and “turnout” loosely. The distinction matters when you order: the turnout is the complete assembly, the switch is the front end where movement happens, and the crossing is the rear end where the two routes cross.
Main Components of a Railway Switch
Tongue Rail and Stock Rail
The tongue rail is machined from a full rail section down to a knife edge at its toe. Head thickness increases gradually from the toe back to the heel, where it matches the parent section. The stock rail is the fixed running rail it beds against. The two are machined as a matched pair — swapping one without the other is a common and expensive mistake.
Heel Block and Heel Divergence
At the heel, the tongue rail is fixed and the two rails are held a set distance apart. That gap is the heel divergence. It is sized so a wheel flange clears the open tongue without grazing it. Too tight and you get flange contact and rapid lipping. Too wide and the switch angle steepens, which cuts permissible speed.
Slide Chairs and Baseplates
Slide chairs carry the tongue rail and let it move sideways under load. They take vertical wheel loads while offering low friction. Dry or worn slide chairs are one of the most frequent causes of a switch failing to close — a mechanical fault with an operational consequence.
Stretcher Bars and Point Locks
Stretcher bars tie the two tongue rails together so they move as one unit and hold the correct opening. The point lock holds the closed tongue against its stock rail under traffic. On modern layouts, clamp locks or in-bearer locks replace older external stretcher arrangements and reduce the number of loose components.
Point Machine
The point machine drives the throw and detects that the switch is fully closed and locked. Detection matters more than drive: signalling will not clear a route until the machine reports both blades in position.
Switch Sleepers and Fastenings
Switch sleepers are longer than plain-line sleepers and increase in length through the assembly. They carry higher bending moments and need elastic fastenings sized for the wider baseplates. Concrete, steel and hardwood all work; the choice usually follows what the rest of the corridor uses.
Types of Railway Switches
By Layout
- Simple turnout — one main line, one diverging line. Around 90% of all installations.
- Equilateral (symmetrical) turnout — the main line splits into two curves of equal radius. Useful where a yard throat has no dominant route.
- Three-way turnout — two switch sets in series, giving three routes. Common where land is tight, expensive to maintain.
- Slip switch — a diamond crossing combined with switches, so trains can either cross or transfer. Single and double variants.
By Blade Geometry
Straight-cut switches use a straight tongue rail and a fixed switch angle. Curved switches carry the diverging curve into the blade itself, which reduces the entry angle and lifts permissible turnout speed. Most modern high-speed layouts use curved blades for that reason.
By Rail Section
Ordinary switches machine the blade from standard rail. Thick web switches use a purpose-rolled asymmetric section with a heavier web, so the blade keeps its stiffness even where the head is machined thin. Thick web blades resist lipping and chipping at the toe far better and are now standard on high-traffic routes.
By Operation
- Hand-operated levers, still common in sidings and low-speed yards
- Electric point machines, the default on interlocked main lines
- Hydraulic drives, used where multiple blades throw together
- Spring or trailable switches, which let a trailing move push through and self-restore
Switch Geometry: The Numbers That Decide Performance
Turnout number is written as 1 in N — 1 in 8.5, 1 in 12, 1 in 16, 1 in 20. N is the cotangent of the crossing angle. Higher N means a flatter crossing and a longer, faster turnout.
The numbers a buyer should hold on to:
- Throw of switch — the distance the toe travels. Broad gauge minimum 95 mm, 115 mm recommended; new works commonly 115–160 mm.
- Check rail clearance — 44 mm nominal on broad gauge, 48 mm maximum in service.
- Junction of head clearance — minimum 38 mm.
- Speed — 1 in 8.5 turnouts carry the tightest diverging-route speed restrictions on Indian Railways, in the range of 10–15 km/h depending on the layout and instructions in force; 1 in 12 and flatter open up progressively higher speeds. Confirm the permitted value against your own operating instructions.
The pattern is simple: every step flatter costs more length and more money up front, and buys speed and service life afterwards.
How a Railway Switch Works
- The interlocking checks the route is clear and free of conflicting movements.
- The point machine drives the stretcher bars, sliding both tongue rails across the slide chairs.
- One tongue closes hard against its stock rail; the other opens to the set heel divergence.
- The lock engages and detection confirms both blades are home.
- The signal clears. Wheel flanges bear on the closed tongue and are steered into the chosen route.
- Through the crossing, the check rail on the opposite side holds the wheelset so the flange does not strike the crossing nose.
Applications of Railway Switches
- Main line junctions — flat turnouts, 1 in 16 and above, where diverging speed matters
- Station yards and loops — 1 in 8.5 and 1 in 12, chosen for compactness
- Freight terminals and ports — heavy axle loads, high-wear crossings, cast manganese preferred
- Depots and workshops — three-way and slip layouts to fit more roads into limited land
- Metro and light rail — short turnouts, often with in-bearer locks and shallow construction depth
- Industrial sidings — manual or trailable switches, minimal signalling
Where Switches Fail and Why
The failure data is unambiguous. In the Network Rail study, the switch panel accounted for 44% of all switches-and-crossings failures, and switch blade damage alone made up roughly one in five reported failures. Within blade failures, lipping — metal flowing over the edge of the running surface — accounted for 47%.
That tells you something uncomfortable. Most switch problems are not exotic. They are wear at the blade-to-stock-rail interface, and they are driven by three things: blade section stiffness, contact geometry, and grinding discipline. Two of those are decided at purchase.
Coexisting wear of stock and switch rail made up another 22% of switch panel reports — which is why matched-pair replacement, not single-rail replacement, is the right call.
How to Select the Right Railway Switch
- Start with diverging speed, not budget. Speed sets the turnout number, and the turnout number sets almost everything else.
- Match the rail section to the corridor. A 60 kg switch in a 52 kg corridor creates a transition joint you will maintain forever.
- Specify thick web blades on anything above moderate tonnage. The premium is small against the lipping it prevents.
- Check construction depth early on metro and viaduct work, before the sleeper layout is fixed.
- Ask for the laying plan and sleeper schedule with the quote. A supplier who cannot produce them at quotation stage will not produce them at delivery either.
- Confirm material certification for cast crossings and forged fittings against the standard you are being audited to.
FAQs
Is a switch the same as a turnout? No. The turnout is the whole assembly — switch, lead and crossing. The switch is just the movable front section with the tongue and stock rails.
What does 1 in 12 mean? It is the crossing angle expressed as a ratio. The two gauge lines diverge one unit laterally for every twelve units along the track. Higher numbers mean flatter angles and higher permissible speeds.
Why do thick web switches cost more? The blade is rolled from a purpose-made asymmetric section rather than machined from standard rail. That section keeps its web strength where the head is cut away, so the toe resists lipping and chipping under heavy traffic.
How long does a railway switch last? Service life depends on tonnage, turnout number and grinding regime. On heavily used layouts, blades are often replaced well before the crossing. Regular grinding and correct check rail clearance extend both.
Can a switch be trailed through? Only if it is designed to be. Trailable or spring switches restore themselves after a trailing move. Forcing a standard interlocked switch damages the stretcher bars and locks.
Conclusion
A railway switch is a small share of your track and a large share of your maintenance bill. The decisions that control that bill — turnout number, blade section, crossing material, fastening system — are made at specification, not in the field. Work through the geometry first, then the material, then the price.
Build Your Turnouts With Jekay International
Jekay International has been manufacturing railway track components since 1980, supplying railway developers and government bodies across Asia, Africa, Europe and the Americas. Our turnout systems cover switches, crossings, expansion joints, fish plates, base plates, elastic fastenings and insulated rail joints — backed by in-house forging, rolling mills, CNC planers, a flaskless foundry, high-pressure moulding and CMS welding.
That means one supplier, one set of tolerances, and full material certification on every component in the assembly.
Send us your turnout drawings or track parameters and our engineering team will return a laying plan, sleeper schedule and quotation. Contact Jekay International to get started.
