My SimulatorEngland / Railway Heritage

English Signal Box Simulator

Set the points. Clear the line.

Next train: -Served 0Mean delay 0 sProtection 0

Interactive 3D • Mechanical Signalling

SIGNAL CONTROLS

Select route:

Main line Siding

Signal:

Stop

Show linkages

Virtual demonstration only — not instructions for operating a real signal box. Trains cannot collide here: protection stops them.

Lab & science

Click a lever (or keys 1-9) to pull or replace it; the frame only lets a safe combination through. Drag to look around, wheel to zoom. S = set route, R = reset, P = pause, arrows = look.

Levers

Red = signals, blue = facing-point locks (FPL), black = points. Lever 8 is the distant (it warns of the home).

Frame messages

Setup

View

Express line speed

Service braking deceleration a

Distant placed before the home

Average gap between trains

Model-time speed

Graphics (High on every device; Low = 1x pixel ratio, no shadows)

Live readout (model values)

Braking test: how far before the home must the distant be for a stop?

Missions

The science

What you see

A mechanical signal box on a single line with a passing loop. Each lever works a signal arm, a set of points or a lock through rods and wires. The locking frame (the interlocking) makes some lever moves impossible, so a signaller cannot show two conflicting routes. A train driver sees a distant signal first, then the home signal, and needs real braking distance to stop.

Equations

Braking distance        s = v^2 / (2 a)
Time to stop            t = v / a
Distant placement       D >= v^2 / (2 a)  (else the home is passed at danger)
Speed curve to a stop   v(d) = sqrt(2 a d)  (d = distance to the stop point)
Block headway           h = (d + L) / v   (d = section length, L = train length)
Locking table           state s in {0,1}^9, move i allowed iff R_i(s, detectors) = null
Safety invariants       e.g. home main off => points W/E normal and locked

Assumptions & honest simplifications

Constant service deceleration; real brakes depend on load, adhesion, gradient and brake build-up time (ignored).
One-way (down) traffic only: the Oakridge section is a single block; real single lines also need token or block instruments.
The locking table is a simplified model written for this lab, not a copy of any railway's locking diagram. Lever colours follow the usual frame colour code loosely (red signals, blue locks, black points); the distant lever is shown red like the other signals here, and the frame is numbered 1-9.
A signal passed at danger is flagged and the train is stopped by protection in the overlap (emergency brake 1.1 m/s2); nothing collides.
Track layout, station and cottages are scenery, not a real place; Chelford and Oakridge are used as names only.

Independent numerical checks

The same checks run in node: node check.js (exhaustive state-space search of the locking table, Euler stop vs closed form, driver model).

Sources

Textbook railway signalling and interlocking principles (locking tables, facing-point locks, detection), kinematics of uniform deceleration, heritage-railway interpretation. Constants are model values [verify against a source before real use].

Loading simulation…