Signalling Controls

Signalling controls named after locations.

Name	Description	Result of Accident
Colwich Controls	Preventing the display of flashing yellow junction indications when the signal immediately beyond the junction signal is at danger. This is in case the driver fails to recognise that the junction signal is maintained at yellow and does not step up to a less restrictive colour.	The driver of 86429 "The Times" on the 17.20 Liverpool-Euston on 19 September 1986 mis-interpreted the flashing yellow junction sequence leading up to CH.28 as meaning the route was set throughout the junction complex (which it didn't and it wasn't) and passed the next signal CH.23 at danger, crashing into 86211 "City of Milton Keynes" on the 17.00 Euston-Manchester which was legitimately signalled over the junction. 1 railwayman was killed and 75 passengers injured.
Foxhall Controls	Providing a position light junction indicator for the single route from a signal, where that single route applies through a set of facing points for the diverging route and track exists on the straight ahead route for which there is no legitimate signalled route. The provision of a junction indicator avoids the possibility of the driver believing they are heading 'straight on'.	D853 "Warship" overturned on Foxhall Junction on 27 September 1967 wrecking the 9.45 Padd-Weston after mis-interpreting the green aspect with no junction indication in R.180 as applying to the straight ahead route, when in fact it applied to a diverging route. One passenger was killed and 23 injured.
Lime Street Controls	The checking by virtue of track circuits being occupied and clear, that there is sufficient room in a partially-occupied platform to accommodate a second train. Track circuits of a known length are provided in the platform line and in rear of the previous signal to achieve this.	On 31 July 1924 the 2.40pm Euston-Liverpool arrived on platform 7 at Liverpool Lime Street and crashed into a light engine that was standign half-way down the platform. The signalman was not aware of the light locomotive's presence. A recommendation from this accident was the fitting of track circuiting, which has since developed further into using track circuits to 'measure' trains.
Moorgate Controls	The progressive lowering of trip cock activation arms at pre-set intervals to ensure a train is slowing as it moves towards buffer stops.	A southbound Northern Line train failed to stop at Moorgate on 28 February 1975 and crashed into the end wall of the tunnel, killing 43.
Raynes Park Controls	Ensuring that the contacts that allow an approach-released signal to clear are not so separate from the contacts that control the signal in rear to danger that a failure scenario could allow the approach-release to be satisfied and the junction signal clear while the previous signal showed green.	?
Tollerton Controls	Providing overlapping train detection sections at the boundary between detection systems (eg, track circuits to axle counters) or interlocking types (eg, RRI to SSI), where the section to be occupied to slower to react than the section to be vacated. Can also be achieved with a time delay.	?
Welwyn Controls	The preventing of sending of a second 'line clear' on an absolute block instrument until the berth track circuit of the home signal has become occupied and clear after the first 'line clear' OR a mechanical release release 'winder' has been operated. This avoids the possibility of a signalman giving a line clear in the belief a train has left the section when it hasn't and giving a second line clear.	On 17th June 1935 the signalman at Welwyn Garden City erroneously gave 'train out of section' for train 825A 10.53pm Kings Cross - Newcastle) to Hatfield No 8 when it had not arrived, and accepted train 826 (10.58pm Kings Cross - Leeds). Even though the signalman at Hatfield No 8 rang the signalman at Welwyn Garden City to enquire as to the suspiciously short time train on 825A had spent in the section, the signalman at Welwyn Garden City was adamant. As a result of the lack of locking preventing the block being cleared before a train arrives, an the signalman at WGC's inattention, train no 826 crashed violently into the back of train 825A, killing 13 and seriously injuring 29.