thumb|upright|Two-aspect signal at danger (stop) in the United Kingdom

A signal passed at danger (SPAD) is an event on a railway where a train passes a stop signal without authority. This is also known as running a red, in the United States as a stop signal overrun (SSO) and in Canada as passing a stop signal. SPAD is defined by Directive 2014/88/EU as any occasion when any part of a train proceeds beyond its authorised movement. Unauthorised movement means to pass either:

  • Environmental conditions
  • Inattention
  • Distraction
  • Misreading of an adjacent signal due to line curvature (a "crossread"), or sighting on one beyond
  • False assumptions based on familiarity and past situations either after passing a signal displaying caution or at a signal displaying danger.

Once applied, the DRA displays a red light and prevents traction power from being taken until the DRA is manually cancelled by the driver.

Collision prevention systems

Whilst the ideal safety system would prevent a SPAD from occurring, most equipment in current use does not stop the train before it has passed the danger signal. However, provided that the train stops within the designated overlap beyond that signal, a collision should not occur.

Train stops

On the London Underground (for example), mechanical train stops are fitted beside the track at signals to stop a train, should a SPAD occur.

Train stops are also installed on main line railways in places where tripcock equipped trains run in extensive tunnels, such as the on the Northern City Line where the Automatic Warning System and Train Protection & Warning System are not fitted.

Automatic Warning System

On the UK mainline, AWS consists of an on-board receiver/timer connected to the emergency braking system of a train, and magnets located in the center of the track. At each AWS site, a permanent magnet arms the system and an electromagnet connected to the green signal lamp disarms the system and a confirming chime is provided to the driver. If the receiver does not disarm within one second after arming, a warning tone sounds at the driver's desk and if it is not cancelled by the driver, the emergency brakes will be activated. A visual indication remains set to remind the driver that they have passed a restrictive signal aspect.

Train Protection & Warning System

On the UK mainline, TPWS consists of an on-board receiver/timer connected to the emergency braking system of a train, and radio frequency transmitter loops located on the track. The 'Overspeed Sensor System' pair of loops is located on the approach to the signal, and will activate the train's emergency brake if it approaches faster than the 'trigger speed' when the signal is at danger. The 'Train Stop System' pair of loops is located at the signal, and will activate the emergency brake if the train passes over them at any speed when the signal is at danger.

The deployment of TPWS is not universal; only those signals where the risk of collision is considered to be significant are fitted with it.

Flank protection

At certain junctions, especially where if the signal protecting the junction was passed at danger a side collision is likely to result, then flank protection may be used. Derailers and/or facing points beyond the signal protecting the junction will be set in such a position to allow a safe overlap if the signal was passed without authority. This effectively removes the chance of a side-impact collision as the train would be diverted in a parallel path to the approaching train.

SPAD indicators

thumb|SPAD indicator

right|thumb|50px|Animation demonstrating a SPAD indicator in action.

Prior to the introduction of TPWS in the UK, "SPAD indicators" were introduced at high risk locations (for example: the entry to a single track section of line). Consisting of three red lamps, they are placed beyond the protecting stop signal and are normally unlit. If a driver passes the signal at 'danger', the top and bottom lamps flash red and the centre lamp, which has the word "STOP" written across the lens in black, is lit continuously. Whenever a SPAD indicator activates, all drivers who observe it are required to stop immediately, even if they can see that the signal pertaining to their own train is showing a proceed aspect.

UK acronyms: SPAD / SPAR<span class="anchor" id="Signal passed at danger in the United Kingdom; Terminology and procedures"></span><span class="anchor" id="Acronyms: SPADs and SPARs"></span>

In the UK, incidents where a signal is passed at danger without authority are categorised according to principal cause. A SPAD is where the train proceeds beyond its authorised movement to an unauthorised movement. Other types are categorised as SPAR ("signal passed at red").

Prior to December 2012, the term "SPAD" applied to all such incidents, with a letter specifying cause.

  • A SPAD (formerly Category A SPAD) is where the train proceeds beyond its authorised movement to an unauthorised movement. where the train was standing at a danger signal and the driver moved past it.
  • SOY SPAD – "Starting on yellow" SPAD,

Driver obtains signaller's authority to pass a signal at danger

Once the train has been brought to a stand at a signal which is at danger, the driver should attempt to contact the signaller. If the signal cannot be cleared then the driver must obtain the signaller's authority to pass it at danger. Methods for contacting the signaller may include GSM-R cab radio, signal post telephone or mobile phone.

In the UK, the signaller can authorise a driver to pass a signal at danger when:

  • The signal is defective or disconnected
  • The signal cannot be cleared because signalling or level crossing equipment has failed
  • The signal is to be passed at danger for shunting purposes
  • The signal cannot be cleared because a train or movement which has reversed is then required to start from beyond that signal
  • An electric train is to pass the signal protecting an isolated section and proceed towards the limiting point
  • A train has been accepted using restricted acceptance because the line is clear only up to the home signal of the next signal box and the section signal cannot be cleared
  • In an emergency, and then only when authorised by the signal box supervisor or Operations Control, so that a train carrying passengers can enter an occupied section to use a station platform
  • An engineering train is to move towards a possession, or leave a line under possession at an intermediate point
  • A train is to pass the signal protecting engineering work to gain access to a station where the train is required to start back, or a line under single line working, or a siding
  • The line is to be examined to check that it is clear
  • A train is to proceed at caution through an absolute block section from the signal box in rear when a failed train has been removed
  • A train is to enter the section after a train or vehicle that has proceeded without authority has been removed, or the front portion of a divided train has passed through the section
  • A train is to enter the section to assist a failed train, evacuate passengers from a failed train, remove a portion of a divided train, or remove a train or vehicles that have proceeded without authority
  • Single line working applies
  • Working by pilotman or modified working applies

The driver and signaller must come to a clear understanding, and ensure they agree about how it is to be done. In the UK the signaller tells the driver of a specific train to pass a specific signal at danger, proceed with caution and travel at a speed that enables him to stop short of any obstruction, and then obey all other signals. If the signal is fitted with TPWS, the driver resets the Driver Reminder Appliance, pushes the TPWS Trainstop Override button in the cab, and proceeds cautiously through the section. If the train reaches the next signal without finding an obstruction, they must obey its aspect, at which point they can revert to normal working.

Driver passes a signal at danger under their own authority

If contact with the signaller cannot be made then the driver must not move the train, unless it is standing at one of the following signals:

  • A signal controlled from a signal box that is closed on absolute block line only.
  • An automatic signal where local instructions permit it, e.g. signals within tunnels on the Northern City Line.

After passing a signal at danger under their own authority, the driver must stop at the next signal (even if it is showing a proceed aspect) and inform the signaller of what they have done.

EU statistics of SPADs as precursors of accidents

{| class="sortable wikitable"

|+ ERADIS database on SPADs as precursors of accidents per million kilometers

! Area !! 2006 !! 2007 !! 2008 !! 2009 !! 2010 !! 2011 !! 2012 !! 2013 !! 2014 !! 2015 !! 2016 !! 2017 !! 2018 !! 2019 !! 2020 !! 2021 !! 2022

|-

| Austria || 0.099 || 0.077 || 0.101 || 0.131 || 0.070 || 0.033 || 0.067 || 0.080 || 0.072 || 0.255 || 0.378 || 0.398 || 0.553 || 0.768 || 0.630 || 0.848 || 0.834

|-

| Belgium || || 0.782 || 1.044 || 0.816 || 1.061 || 0.905 || 0.756 || 0.577 || 0.683 || 0.952 || 0.937 || 0.550 || 0.739 || 0.744 || 0.576 || 0.752 || 0.877

|-

| Bulgaria || 0.139 || 0.416 || 0.342 || 0.095 || 0.000 || 0.128 || 0.144 || 0.568 || 0.556 || 0.431 || 0.680 || 0.752 || 0.605 || 0.958 || 0.924 || 0.701 || 0.734

|-

| Switzerland || || || || 0.182 || 0.561 || 0.610 || 0.689 || 0.599 || 0.613 || 0.492 || 0.457 || 0.543 || 0.593 || 0.574 || 0.540 || 0.576 || 0.712

|-

| Channel Tunnel || || 0.765 || 0.542 || 0.708 || 0.525 || 1.071 || 1.042 || 0.168 || 0.713 || 0.374 || 0.241 || 0.610 || 0.606 || 0.253 || 0.769 || 1.302 || 0.694

|-

| Czechia || 0.377 || 0.170 || 0.149 || 0.239 || 0.487 || 0.529 || 0.496 || 0.485 || 0.525 || 0.562 || 0.716 || 0.763 || 0.815 || 0.840 || 0.886 || 1.001 || 0.988

|-

| Germany || || 0.693 || 0.728 || 0.354 || 0.341 || 0.441 || 0.385 || 0.361 || 0.451 || 0.463 || 0.490 || 0.506 || 0.566 || 0.519 || 0.510 || 0.577 || 0.564

|-

| Denmark || 9.387 || 1.283 || 1.378 || 3.311 || 2.859 || 2.664 || 2.198 || 2.231 || 1.833 || 1.943 || 1.943 || 2.292 || 2.257 || 2.708 || 2.390 || 3.008 || 3.562

|-

| Estonia || || 0.265 || 0.280 || 0.147 || 0.000 || 0.143 || 0.284 || 0.000 || 0.534 || 0.710 || 0.597 || 0.768 || 0.694 || 0.818 || 0.606 || 0.822 || 0.147

|-

| Greece || 0.052 || 0.050 || 0.047 || 0.255 || 0.059 || 0.239 || 0.086 || 0.000 || || 11.259 || 0.000 || || || 0.000 || 0.000 || 0.000 || 0.000

|-

| Spain || 0.502 || 0.501 || 0.576 || 0.500 || 0.466 || 0.408 || 0.408 || 0.408 || 0.406 || 0.423 || 0.468 || 0.577 || 0.460 || 0.519 || 0.498 || 0.421 || 0.574

|-

| Finland || 0.354 || 0.418 || 0.563 || 0.400 || 0.686 || 0.392 || 0.393 || 0.654 || 0.604 || 1.030 || 1.325 || 1.268 || 0.813 || 0.951 || 0.534 || 0.699 || 0.328

|-

| France || 0.069 || 0.212 || 0.229 || 0.264 || 0.231 || 0.255 || 0.238 || 0.293 || 0.302 || 0.241 || 0.304 || 0.319 || 0.413 || 0.537 || 0.599 || 0.584 || 0.466

|-

| Croatia || || || || || || || || 0.000 || 0.000 || 0.096 || 0.048 || 0.000 || 0.082 || 0.092 || 0.099 || 0.143 || 0.095

|-

| Hungary || 0.075 || 0.105 || 0.073 || 0.066 || 0.098 || 0.164 || 0.202 || 0.173 || 0.168 || 0.101 || 0.037 || 0.157 || 0.083 || 0.130 || 0.799 || 0.204 || 0.611

|-

| Ireland || 1.919 || 1.842 || 1.104 || 1.155 || 0.791 || 0.332 || 0.435 || 0.985 || 0.547 || 0.827 || 0.712 || 0.480 || 0.713 || 0.628 || 0.643 || 0.449 || 0.659

|-

| Italy || 0.064 || 0.041 || 0.055 || 0.043 || 0.031 || 0.038 || 0.063 || 0.051 || 0.064 || 0.056 || 0.070 || 0.085 || 0.065 || 0.103 || 0.098 || 0.107 || 0.080

|-

| Lithuania || 8.968 || 4.002 || 0.190 || 0.498 || 0.142 || 0.000 || 0.273 || 0.212 || 0.070 || 0.212 || 0.000 || 0.195 || 0.065 || 0.296 || 0.000 || 0.203 || 0.168

|-

| Luxembourg || || || || 0.124 || 0.490 || 1.241 || 0.571 || 0.444 || 0.666 || 1.633 || 0.345 || 1.233 || 0.805 || 0.927 || 0.641 || 0.856 || 0.628

|-

| Latvia || 0.234 || 0.108 || 0.256 || 0.214 || 0.361 || 0.108 || 0.159 || 0.228 || 0.158 || 0.323 || 0.061 || 0.192 || 0.118 || 0.196 || 0.259 || 0.270 || 0.357

|-

| Netherlands || 2.195 || 1.964 || 1.727 || 1.621 || 1.156 || 1.040 || 0.007 || 0.000 || 0.720 || 0.642 || 0.635 || 0.661 || 0.842 || 0.863 || 0.626 || 0.657 || 0.673

|-

| Norway || 1.646 || 1.540 || 1.494 || 2.426 || 2.497 || 1.265 || 1.091 || 1.360 || 1.377 || 1.179 || 1.251 || 1.260 || 1.367 || 1.319 || 1.127 || 0.937 || 1.246

|-

| Poland || || 17.993 || 11.825 || 0.062 || 0.059 || 0.128 || 0.147 || 0.157 || 0.300 || 0.276 || 0.320 || 0.386 || 0.431 || 0.410 || 0.381 || 0.591 || 0.552

|-

| Portugal || 0.611 || 0.488 || 0.575 || 0.296 || 0.150 || 0.591 || 0.667 || 0.717 || 0.821 || 0.444 || 0.862 || 0.471 || 0.522 || 0.219 || 0.757 || 0.783 || 0.646

|-

| Romania || 4.478 || 4.415 || 4.119 || 4.881 || 6.106 || 4.971 || 4.122 || 4.339 || 3.183 || 5.344 || 4.576 || 3.430 || 3.752 || 3.948 || 0.000 || 0.000 || 0.000

|-

| Sweden || 1.466 || 1.615 || 1.990 || 2.530 || 2.413 || 2.116 || 2.336 || 2.046 || 1.678 || 0.943 || 1.526 || 1.746 || 2.055 || 1.690 || 1.441 || 1.603 || 1.490

|-

| Slovenia || 0.790 || 0.835 || 0.746 || 0.659 || 0.531 || 0.246 || 0.302 || 0.000 || 0.390 || 0.325 || 0.141 || 0.409 || 0.000 || 0.099 || 0.296 || 0.000 || 0.094

|-

| Slovakia || 1.530 || 1.549 || 1.520 || 1.668 || 0.463 || 0.551 || 0.843 || 0.706 || 0.383 || 0.457 || 0.492 || 0.581 || 0.568 || 0.394 || 0.692 || 0.648 || 0.492

|-

| United Kingdom || 0.657 || 0.622 || 0.576 || 0.457 || 0.585 || 0.509 || 0.411 || 0.498 || 0.551 || 0.493 || 0.419 || 0.514 || 0.559 || 0.573 || 0.517 ||

|}

Accidents involving a signal passed at danger without authority

<!-- WP:NFCC violation: thumb|200px|The [[Southall rail crash in 1997 was a result of the driver of a Class 43 HST passing a signal at danger without authority. The high-speed train struck a freight train entering a goods yard and both trains derailed, resulting in 7 deaths and 139 injuries.]] -->

<!--Sort chronologically-->

{|class="wikitable sortable"

! Country !! Incident !! Year

|-

| United States || Norwalk rail accident || 1853

|-

| United Kingdom || Lewisham rail crash || 1857

|-

| Canada || St-Hilaire train disaster || 1864

|-

| United Kingdom || Hexthorpe rail accident || 1887

|-

| Denmark || Gentofte train crash || 1897

|-

| United Kingdom || Potters Bar rail accidents || 1898

|-

| United Kingdom || Slough rail accident || 1900

|-

| United States || Washington DC train wreck || 1906

|-

| Australia || Sunshine rail disaster || 1908

|-

| United Kingdom || Tonbridge accident || 1909

|-

| United Kingdom || Ais Gill disaster || 1913

|-

| United Kingdom || Ilford rail crash || 1915

|-

| Hungary || Herceghalom rail crash || 1916

|-

| United Kingdom || Charfield railway disaster || 1928

|-

| Germany || Genthin rail disaster || 1939

|-

| United Kingdom || Norton Fitzwarren rail crash || 1940

|-

| United Kingdom || Eccles rail crash || 1941

|-

|United States

|Lackawanna Limited wreck

|1943

|-

| United Kingdom || Potters Bar rail accidents || 1946

|-

| United Kingdom || Harrow and Wealdstone rail crash || 1952

|-

| United Kingdom || Luton rail crash || 1955

|-

| United Kingdom || Lewisham rail crash || 1957

|-

| United Kingdom || Dagenham East rail crash || 1958

|-

| United States || Newark Bay rail accident || 1958

|-

| United Kingdom || Coppenhall Junction railway accident || 1962

|-

| Netherlands || Harmelen train disaster || 1962

|-

| United Kingdom || Marden rail crash || 1969

|-

| Australia || Violet Town railway disaster || 1969

|-

| United Kingdom || Paisley Gilmour Street rail accident || 1979

|-

| United Kingdom || Invergowrie rail accident || 1979

|-

| United States || Philadelphia Conrail West Chester Branch collision || 1979

|-

| Poland || Otłoczyn railway accident || 1980

|-

| United Kingdom || Wembley Central rail crash || 1984

|-

| United Kingdom || Eccles rail crash || 1984

|-

| Canada || Hinton train collision || 1986

|-

| United Kingdom || Colwich rail crash || 1986

|-

| United States || Chase train collision || 1987

|-

| United Kingdom || Glasgow Bellgrove rail crash || 1989

|-

| United Kingdom || Purley station rail crash || 1989

|-

| Germany || Rüsselsheim train disaster || 1990

|-

| Japan || Shigaraki train disaster || 1991

|-

| United Kingdom || Newton rail accident || 1991

|-

| United Kingdom || Cowden rail crash || 1994

|-

| Canada || Toronto subway accident || 1995

|-

| Germany || Garmisch-Partenkirchen train collision || 1995

|-

| United States || Secaucus Train Collision || 1996

|-

| United States || Silver Spring train collision || 1996

|-

| Australia || Hines Hill train collision || 1996

|-

| United Kingdom || Southall rail crash || 1997

|-

| Australia || Beresfield rail disaster || 1997

|-

| Finland || Suonenjoki rail collision || 1998

|-

| United Kingdom || Spa Road Junction rail crash || 1999

|-

| United Kingdom || Winsford railway accident || 1999

|-

| United Kingdom || Ladbroke Grove rail crash || 1999

|-

| Norway || Åsta accident || 2000

|-

| Belgium || Pécrot || 2001

|-

| United Kingdom || Norton Bridge rail crash || 2003

|-

| Egypt || Qalyoub rail accident || 2006

|-

| Netherlands || Arnhem || 2006

|-

| United States || Chatsworth train collision || 2008

|-

| Belgium || Halle train collision || 2010

|-

| India || Badarwas train collision || 2010

|-

| Indonesia || Petarukan train collision || 2010

|-

| Germany || Saxony-Anhalt train accident || 2011

|-

| Netherlands || Sloterdijk train collision || 2012

|-

| United States || Goodwell, Oklahoma || 2012

|-

| Switzerland || Granges-près-Marnand || 2013

|-

| Romania || Cotești || 2014

|-

| Belgium || Hermalle-sous-Huy train collision || 2016

|-

| Portugal || Soure train crash || 2020

|-

| United Kingdom || Salisbury rail crash || 2021

|}

Accidents following a signal passed at danger with authority

Whenever a signal is passed at danger the driver is required to "proceed with caution, stop short of any obstructions, and drive at speed that will enable you to stop within the distance which you can see to be clear". Failure to do this has caused the following collisions:

  • – Roseville, 1950
  • – Stratford (London Underground), 1953
  • – Coppenhall Junction, 1962
  • – Wrawby Junction, 1983
  • – Glenbrook, 1999
  • – Vittorio Emanuele (Rome Metro), 2006

Accidents where the signaller incorrectly authorised a driver to pass a signal at danger

Except where permissive working is in use, interlocking usually prevents a train from being signalled into a section that is already occupied. When operational needs require it, this can be overridden, and provided it is carried out in accordance with the rules this is a safe practice. However, failure to follow protocol can result in a collision:

  • – Nashville, Tennessee, 1918
  • – Bucerdea, 1968
  • – Castlecary rail accidents, 1968
  • – Seer Green, 1981
  • – Jakarta, 1987
  • / – Zoufftgen, 2006
  • – Szczekociny, 2012
  • – Bad Aibling, 2016
  • – Thessaly, 2023

See also

  • Ding-ding, and away, British slang for a guard incorrectly giving permission to a driver to start away from a platform against a red signal.

References

  • Office of Rail Regulation
  • UK Health and Safety Executive - Signals passed at danger - Archived 12 February 2006.