The Severn Tunnel train collision in 1991 was caused by a signaling error and the negligence of the sprinter train driver. The sprinter train entered the tunnel at a high speed after its signal incorrectly showed it was clear, and it collided with the slower high speed train inside the tunnel. The collision injured 183 people and seriously injured 5. The accident investigation found issues with the signal voltage and the response of S&T technicians to the malfunctioning signal contributed to the accident.

1. SEVERN TUNNEL TRAIN COLLISION

2. locationof accident : Severn tunnel ,London.
• Date of accident: 07/12/1991
• Country: United Kingdom
• Accident type: Front-Rear Collision.

3. 7 DECEMBER,1991.
• The disastrous day, there was an error in the signalling system.
• A HST (high speed train) entering the tunnel first, received driving permission for
careful driving through the tunnel.
• The motor vehicle train driving behind the HST did not stop at the signal in front of
the tunnel gateway, and proceeded through the tunnel at a considerable higher
speed than the HST. The motor vehicle train caught up with the first train
immediately before the western tunnel outlet, and was unable to stop in time.

4. TUNNEL
• This was the first sub sea railway tunnel, and it was first opened in 1886.
• The Tunnel was built by the Great Western Railway to provide a direct link between London
and South Wales.
• The Severn Tunnel is a double-track, brick-lined tunnel carrying the South Wales main line
of British Railways Intercity Great Western under the Severn Estuary between Pilning, on the
English side, and Severn Tunnel Junction (STJ).
• Its principal dimensions are:
• Length: 4 miles 628 yards
• Width: 26 feet
• Height: 20 feet from rail level to the crown of the Tunnel

5. HIGH SPEED TRAIN
• 1 B10,Intercity High Speed Train (HST) from Paddington to Cardiff, which entered
the Tunnel at approximately 10.20. This train consisted of front and rear power cars
and eight passenger coaches, weighing approximately 41 3 tonnes.
• There were 129 passengers and three employees on the train.

6. THE SPRINTER TRAIN
• 1 F08, the 07.00 Regional Railways Sprinter from Portsmouth Harbour to Cardiff,
which followed the HST into the Tunnel at approximately 10.26a.m.
• This was a Class 155 two-car Diesel Multiple Unit weighing approximately 77
tonnes.
• There were 168 passengers and two employees on this train.

7. SEQUENCE OF COLLISION

8. SEQUENCE OF COLLISION
• The high speed rain enters into tunnel at 10:20 a.m.
• The sprinter train enter into tunnel at 10:26 a.m.
• The collision occurs at 10:28 a.m.
•Resulting in:- 183 injured and 5 seriously
injured.

9. COLLISION HAPPENS BECAUSE
• The sprinter train driver Mr.Carpenter saw the signal N164.
• It means the route is clear and the sprinter train can enter into the tunnel.

10. CAUSES OF COLLISION
Did Driver Carpenter pass Signal N164 at Danger?
The driver of sprinter train saw Signal N164 change from red to green as the Sprinter
approached the signal at walking pace. He said he accelerated past the signal and was
travelling at "not far short of line speed“
when he saw the HST's tail-lights ahead. He immediately applied the emergency brake
and took his feet off the driver's safety device (DSD) - he assumed that he also closed
the power handle as a normal reaction.

11. WAS THERE AN ERROR BY THE S&T
TECHNICIANS?
(SIGNAL & TELECOMMUNICATION ENGINEERING DEPARTMENT)
• It seems clear that for much of the day of the accident the voltage at the detector
heads was out of tolerance, evidently due to the combined effects of cracking and
the low temperature. Taking the evidence at face value, it appears that the voltage
on the Down counter was out of tolerance. If the voltage was temperature-
dependent as suggested, it may well have been out of tolerance throughout the
morning, which should have prevented the signal from being cleared by re-setting
the evaluator.

12. AFTER COLLISION
• Implementation of the Emergency Plan went seriously wrong in several ways:
• The breaking of the Tunnel tell-tale wire did not produce an immediate response at
the Newport Panel because it was wrongly assumed to be due to a failure and not
to an emergency
• The precise location of the incident was not properly communicated in the early
stages, basically because no one checked the location quoted against the Tunnel
plan; most of the radio pagers issued to members of the BR Rescue Team failed,
apparently due to lack of maintenance, or possibly through not being switched on.

13. THE COLLISION IS BECAUSE OF
• The negligence at driver side
[because everyday at this time the sprinter train is stopping at
entrance of tunnel, and allow the high speed train to pass]
• Technical fault at signal
[the signal is not working properly due to high voltage]
• The negligence of S&T department worker
[they didn’t pay attention towards misbehaving of signal or high voltage problem]

14. CONCLUSION
• The conclusions of the Inquiry are:
• The accident was caused either by an unaccountable error on the part of the
Sprinter Driver or the S&T Technicians working in the STJ Relay Room; or possibly,
although this seems most unlikely, by a momentary or intermittent wrong-side
signalling failure which left no detectable trace, and has not recurred since the
accident.

15. ACCIDENT / INCIDENT INVESTIGATION
- GENERAL SAFETY PROGRAM
• Purpose
• To establish a method to handle accidents and incidents situations that occur on
campus property. These include both incidents and accidents which involve
employees and visitors, vendors, clients, spectators.
• Accident / Incident Investigations
• Accidents / Incidents must be investigated to an appropriate degree. As a result
we have two levels of investigations, a formal and an informal investigation.

16. FORMAL INVESTIGATIONS:
• Formal investigations are conducted for serious accidents. Both EHS / HW Officer
and the department and/or the sponsoring organization involved are participants
in the investigation.

17. INFORMAL INVESTIGATIONS BY SUPERVISORS:
• Since the supervisor/faculty advisor/organization representative is the
person charged with preventing accidents / incidents in his/her work
group or organization, that person should be actively involved in filling out
the appropriate form to determine the cause or causes of the
incident/accident and to implement corrective actions.
• Incident/accident forms may be downloaded from the Safety, Health,
Environmental web page for use in conducting the investigation.

18. INVESTIGATION PROCEDURE
• 1. Call or gather the necessary person(s) to conduct the investigation and obtain the
investigation kit.
• 2. Secure the area where the injury occurred and preserve the work area as it is.
• 3. Identify and gather witnesses to the injury event.
• 4. Interview the involved worker.
• 5. Interview all witnesses.

19. INVESTIGATION PROCEDURE
• 6. Document the scene of the injury through photos or videos.
• 7. Complete the investigation report, including determination of what caused the
incident and what corrective actions will prevent recurrences.
• 8. Use results to improve the injury and illness prevention program to better
identify and control hazards before they result in incidents.
• 9. Ensure follow-up on completion of corrective actions.

20. REFERENCE:-
• HM Railway Inspectorate, UK Railway inquiry report.
• UK Railway Accident Archives.
• Christian D, Francesca M, Ilaria Neri, Tunnel accident data and review of accident investigation
methodologies
• https://en.wikipedia.org/wiki/Severn_Tunnel_rail_accident
• accident investigation https://www.ccohs.ca/oshanswers/hsprograms/investig.html
• www.nsc.org/.../How-To-Conduct-An-Incident-Investigation.