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Level crossing insight

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On 10 April 2016, 1K77, the 12:04 Norwich to Cambridge Class 170 passenger service, struck a tractor and animal feed trailer at Hockham Road user worked crossing near Thetford in Norfolk while travelling at 87mph.

Although major level crossing accidents are very rare, this article provides an insight into how, in the quest for greater safety, lessons learned from accidents have shaped the configuration of those in use on the network today.

User worked crossings (UWCs)

This type of crossing is normally protected by gates or lifting barriers which are operated by the road user independently of the signalling system. Where the sighting distance is too short for users to see trains in sufficient time to cross safely, additional measures are required such as the requirement to call the signaller for permission to cross (UWC-T), safe use of which depends upon human activity. The signaller must carefully study the signal box indication panel or VDU screen, to judge the position of trains in the vicinity in order to ensure that there is sufficient time for vehicles to cross safely, and a clear understanding must be reached between signaller and crossing user.

In 2009, Bombardier produced a level crossing system which utilised a programmable logic controller (PLC) and operated at the stipulated Safety Integrity Level 3 (SIL3). EBI Gate 200 is designed to alert people to oncoming trains when crossing the line via public footpaths, farm crossings, bridleways and UWCs, and operates independently of the signalling system. The user presses the crossing request button that activates the system, displaying a red light with audible warning or green light as appropriate. It was installed at Hockham Road UWC, but a weakness in the documentation was subsequently discovered and the product acceptance certificate withdrawn. The installation was out of service at the time of the accident at Hockham Road in 2016.

Hockham Road UWC-T

At Hockham Road, the tractor driver was seriously injured and the train driver and four passengers suffered minor injuries. The tractor was destroyed and the train badly damaged, the train driver miraculously escaping serious injury.

Hockham Road is on the Norwich to Ely route, which was resignalled in 2012 with a DeltaRail (now Resonate) Integrated Electronic Control Centre (IECC) VDU signaller interface, known as the Thetford Workstation, located within the Cambridge Power Signal Box (PSB) Entrance-Exit (NX) panel operating floor.

The RAIB carried out an investigation into the accident and reported that the signaller gave permission for the tractor to cross when there was insufficient time for it to do so safely. The signaller lost awareness of the position of the train. Had the EBI Gate 200 system been operational, it would have probably prevented the accident.

The RAIB report also included much discussion on the ergonomics of the workstation and it emerged that there is a significant difference in the operation of the IECC workstation compared with the NX panel. In the latter case, the signaller is fully engaged with the task of setting and cancelling routes for each train, whereas the Thetford IECC work station operates mostly automatically with a greater potential for a signaller to lose concentration. It was also noted that the information displayed on the VDUs is not designed to help signallers judge when it is safe to allow a user to cross.

Issues being addressed include signaller training, competency, fatigue, engagement with the signalling task, and techniques for dealing with requests from UWCs. A modification to the EBI Gate system has been implemented. Following the incident, six screens have now been installed at the Thetford workstation and the local signal box instructions now mandate the use of detailed screens when authorising users to cross at a UWC.

Although a very serious accident, it should be appreciated that cases of signallers giving permission to cross when it is not safe to do so are extremely rare. User non-compliance is a predominant factor of accidents at UWCs, such as the collision between an articulated tanker and a Class 156 DMU near Sudbury in Suffolk on 17 August 2010 – the tanker driver did not use the telephone before driving onto the crossing.

Dock Lane UWC-T

Just two months after the Hockham Road accident, on 14 June 2016, a near-miss occurred when 2D81, the 12:07 Lowestoft to Ipswich Class 156 passenger train, passed over Dock Lane UWC-T, near Woodbridge in Suffolk, while a car was about to cross the line.

The RAIB investigation established that permission to cross was granted by the signaller who may have been diverted by the familiar and ‘light hearted’ nature of the call, a reference to the fact that the car driver was a frequent user of Dock Lane UWC, well known to the signallers, always asking for 72 seconds to cross with some form of wild animal! On the day of the incident she said: “Three rhino to go across – 72 seconds”.

The East Suffolk line between Ipswich and Lowestoft, previously deploying the 1980s Radio Electronic Token Block (RETB) system, was resignalled in 2012 with a GETS Modular Control System (MCS) signaller interface. There is one signaller on duty, managing calls from 28 UWC-Ts. In 2016, the signallers dealt with over 80,000 telephone calls in conjunction with requests to use UWC-Ts, averaging about 14 telephone calls from crossing users per hour. It was reckoned that signallers refuse permission to cross approximately 12,000 times a year, and analysis indicates that it is possible that the signallers could wrongly give permission to cross in the order of 36 times per year.

Signaller workload was discussed in the report in conjunction with the suitability of the types of crossing installed on the line. Another key factor is the long axle-counter block sections, stretching for several miles. The signaller must build up a mental picture of the exact whereabouts of trains within the control area, although there is an agreement that, if necessary, train drivers may be contacted via GSM-R to ascertain their location. Network Rail is considering a GPS-based Train Approach Warning System that provides the signaller with better information about train locations.

Automatic Half Barrier Crossings (AHBC)

The programme to replace some gated level crossings with AHBCs commenced in 1961, with a crossing at Spath on a now closed line near Uttoxeter in Staffordshire, and was intended to save staffing costs of gated crossings and, crucially, avoid delays to road traffic. Actuated by rail-mounted treadles, the crossing closure sequence provided a minimum warning time of 24 seconds from commencement of the illumination of the flashing red road lights to the arrival of the train.

AHBCs are not usually interlocked with the signalling system because, to do so, the trigger point would need to be much further from the crossing to enable the barriers to be lowered and the ‘distant’ signal cleared to green in good time. However, as no means is provided to check for obstructions on the crossing, linking the AHBC to signals would be mostly pointless, and the road closure time would be extended from typically 30 seconds to between three and five minutes or longer, leading to significant road user frustration and the temptation to zig-zag around the barriers and obstruct the crossing. Sadly, this is exactly what happened at Athelney AHBC on 21 March 2013 when a motorist was killed whilst zig-zagging. The barriers were down for an extended period.

By 1968, 205 crossings had been introduced when disaster struck. At Hixon AHBC in Staffordshire, on 6 January 1968, the 11:30 Manchester Piccadilly to London Euston locomotive-hauled express passenger train, travelling at 75mph, collided with a heavy road transporter carrying a 120-ton transformer over the crossing at 2mph with a police escort. Eleven people were killed and many injured. Neither the crew of the transporter nor the police escort knew the time sequence of operation of AHBCs or was aware of the need to telephone the signaller before crossing with a large slowly moving vehicle.

A public enquiry was held and the report discussed the risk of vehicles stalling on the crossing and the ‘another train coming’ situation, which could result in the barrier sequence being called by a second train just as vehicles were starting to move onto the crossing after the first train. Incidentally, the latter scenario resulted in a car being totally destroyed and the five occupants killed at Trent Road AHBC in 1968.

Prophetically, the provision of obstacle detection was discussed at length but ruled out. It stated: “AHBCs are a valuable answer to the needs of modern transport, and can be made acceptably safe without the introduction of obstruction devices linked with signal protection. These device, even if technically feasible, would be costly and involve the loss of most of the benefits for road traffic achieved by AHBCs.”

However, the report recommended ‘improvements’ which included extending the warning time from 24 to 32 seconds, provision of an outer strike-in point to cover the second train situation, provision of an illuminated ‘another train coming’ neon sign, the addition of a steady yellow preliminary warning light, plus various measures to improve road markings and profile and an update to the Highway Code.

The Hixon report also said that conversion of crossings should be “pressed forward at greater speed so that the public become familiar with the new equipment”. Alas, ‘Hixon Mods’ made AHBCs complex and costly, consuming significant S&T design, installation and testing resources and leading to a ten-year hiatus in new installations. A 1978 joint British Rail and Department of Transport committee report recommended the relaxation of some of the Hixon requirements with a reduction in warning time from 32 to 27 seconds and discontinuation of the neon ‘ATC’ sign, making them “cheaper to install and maintain without affecting their present excellent safety record”.

Ufton Nervet AHBC

Fast forward to 6 November 2004 and Ufton AHBC. The 17:35 London Paddington to Plymouth High Speed Train (HST) collided with a Mazda 323 car which was parked on the crossing and obstructing the Down line. A catastrophic derailment followed in which seven people died and many more were injured. The driver of the car is believed to have taken his own life.

Since that crash, there have been four more road-user deaths, and a near miss during engineering work with the barriers up and a train approaching. The crossing was replaced in December 2016 by a bridge costing £7 million.

The issue of obstacle detection was raised in the report and a separate study determined that integrating OD with AHBC and the signalling system was not viable. However, provision of OD would lead to an improvement in safety and efficiency at manually controlled barrier crossings (MCBs).

Automatic Open Crossing – Disaster at Lockington

Simplified automatic crossings without barriers were progressively introduced from the 1970s. Automatic open crossings, locally monitored (AOCLs) have a maximum permitted speed of 56 mph such that the train driver could stop short of an obstruction, hence the ‘L’ for locally monitored.

The 1978 report advocated a new type of crossing, designated AOCR. This was, essentially, an AHBC without barriers, with a maximum line speed of 75mph. ‘R’ stood for remote monitoring by a signal box, though this was limited to indicating the correct functioning of the equipment. There was no surveillance.

On 26 July 1986, a van was driven onto the AOCR crossing against the red lights into the path of the 09:33 Bridlington to Hull DMU. The train was completely derailed with the loss of nine lives and many others injured. During the course of the investigation, railway inspector Major A G B King highlighted the issue that “some motorists, after seeing the red lights flashing, act in a most irresponsible manner at the crossings. This results from stupidity, impatience, or a lack of appreciation of the hazards.”

The Lockington accident triggered a review of the safety of automatic open level crossings, conducted by Professor P F Stott, the outcome of which saw the end of AOCRs which were replaced by AHBCs or other appropriate types of crossing.

More recently, AOCLs have been upgraded with the addition of a barrier and re-classified AOCL+B. New installations are designed from scratch with barriers and classed as ABCL.

The Lockington report did consider that sunlight may have been a factor affecting visibility of the red lights, and was a key recommendation with Stott recommending that “British Rail should investigate the optical system to see whether it is possible to improve visibility by improving main beam brightness and reducing sun phantom effects”.

Visibility of the lights may have played a part in other incidents but only recently has suitable replacement technology come to the fore. LED lights are now used for the road red and yellow warning lights and barrier boom lights to achieve consistent and bright illumination, with the added advantages of lower current consumption and higher reliability in comparison with filament bulbs.

Obstacle Detection (OD)

OD is a recent development which facilitates full automation of the MCB crossing, making it one of the safest types of crossing and suitable for high-speed main lines. Signaller input is eliminated since the ‘Crossing Clear’ function is achieved by the OD, and ‘Auto Lower’, previously an optional extra at MCBs, is provided as standard.

Radar is the primary obstacle detector, using a SIL 3 device to detect vehicles, people, or large animals within the surveillance area. Associated with this is a complementary obstacle detector using infra-red LiDAR technology to scan an area below 500mm from the road surface. Approved for use on Network Rail are the Honeywell YD136 radar detector and Optex Redscan RLS3060 LiDAR.

Honeywell radar detector.
Honeywell radar detector.

Level-crossing predictor

With automatic level crossings, the disadvantage of a fixed strike-in point is that the actual warning time given to the user may vary significantly according to the speed of the train. To overcome this issue, a level-crossing predictor was first introduced between Norwich and Cromer when the line was resignalled in 2000. The GETS Harmon HXP-3 uses audio frequency track circuits to detect an approaching train, and the rate of change of the inductance of the rails is used to determine its speed and hence calculate the trigger moment to provide a constant warning time for each train. Another similar product is the Siemens Automation Wayguard WESTex GCP4000.

Motts Lane MSL, Witham, Essex – a complex case

Automatic level crossings (except MCB-OD) do not generally interface with the signalling system. However, if crossings are located close to junctions and stations where trains may start from rest, then crossings controls have to be integrated with the signal interlocking to ensure that warning times are not compromised or excessive.

On 24 January 2013, a cyclist disregarded the red stop light at Motts Lane and was hit and fatally injured by the 17:00 London Liverpool Street to Norwich express passenger train. The RAIB obtained evidence that users of the crossing habitually disregarded the warnings given by the lights and audible alarm.

During the investigation, it became apparent that the crossing warning time of 40 seconds is much longer than almost all users require to cross the line. Furthermore, the closure time was extended by at least 3.1/2 minutes by the use of a ‘non stopping’ setting for Down trains due to stop at Witham. When the signaller correctly selected ‘stopping’, the interaction of the Automatic Route Setting (ARS) system and the signal interlocking extended the crossing closure time for stopping trains.

Apparently the designer of the ARS system applied a rule in programming the ARS to delay operation of the level crossing, without realising that the controls within the Solid State Interlocking (SSI) already provided for such a delay.

The layout of signals at Witham is complex, necessitating approach-controlled aspects for Down stopping trains and thus causing delay to trains. The signallers discovered that this could be bypassed by selecting ‘non stopping’ for Motts Lane, thereby giving train drivers clear signals on the Down Main even though doing a station stop. Unfortunately, the signallers had not been briefed on the resultant increase in warning time.

The recommendations included a requirement for Network Rail to identify complex track and signalling layouts that may lead to excessive warning times at all automatic crossings, and a review of ARS data preparation processes where there is interaction with level crossing controls.

Motts Lane MSL was replaced with a bridge in 2014, costing £3.2 million.

The future

Improving safety at level crossings has exercised many minds over the years but it is apparent that technology is playing an increasingly important part in the ongoing challenge to provide cost effective and safe solutions.

Network Rail currently manages around 6,000 crossings on its network. That is after closing more than 1,000 over the past six years. However, while the safest level crossing is no crossing at all, and a further 250 are already earmarked for closure, there are some that simply cannot be closed, for a variety of reasons, and these have to be managed safely.

Despite the risks, some users and local authorities insist that ‘their’ crossings remain open. There is even a website – stopnetworkrail.org.uk – that claims to be “a resource for local groups fighting Network Rail’s aggressive policy of closing level crossings with little regard for their users”.

There is much still to be done.

This article was written by David Bickell.


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