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Keep Calm and Think Blue

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Just over a mile south of Stirling station was what was once considered to be Scotland’s highest risk footpath crossing. St Ninian’s crossing was located on Millhall Road and, although it had been closed to road traffic for many years, it remained open for pedestrian use. Within just a two-minute walk from the town’s Braehead and Broombridge housing estates, this crossing was heavily used. Tragically, it had seen an atypical number of incidents, with one fatality and six near misses reported within the past six years.

Interestingly, calming blue lighting had been trialled at St Ninian’s crossing as part of an effort to reduce the increasing number of suicides on Scotland’s rail network. Network Rail experimented with this novel illumination after it proved successful in Japan, where it had been installed at stations on Tokyo’s Yamanote line.

With a reported four-fifths reduction in suicides there, trials were undertaken on the platforms at Gatwick station. This proved successful too, with reductions not only in the number of suicide attempts, but also in the level of antisocial behaviour.

At the time of its installation at St Ninian’s crossing in 2016, the number of suspected suicides in Scotland had doubled over the previous six months to fourteen, compared with seven in the same period in 2015. Network Rail said this had bucked the trend in the incidence of suicides that were falling across the rest of the UK.

Risk mitigation

The railway through Stirling is set to be electrified in 2019. With the prospect of faster and quieter trains using the route, Network Rail took the decision to replace the level crossing by providing a fully accessible footbridge. St Ninian’s has become the first public crossing to close in Scotland since Inchyra in February 2012 and just the second to close this century.

As part of Network Rail’s commitment to improve this type of crossing, Story Contracting was engaged to construct a bridge structure that would allow safe, unimpeded access for pedestrians, as well as wheelchair users and pushchairs. Design of the bridge was sub-contracted to Pell Frischmann Consulting Engineers. Its design also anticipates the installation of overhead line equipment as part of the forthcoming programme to electrify the Stirling, Alloa and Dunblane lines. The value of the bridge project to Story Contracting was £1.9 million.

The new fully accessible footbridge has ramps with resting points, as well as stairs. Its structure consists of a steel U-frame deck, ramps and staircases. As footbridges come, this one is large, with the access ramps stretching for some 80 metres along the line of the railway before doubling back, forming an intermediate landing, in order to gain the height required to clear the forthcoming overhead line equipment. This ensures that the ramp gradient is not greater than 1 in 20.

28-week project

Work on site began in January 2017 with the erection of fencing to delineate the railway boundaries, followed by soil-stripping a section of council-owned land to the east of the track. This facilitated the installation of a site compound, piling platforms and crane platforms.

The first stage of the permanent works construction was the installation of piled foundations – a phase of works that was completed five weeks ahead of programme. The piling work was sub-contracted by Story to Technik Ground Solutions, a specialist geotechnical company that provides micro-piling, mini-piling and ground engineering solutions.

The St Ninian’s footbridge is a substantial structure and the ground conditions were identified as being weak to a significant depth. Preliminary pile testing was therefore undertaken to ensure appropriate pile capacities were achievable within the weak ground conditions present.

Other challenges for TechnikGS included operations being conducted adjacent to active running lines and the imposition of vibration restrictions due to the proximity of the rail infrastructure. The works involved the installation of eighty low-vibration bottom-driven piles to depths of up to 20 metres. Compression and tension loads were 350kN and 125kN respectively. In all, 130 cubic metres of concrete and 18 tonnes of reinforcement were used to form the in-situ piles and 26 pile caps.

With the work being carried out very close to the live railway, TechnikGS made use of short mast rigs. Full-depth pile reinforcement was also installed in sections no greater than three metres to conform to the live rail fall distance restrictions. Multiple rigs were employed in order to complete the works within the required timescale.

With completion of the sub-structure, Story’s steelwork sub-contractor, M&S Engineering of Annan, was able to commence the installation of the superstructure elements. The steelwork was installed over four nightshifts using a 220-tonne crane.

In total, some 268.2 tonnes of structural steelwork have been incorporated into the design. To finish things off, a four-coat paint protection scheme was applied, involving 2,168 litres of two-pack epoxy paint.

Let there be light

The final section of work involved the installation of cabling and the provision of a comprehensive lighting system, which perpetuates the previously used calming blue light idea. The bridge, stairs and ramp sections are illuminated by two different types of lighting. Blue LED luminaire light units from French company LEC Lyon have been fixed to each SHS section of the balustrades on the stairs and ramps, whereas, across the bridge deck, the design plan specified LED inset lighting units. This has been achieved by installing ten LED Plan Bridge Strip Lights to the underside of the steeple cope of the bridge parapet.

A total of 278 blue LED luminaire units was called for in the scheme. To power these lights and comply with BS7671 (Requirements for Electrical Installations IEE Wiring Regulations – 17th Edition), it was necessary to run 2,235 metres of cabling of various diameters, combined with the various LED driver units. Four steel equipment cases are located at the top of the stair and ramp sections.

On the bridge approaches, fourteen Holophane illuminated bollards and a further 350 metres of cabling have been deployed. All of the bridge, ramp and bollard lighting is connected through the primary DNO cabinet and controlled via photocell.

During daylight hours, all of the lighting is inactive. Once daylight has gone, a photocell is enabled and the fourteen bollards, ten Design Plan lights and two PIR detectors switch on. The PIRs are programmed to keep the 278 blue luminaire lights working at 30 per cent of their capacity when no persons are detected. Once a person is detected, the blue luminaire light output is increased to 100 per cent in order to provide clearly lit walkways along the stairs and ramps.

Protection of the railway has been ensured by the installation of 170 metres of steel palisade security fencing, complete with maintenance access gates. Although the site is located near to housing developments, there are open areas on both sides of the line. This had the benefit of providing plenty of space for the project activities.

However, Story’s management team made a concerted effort to liaise with all residents, providing weekly updates to the progress and programme of works. Through these conversations, both Story and Network Rail felt that positive relationships were established and the project was delivered in a harmonious manner.

Crossings abolished

Network Rail opened the footbridge in July 2017. Simon Constable, head of route safety health and environment for the ScotRail Alliance, said: “The single most significant risk to public and passenger safety on the railway comes from level crossings. At Network Rail, we are committed to reducing this risk as much as possible by taking action at our highest risk crossings.”

By any standard, this footbridge is impressive. With its price tag of £1.9 million and with 6,800 man-hours of work involved on site, is it justified?

Simon Constable continued: “This closure of St Ninian’s level crossing in Stirling is important, as it has previously been identified as a high risk pedestrian crossing. With more, faster trains due to use this route in the near future, there was further justification to push for closure and to create a bridge in this location.”

Network Rail is working hard to improve safety at its highest risk level crossings. Where it is practical and affordable, it will close them or, where no closure can be agreed, it will seek to improve safety by introducing additional measures.

It’s impossible to place a value on a life, of course. Fortunately, we’ll never know what the statistics would have looked like at St Ninian’s had the level crossing been retained. If this bridge and its blue lighting saves just one family from the tragedy and heartache of a death, it will have been money well spent.

Hopefully, blue lights of a rather different nature will be a thing of the past at this location.



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