Photo: the rail engineer.Farringdon platform extensions
In the last few years of employment with Network Rail, I spent a large proportion of my time dealing with standards for track engineering. In addition to dealing with the company’s own track standards and working with RSSB and other stakeholders on Railway Group Standards, the work included representation of the company, and on occasion the UK, at relevant European standards meetings.
One of the regular challenges from standards users was the suggestion that standards, whether company, Railway Group or international, restricted innovation and commercial activity to an unacceptable degree. The answer to such views was the same then as it is now. Standards are not there to be an obstruction to anything, their purpose is to offer guidance about how best to achieve the desired outcomes. Applied properly, standards assist people to avoid past mistakes and the traps inherent in conducting complex operations. Standards are intended to help people and organisations benefit from collective wisdom and experience.Non-compliance
To misquote the old saying, standards are there for the guidance of wise men and the mindless obedience of fools. Both Network Rail and RSSB have established ways for dealing with non-standard situations.
When it is clearly impossible or impracticable to comply with a standard, then the way to deal with a commercially driven standard is usually within the gift of the company or standard owner. The commercial risks of the possible options are assessed, and the most acceptable alternative selected. When the issue is a safety matter, the way to proceed is less obvious but must still be based upon the risks involved. RSSB will agree derogations or temporary non-compliances (TNCs) against standards where it is possible to agree an alternative approach to that specified but which still delivers a safety level equivalent to ordinary compliance. Companies such as Network Rail will employ a similar process.
The Group Standard derogation/TNC process is administered on behalf of the industry by RSSB standards committees. These are cross-industry bodies that reflect the broad interests of all stakeholders. Each committee specialises in a particular area, such as infrastructure or rolling stock.
Because the circumstances that lead to the need for a TNC or derogation are usually driven by unique or unusual factors, they are usually dealt with individually on a case-by-case basis. Whilst this may seem bureaucratic to some, in fact, if the procedures are managed and used correctly, it makes for a very flexible system. It will allow even the most arcane set of circumstances to be dealt with so as to deliver an economic, practical and safe outcome.
Of course, if it becomes clear that a particular set of circumstances is not as unusual as originally thought, resulting in a requirement for an excessive numbers of TNCs or derogations, that does call the standard concerned into question. In such cases the standard owner should doubtless review the document and revise it appropriately.
The essential approach to compiling standards and administering the TNC and derogation processes is a risk-based one. For Group Standards the major consideration is safety risk, of course, but even here there is a requirement to consider economic factors too. For company standards, commercial or financial risks will be considered a bigger factor, whilst safety still remains a top priority. Thus a Group Standard might lay down generic requirements for a track fastening to ensure that they are safe while the company standard might specify specific fastening types. Other types might comply with the Group Standard requirements but be rejected by the company on the basis of commercial considerations such as first cost or whole life cost.Farringdon for example
Perhaps that still sounds complicated, but in fact it works. RSSB has many examples of projects which have, by agreement, successfully implemented solutions that do not comply with the relevant standard. One such example is the recently completed project to extend the platforms at Farringdon Station in central London.
The object was, as regular readers of the rail engineer will know, to provide for 12 car trains on the Thameslink route as opposed to the original 8 car capability. Farringdon is an old station in a cramped location in a cutting. It is Grade 2 listed, which makes matters more interesting, and finally and completing the list of challenges nicely, it is used by both mainline trains and those of London Underground (LUL).
As Network Rail senior project engineer Paul Mitchison explained, the consequence of all these factors was that it was just not practicable to construct the new station in total compliance with either Railway Group Standards or LUL’s somewhat different standards.
A critical question affected by standards was the choice of location for the platform extensions. At the north end of the station is one of the steepest gradients on a British mainline railway, 1 in 29. To the south there is a curve with a radius down to 200 metres. Normally the Railway Group Standard would require that a station site would be selected to avoid both these features.
This was not practicable in this case and so it was decided to assess the risks of each problem, both to aid the decision about whether to extend to the north or to the south, and to allow a derogation from the standard to be successfully applied for for the chosen solution.
By involving the standards committees from the outset, and communicating closely with them throughout the process, the project was able to obtain the required derogation for the construction of the platform extension on the curved site at the south end of the station. It was demonstrated that the infrastructure standard requirements for platform gauge could be met even on the tightest curvature present.
Unfortunately, the operational standard requirement outlining the stepping distance from train running board to platform edge could not quite be met.However, it was successfully argued that, as the non-compliance was small, this was a much smaller risk than that of having platforms on a 1 in 29 gradient. Additionally, it was shown that the situation would be improved in future.
The new Class 700 rolling stock for Thameslink was to have lower running boards than the Class 319 and 377 units to be replaced, meaning that their stepping distance was going to be much improved and possibly even compliant with the standard. The problem was thus going to reduce in severity significantly as the new units came into service.Close columns
Another potential non-compliance issue concerned the columns supporting the train shed roof. In certain areas of the platforms it was not feasible to maintain a 4.5 metre clearance between these and the nearest rail. This meant that the Railway Group Standard required hefty collision protection structures around the columns; impractical and excessively costly to provide in the circumstances.
Discussion with the standards committees led to derogations, on the basis that the platform structures themselves gave adequate collision protection to the columns for the prevailing situation. The fact that trains would be passing at relatively low speed made it easier to reach agreement on this.
A third question arose over the matter of minimum headroom in public areas of the station. The Railway Group Standard headroom requirement was impracticable to achieve in certain areas of platforms 3 & 4.
The Grade 2 listing was obviously one constraint, and additionally the Transport and Works Act enabling the works made no provision for the alterations needed to increase the headroom.
The time and cost implications of obtaining the necessary consents and carrying out the works were prohibitive by anybody’s measure. Again, a derogation was granted, this time on the basis of the installation of “flow-by” structures at relevant points, to direct pedestrians around the areas of low headroom. Given that modelling had shown that the pedestrian flow capacity of the areas concerned would remain adequate with these structures in place, the derogation was granted.
Quite a number of other civil and track engineering standards issues were successfully managed in analogous ways by the project, RSSB and LUL, as were others affecting S&T and M&E engineering.
Despite the complexity of the project, the shared use of the station and the Grade 2 listing, all of the standards issues were successfully resolved, and in November 2011 the final “sign-off” was agreed by both RSSB and LUL. The extended station was opened for public use on time in December 2011.