40706 Software glitch and category B SPAD risk Portsmouth area

August 2009 in Network Rail and Suppliers

Equipment Signalling South West

The potential for technical SPADs at three signals in the area controlled by the Havant signal box is cited as a risk by one reporter.

After resignalling work in the Portsmouth area, what has been described as a 'software glitch' is causing these signals to occasionally change their aspects unexpectedly. In practice, this can mean a double yellow turning back to red, leaving a driver without enough time to brake, and the risk of having a SPAD. The drivers of three train operating companies - First Great Western, Southern and South West Trains - are affected. The problem has been reported correctly on a number of occasions

The reporter states, for example, that when the level crossing gates go down at Bedhampton station, the protecting signal will be at danger, but one of the signals showing a double yellow can randomly revert to danger. It is understood that the problem could be remedied, but only with a 48 hour possession taken by Network Rail. There seems to be a problem diarising this because of tight route operating requirements. All these crossings have had a TPWS grid installed, and the reporter suspects this may have something to do with the signalling anomalies.
Please could Network Rail advise when this work is likely to take place? The locations of the signals where this is said to be a problem:

• signal HT 34, on the Up line, approaching Bedhampton station;
• signal HT 393, on the Down line, near the level crossing at Warblington; and
• at Cosham on the Down line (signal number unknown).

Response from Network Rail

The signalling centre at Havant was commissioned in October 2007 using Siemens electronic interlocking. This is the second such computer based interlocking produced by Siemens employed in this country but the first to require a level crossing interface to be employed.

Soon after commissioning a number of issues were identified that needed resolving and one of these was associated with the level crossing interface and the timing of checking circuits which could lead to changes of aspect and the resulting CAT B SPAD‟s.

The cause of the problem was quickly identified by the Siemens Engineers and appropriate modifications made to the data software which was tried and tested in the German workshops.

The required data changes were ready to be implemented over a year ago but the amount of testing required once installed required a wheels free possession for the whole of the Havant controlled area for 12 hours minimum.

Arranging this possession has not been easy as it required the cooperation of all train operating companies to agree to no train operation for a Sunday morning and early afternoon.

A date was eventually agreed with the TOCs on the 26th April this year but regrettably problems were encountered loading the software modifications; the original software had to be installed back in the system again, hence the problem has not yet been resolved.

However, Siemens engineers have now identified why the new data could not be loaded on the day in question and detailed plans are now proceeding to attempt another reload; this is likely to take place in September or October 2009. Mitigation measures have been applied to minimise the possibility of changes of aspect occurring during the interim period.