Rail colour signal claims put on the line

17 Jun 2002

Signal suppliers to UK rail operator Railtrack, and the company's own consultants on signal standards, have countered the operator's claims that its yellow signals comply with six-year-old recommendations of the international standards authority CIE (Commission Internationale d'Eclairage).

Railtrack's claims follow allegations by Opto & Laser Europe magazine that Railtrack has not acted on the 1994 CIE recommendation that the yellow used in rail signals is too close to red (OLE June 2000 p5). The colours could be confused by train drivers, it has been suggested, particularly in the case of the controversial signal 109 implicated in the London rail disaster of last year that killed more than 30 people. A red signal was passed leading to a head-on collision.

Railtrack standards for the colour of signals are based on a 26-year-old British Standard (BS 1376). In 1994 CIE said bluntly: "The present CIE-recommended yellow colour area extends too far towards red."

It called for a substantial redefinition of the colour domain for yellow. Replacing yellow signals across the country would cost Railtrack millions of pounds. The company says that it already complies with CIE standards.

But the sole supplier of signal lenses to Railtrack has told OLE that the figures Railtrack has been quoting to the media since the publication of OLE's revelations, only apply to certain elements of the signal.

Alan Povey, technical director of the sole supplier, Nazeing Glassworks, said that the Railtrack figures apply to lenses and filters. His company complies with these specifications and lens units are checked by recognized testing consultants such as Scientifics Ltd. He said that the complete packaged signal with lamps and reflectors would only have to comply with the BS 1376 standard putting the yellow colour outside the CIE recommendations.

Hugh Barton of Scientifics, consultant to Railtrack on signalling and specifications, said: "These issues are important and need to be discussed.

"I am not aware of any initiatives within Railtrack which address the CIE recommendations, nor whether the UK rail authorities were represented on the CIE committee in 1994. It is possible that standards and specifications may need to be amended."

Railtrack has been saying that the wavelength of its signals lie between a restricted range of 587 to 589.5 nm falling within CIE recommendations. The figures refer to an August 1974 specification BR 820, a railway-specific version of BS 1376, for filters and lenses only.

However Railtrack group standard RT0031 for colour signal yellow dated only last October clearly specifies Class B of BS 1376 for the finished unit which allows wavelengths of up to 592 nm, well outside the CIE limit and towards red.

"BR 820 is used only for signal lenses," said Hugh Barton. "And new standards do not apply to existing signals such as 109 at Paddington."

Safety experts for the RMT and ASLEF unions have told OLE that the subject of amending colour standards has never come up in any discussions with Railtrack.

Further information: phillip.hill@ioppublishing.co.ukStory courtesy of Opto & Laser Europe Magazine