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LEDs Put Railroad Lighting on More Efficient Track

Photonics Spectra
Jul 1998
Max Glaskin

Using light-emitting diodes (LEDs) to replace colored tungsten filament bulbs for their signals could help railway companies cut costs and reduce risks for maintenance crews.

LED signals developed by Costas Tsakonas (left) and George Bearfield should cut costs and reduce risks for railway companies.

Engineering firm Signal House has developed LED signals that can meet the visibility requirements for this task and that are also expected to last 120 times longer than their traditional counterparts.

"Although LEDs are used in road traffic lights, the requirement for railways is much more demanding," said Signal House's Jim Wearing, who managed the system's development. The beam must be more intense so engine drivers can spot it up to a mile away at 140 mph. They also must be able to see it if they stop almost directly below the signal.

To achieve this, each Signal House device -- developed jointly by Costas Tsakonas and George Bearfield of Nottingham Trent University -- contains 114 LEDs, each with its own lens to ensure visibility at all angles.

The new lights also interface with fail-safe interlock system, which warns the system of failure and shuts off every signal on the route if one light goes out, letting the engine drivers know that they should stop their trains.

While incandescent bulbs last about six weeks, LEDs have a useful life of 14 years, which provides several benefits. Although the new signals may cost 60 percent more than existing signals, they will save money over time. In addition, train services are less likely to be halted by signal failure, and the hazardous task of replacing signals won't be required as often.

The LED signals are going through type approval testing, with the first system expected to be installed by the UK's Railtrack by the end of the year. Signal House hopes to sell millions worldwide, getting the payoff for the gamble it took when it began the project two years ago, when no manufacturers could make the blue LEDs vital for the green signals.

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