Eyes & Ears for Trains

London fog, source of endless inspiration to cinema scriptwriters, is just a headache to season-ticket-holders (British for commuters). On the 20 to 40 days each winter when visibility falls below 200 yards, the Reading, Chelmsford and Maidstone trains creep along at 30 m.p.h., often wait 20 minutes at junctions, reach London as much as two hours late. Last week British railway technicians were hard at work trying to do something about fog-foundered trains. They had two novel gadgets, both still in the experimental stage, which might make it possible for trains to keep up their usual clip in the thickest pea-souper.

Infra-red rays, which every photographer knows pierce fog, are the basis of one system, now being tested. Each signal box would have an infra-red generator; when its danger signal was up, a box would pour a constant beam of rays down the track. An approaching train would pick up the bad news on a photoelectric cell in the driver's cab.

The other gadget: sonar, radar's supersonic cousin. A sonar-equipped locomotive, by means of an oscillator and amplifier, would keep sending out whistle blasts pitched so high that nobody could hear them; but if a signal box ahead had its danger arm up, a reflector would send back the sound waves to the locomotive. There a microphone would detect the supersonic racket, a bell would ring (or a light flash), and the engineer would throttle down to his foggy-foggy due.

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