Fogbrooms to the Rescue

Ordinary hazards of driving are compounded in New Jersey, where meteorology, topography and industrial air pollution often produce dense fogs that suddenly blot out the road ahead. Fog is so familiar a problem in some sections of the state that permanent electric signs have been erected along the New Jersey Turnpike to flash warnings of fog and to cut speed limits. But New Jersey motorists may soon have a clearer view. By borrowing a discovery used to produce water in Chile, state transportation officials hope to be able to sweep long stretches of highway clear of fog.

Like New Jersey, Chile has dense fogs, which move in from the Pacific nearly every evening. Even so, some of the country's northern areas are among the most arid in the world, receiving practically no rainfall despite their moisture-laden atmosphere. Observing that the fog collected into drops on nylon lines, scientists at the Northern University of Chile in Antofagasta constructed wood and metal frames strung with vertical strands of nylon and set them up on nearby hills. As the fog was blown through the frames by the evening wind, it formed water droplets on the strands that dripped into receptacles below, quickly filling them. With enough frames, the Chilean scientists believe they can supply the water needs of a medium-sized city.

Half Mile of Nylon. This sounded good to fog-conscious Wesley Bellis, research director of the New Jersey department of transportation. He set up a research group, which finally evolved a "fogbroom," a 30-in. by 48-in. aluminum frame strung with a half mile of nylon thread and rotated at 86 r.p.m. by a base-mounted motor. In a research chamber in which a prime New Jersey fog can be simulated, a row of fogbrooms substantially thinned a test fog in a minute and completely cleaned it up in five minutes.

Bellis and other scientists think that the moving nylon filaments jog the minute fog particles together, causing them to combine into water droplets large enough to drip down the threads. To test the brooms outside the laboratory, the New Jersey researchers have set up 20 in a field outside Trenton and equipped them with photoelectric devices that start their motors when a fog settles in. If they effectively clear a corridor through the fog, the devices will probably first be placed in operation along a stretch of highway five miles west of the Lincoln Tunnel that is frequently shrouded in fog.

Fogbrooms came upon the scene just as New Jersey officials were beginning to despair of ever finding a practical fog-dispersal system for their highways. Giant fans installed several years ago along the New Jersey Turnpike to blow fog away instead seemed to draw more into the area. Propane jets, used successfully to clear fog around Paris' Orly Airport, would be prohibitively costly to install along miles of highway. Like silver-iodide seeding--another technique used to clear fog from airports--the Orly system is effective only against fogs that occur at below-freezing temperatures; most New Jersey fogs form at warmer temperatures. The propane jets also have a side effect that makes them even more impractical for highway use: they generate light snowfalls that have actually been blamed for a chain of auto collisions on a road in the vicinity of Orly.

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