Bicyclists are afraid of the dark, and with good reason. Riding at night, statistics show, is many times more dangerous than pedaling by day, simply because motorists often don't see cyclists at night--even when they carry reflectors and little bike lights. An Arlington bike commuter, lawyer and nationally known traffic safety expert decided in 1975 that he would build a really bright bike light system so bikers could both see and be seen. Ed Kearney has since sold about 1,000 of his rechargeable battery lights, which he advertises as "the best bicycle lights in the world." In a 1978 review of bike lights, Bicycling Magazine agreed. His new halogen lights put out five times the light of the best generator lights, even those equipped with halogen lamps, says Kearney. At five to eight pounds and $75 to $150, with a rat's nest of wires and a battery that must be recharged almost every night, Kearney's lights may not appeal to everyone. Certainly his (optional) huge rear flashing yellow "barricade" light is not sleek. However, it certainly gets motorists' attention. Bike helmets are ugly and clumsy too--but they save lives. For the serious cyclist who wants a really good, bright system, the Kearney lights are it. Where else can you call up the manufacturer at home if you have a question, or just want to chat? CAPTION: Picture, Bicycle lights. $75 for headlight and rechargeable battery unit, up to $150 for head and tail lights, flashing amber rear light, all accessories. Towpath Cycle, 1667 Wisconsin Ave. NW. 337-7356. And other bicycle shops. Or order from Ed Kearney Bicycle Lighting Systems, Box 1457, Falls Church 22041. 941-0666.