Bombarded by Billboards. Some cities are moving to ban outdoor ads, while the industry quietly works to expand. ADVERTISING: YOU CAN'T AVOID

AS advertising, billboards have an undeniable advantage. You can flip over a magazine page, and turn off the TV. But a billboard is there whether you like it or not. ``Try turning your eyes from that ad, and you wreck your car,'' says Edward McMahon, who heads an organization called Scenic America (formerly Coalition for Scenic Beauty), pointing to a billboard on a highway curve.

The very quality that makes billboards attractive to advertisers - the way they dominate public spaces - makes them annoying to many others. Numerous cities - among them St. Louis, Houston, and San Francisco - are moving to curb outdoor ads. Maine and Vermont have joined Hawaii and Alaska in banning them entirely.

A spate of local newspaper stories, moreover, has exposed such matters as the strange absence of billboards from local property tax rolls (or the low valuations reported) and the way billboards are saturating minority neighborhoods with glamorous portrayals of cigarettes and booze.

Leading the charge is Mr. McMahon, who calls the industry an ``organized lobby on behalf of ugliness in America.''

``A fight for survival,'' is how Signs of the Times, a trade publication, describes the challenge facing the industry.

The billboard wars are hardly new. Many supposed that Congress had declared a permanent truce when it passed Lady Bird Johnson's Highway Beautification Act in 1965. Billboard companies think so. ``The act has been a success,'' says Myron Laible of the Outdoor Advertising Association of America (OAAA). ``Over 90 percent of the illegal signs in America have been removed.''

To McMahon, that simply shows how weak the law turned out to be. He says it is so full of loopholes, and enforcement has been so lax, that there are as many billboards on the nation's highways today as there were 20 years ago. Four new billboards are going up for every one that comes down, he says. And these new ads are bigger, perched on metal poles that can climb 50 feet into the air. McMahon cites a 1984 report from the federal Department of Transportation concluding that the Beautification Act ``has not effectively improved or protected the aesthetic quality of the federal highways.''

A former law professor at Georgetown University, McMahon is something of an oddity in Washington environmental circles: an Alabamian who talks Deep South with a rambunctious good humor. Two years in the service, in Europe, convinced him that America was losing its local character and identity. ``I saw the homogenization of the American landscape,'' he recalled in a recent interview.

``We are saving the doughnut holes of pristine places but losing the doughnut,'' he says. Pretty soon, you are ``going to have to go to Disney World to find something individual and unique.''

In Scenic America's renovated offices about seven blocks from the Capitol, McMahon shows a visitor a slide show he assembled on his travels. It is not the kind tourist bureaus would provide.

He shows highway landscapes - planted with taxpayer money - denuded for the benefit of billboards. There's the schizophrenic: a double billboard in Houston advertising treatment for alcoholics on the bottom and liquor on the top. And the truly macabre, a billboard in a cemetery touting Salem cigarettes.

A single street corner in Baltimore has seven billboards - three for cigarettes and three for liquor.

``They put billboards next to churches and elementary schools,'' McMahon says. ``They will put an ad anywhere and everywhere they can.''

McMahon's twangy fervor is hard to resist. Not long ago he spoke before a conservative business group in Houston. ``He had people practically standing up and cheering,'' says Peter Brown, an architect who heads an anti-billboard group there.

McMahon gets especially outraged at loopholes in the federal billboard law. For example, localities have to pay cash compensation for billboards ordered taken down. That sounds reasonable enough. But courts had long permitted an alternative: Let the signs stay up long enough for the owners to get back their investment.

The cash-up-front law means fewer billboards come down, since cash is something most localities don't have. (Federal funding has just about dried up.) Besides, McMahon says, billboards have value in the first place only because they sit next to highways that taxpayers pay for. ``We are paying to bring the customer to the billboards,'' McMahon says.

The billboard industry is relatively small, unable to muster the kind of grass-roots political army that, say, real estate agents can. The industry compensates by targeting its money to key committee chairmen. McMahon's research shows it ranks right behind the defense and tobacco industries as a provider of ``honorariums'' - payments to congressmen for appearing at industry events.

McMahon got hold of an industry memo outlining lobbying strategies at the local level. In one, the mayor gets free use of billboards to promote local charities. Public-service ads, he notes, tend to sprout when localities consider anti-billboard laws.

``Their strength lies in political control,'' says Peter Davis, a Wilmington, N.C., businessman who led an anti-billboard campaign there. ``They have no public support.''

That political strength is facing a new force, however: local business leaders worried that a tacky ambiance will drive away new investment. ``I'm a businessman asking for controls on business,'' Mr. Davis says.

``Ugly ain't good for business,'' adds Peter Wiley of the Central Philadelphia Development Corporation, which lobbied hard for new billboard restrictions there.

Billboard representatives contend they are taking the blame for commercial clutter generally. Store signs, they say, can be just as bad as billboards. Mr. Laible of the OAAA argues that alcohol and tobacco ads have dropped by 50 percent over the last five years.

The Beautification Act wasn't supposed to prohibit billboards altogether, he says. Rather, it was supposed to restrict them to ``business areas where other businesses belong.''

On this much, at least, the two sides agree. ``Outdoor advertising may have its place,'' McMahon says. ``That place is not everywhere.''