Drivers who travel Interstate 95 or any other major Maine road might notice on some stretches that the little bars on their cellular phone start to disappear, one by one.

Like trees in the rearview mirror, the bars eventually are gone altogether, leaving the dreaded words “no service.”

Now, imagine leaving the Interstate and traveling on one of the state’s many back roads. The chance of losing service is even greater.

Frustrating? Ten years ago, using a cell phone in a car was a novelty. But now that mobile service is a ubiquitous part of American culture, consumers won’t accept the possibility of being cut off from a call.

Constant, uninterrupted coverage is the new goal.

“The biggest complaint we get [from the public] is lack of service,” Wayne Jortner, a lawyer with the Maine Public Advocate’s Office, said.

“There are huge gaps in coverage, and we’re in the process of compiling as much data as possible to find out where those gaps are,” he added.

To meet consumer demands and close those gaps, cell phone companies such as Unicel and U.S. Cellular are starting to expand their coverage areas farther into the rural reaches of Maine.

Other companies, such as Verizon, AT&T and T-Mobile, also are moving deeper into the state, giving Maine cell phone users myriad wireless options.

“The number of cell phones is starting to outnumber land lines, and cell phone companies are starting to be more aggressive in their packaging,” Maine Public Utilities Commission spokesman Phil Lindley said.

Even Gov. John Baldacci called for increased wireless coverage in his State of the State address. Baldacci’s ConnectMe proposal would ensure cell phone service in all of Maine’s communities by 2008.

A lofty goal, perhaps, but the infrastructure is primarily in place.

“We are looking to extend into thinly settled areas” of the state, said Kim Kenway, a lawyer who represents both U.S. Cellular and Unicel, Eastern Maine’s largest cellular phone companies, “if for no other reason than for public safety purposes.”

People like Jortner in the Public Advocate’s Office also have a commitment to meet consumer needs. But finding the gaps in coverage he spoke about has proven to be a problem because tracking the cell phone towers that transmit signals is nearly impossible.

Compounding the problem, cell phone companies are mum about their own tower locations for competition purposes, behavior Jortner said borders on paranoia.

“The companies are reluctant to give away information. … Everything is proprietary,” Jortner said. “Even with sharing of towers, they’re worried about competition.”

Sharing towers is a recent trend gaining momentum in the cell phone industry because it allows several companies to utilize the same space.

“A lot of towers are owned by independent tower companies, not cell phone companies,” Lindley said.

Independent companies can purchase a tower, rent the space to multiple companies, and reap the profits. Jortner said it’s a good way to keep the number of towers to a relative minimum.

Mesa Communications Group LLC, headquartered in Virginia, owns and leases tower space to cell phone companies all over the East Coast and is Maine’s largest cell phone tower proprietor.

The company has a network of 65 towers running from the southern tip of the state to the end of Interstate 95. Typically, the towers are about five miles apart.

“We try to concentrate in second- and third-tier markets. … Clearly all of Maine outside of Portland would qualify as that,” said Jack Rupert, vice president of acquisition and development for Mesa Communications.

“We have designed a network of towers that we feel will serve multiple carriers.”

Unlike cell phone carriers themselves, Mesa Communications has the luxury of putting competition aside, Rupert said. His company can serve – and collect money – from all of them.

“We’re dictated by what the carriers do,” he said. “Some have [begun] to branch out and use our network. They understand that it’s very expensive to roll out a network.”

Mesa Communications already has a network of towers in place, and it’s one that Rupert said is only going to keep growing. All of Maine’s towers owned by Mesa have more than one carrier.

“We don’t need everybody on board, but we can’t just justify renting to one,” Rupert said.

Mesa Communications has no concerns with revealing its tower locations, but cell phone companies remain guarded.

Technically, the companies have every right to be. Only towers 200 feet or taller – which are required by the Federal Aviation Administration to have safety lighting – are federally registered. That means the actual number of cell phone towers in Maine remains indeterminable.

Thousands of towers that are shorter than 200 feet – including nearly all of Mesa Communications’ towers – are controlled only by local zoning regulations and have popped up in droves during the boom of cell phones and pagers.

“We don’t regulate cell phones,” PUC representative Lindley said. “We don’t get accurate enough information about coverage, about numbers of customers or about where towers are.”

In fact, no state agency is responsible for regulating cell phone towers or coverage. The Federal Communications Commission is the national authority on everything wireless but doesn’t pay close attention to this quiet little corner of the country.

“Wireless service is regulated at the federal level and has been for a long time,” Lindley said. “Lately, though, the rules have become more open and more lax.”

For instance, rules that govern cell phone towers deal with zoning requirements and height restrictions, but a town can’t “arbitrarily say no to putting up a cell phone tower,” Lindley said.

Under the Federal Telecommunications Act of 1996, no municipality may have a blanket prohibition against cell towers. They must be allowed somewhere in town where installation is feasible.

Towns can resist only so much, and towers slowly are being accepted as consumers understand the importance of strong, continuous coverage. That’s where companies like Mesa Communications come in.

“I applaud the governor for his efforts to bring more attention to the need for [cell phone] service,” Rupert said. “The fact the he’s bringing attention to it will get the companies to look at the opportunity a little closer.”

With all these towers, and all this attention focused on cell phone coverage, how can there still be such large gaps? The answer, Rupert said, is business.

“The theory that some people have is, ‘If you build it, they will come,'” he explains, “but that’s not necessarily true.” Rupert emphasized that cell phone companies will extend only into areas where they will profit.