AUGUSTA, Maine — They won’t be pulled over by Maine State Police troopers or written up anytime soon, but the mobile billboards or advertising trucks appearing sporadically on Maine roads and parking lots are violating state law, according to the Maine Department of Transportation.

“I’m just finding this out myself only because no one’s ever asked, but yes, they’re definitely illegal by statute because, by definition, they are not carriers,” said MDOT spokesman Ted Talbot. “According to Title 23 of Maine state law, those types of trucks are illegal by statute because they’re not carrying anything other than the sign or billboard.”

A “carrier” is defined as any vehicle — such as a bus, taxi, 18-wheel transport or panel truck — that transports people, products or materials.

“The reason buses can get away with that wrap advertising you see all over the entire bus is buses are carriers,” said Talbot. “These billboard trucks aren’t and apparently that puts them in violation.”

According to the statute, “signs located on or in the rolling stock of common carriers, except those which are determined by the commissioner to be circumventing the intent of this chapter,” are allowed.

So the public buses with the advertising “wraps” around the whole bus that contain advertising and promotional material for a company such as U.S. Cellular are allowed. But billboard trucks are not allowed in Maine.

A spokesman for U.S. Cellular had only a short comment when asked about the extent of the company’s use of billboard trucks and how the law would affect them.

“We are currently looking into the matter,” said Kelly Harfoot, U.S. Cellular communications manager.

The trucks have been around for a year or two, according to Talbot. Since they serve no purpose other than advertisement, they violate the billboard statute.

“The spirit of the law might not be violated, per se, but it’s technically still a violation,” Talbot said.

So what to do the next time a billboard truck is seen rolling down the highway?

“We first have to catch up to the companies and let them know this is in violation of Maine law,” Talbot explained. “They will all be notified that the use of these trucks isn’t permitted in Maine.”

Talbot said he’s unaware of any complaints his department has received from people about the billboard trucks, although a BDN reader emailed the paper late last month, saying he had talked to an MDOT official and was told they did indeed violate the law.

“We will not enforce the law on those carrying out commerce initially,” Talbot said. “We never want to get in the way of commerce, ever, but it is a violation that would involve punishment for repeated violations.”

The first law banning billboards in Maine was enacted in 1977, according to Richard Hewes, an MDOT lawyer.

“And what followed was a whole slew of amendments and revisions,” said Hewes. “Billboard laws have been around in various forms since the 1930s, but this law sought statewide removal of all billboards in Maine.”

Hewes said the law was challenged in a lawsuit, which wound up in the Maine Supreme Judicial Court in 1982. The court upheld the ban.