RALEIGH As budget cuts and prison closings shrink the inmate labor available to pick up trash along North Carolina highways, the state Department of Transportation is trying to fill the gap with business sponsors who pay for litter removal by the mile.

Blue signs have sprouted along Interstate 40 in Durham and Wake counties this year to promote the first handful of recruits to North Carolina’s Sponsor-A-Highway program. They range from the Angus Barn restaurant and other local stalwarts to Mixed Chicks, a national line of hair-care products.

Prices vary, but most sponsors paid $650 up front for a sign with the company logo, plus $300 a month to have litter picked up about every four weeks along one sponsored mile of the highway shoulder.

“This is about being involved in our community and supporting the people that shop with us,” said Michelle Mitchell, marketing manager for Garner-based Agri Supply Co., which has eight home-and-farm supply stores in three states. Agri Supply sponsors litter removal on a mile of I-40 near Garner, and on a mile of I-95 near its store in Lumberton.

“We’re spending our money in the areas where our customers are, and getting our name out there,” Mitchell said. “We’ve had a couple of customers who come in the store and mention the signs.”

DOT doesn’t spend state money for Sponsor-A-Highway, and it stays out of the transaction altogether. Each sponsor works with one of two California firms with similar names that are authorized by DOT to take the money, erect the sponsorship sign, and make sure the trash is picked up at least 13 times a year.

“We provide the litter removal, and they get the recognition,” said Melinda Centner, CEO of Adopt A Highway Litter Removal Service of America ( www.adoptahighway.net), based in Encinitas, Calif. The other company is Adopt A Highway Maintenance Corp. ( www.adoptahighway.com) of Santa Ana, Calif.

The two companies began soliciting sponsors last December for cleanup on Interstate 40 between Chapel Hill and Wilmington, and on the entire length of I-95. They’ve made a modest start with nine sponsors so far for 14 one-mile segments, mostly in western Wake County.

“Well, it’s early. I would like to see a lot more,” said George Kapetanakis, who runs the DOT roadside beautification program. “I have two more sponsors in the hopper now, for two more segments.”

Sponsor-A-Highway uses paid workers, but North Carolina still relies mostly on free labor to pick up the soda bottles and old tires that drivers dump along our roadways.

The state collected 7.5 million pounds of trash last year. More than 4,600 civic groups and other volunteer squads in North Carolina’s Adopt-A-Highway program bagged 3.4 million pounds along 12,000 roadside miles. Another 2.3 million pounds was collected by minor criminal offenders sentenced to community service.

Prisoners also made a huge contribution in the past, but their role is declining. Inmates collected 878,000 pounds of litter in 2011, barely half their contribution two years earlier.

Recent prison closings in Durham and two other counties have cut the labor available for trash cleanup in several areas. And the legislature recently trimmed DOT’s inmate spending to $9.4 million a year – down from $11.2 million a few years ago.

Prisoners receive just 70 cents a day for their labor, but the DOT money also pays and equips prison guards, and covers other costs. The bill from the Department of Public Safety works out to about $95,000 a year for each squad of eight medium-custody inmates, who are supervised by two armed guards – and $49,000 for a crew of eight minimum-custody inmates, with one guard apiece.

There were 189 inmate crews working the roads in 2009 but only 125 this year.

This year DOT is inviting its two California partners to expand their Sponsor-A-Highway efforts in North Carolina. They’ll look for businesses that want to put their names on blue signs along interstates and U.S. highways in 10 northern Piedmont counties, including Orange County.

As long as drivers keep tossing their trash, Kapetanakis said, North Carolina will need help to clean up the messes they leave behind. He said he hopes the new program will attract plenty of sponsors.

“When I see those folks that are willing to pay to keep the road safe, keep the environment clean, I think of it as stewardship,” Kapetanakis said. “I want to do everything I can to make sure it works.”