HARTFORD, Conn. (AP) — Eighteen years, three governors and $567 million after a study was commissioned to come up with a way to improve public transportation in central Connecticut, a bus-only corridor is about to open, promising to overtake motorists sitting on traffic-clogged Interstate 84.Gov. Dannel P. Malloy, state Transportation Commissioner James Redeker and other state and federal transportation officials gathered Friday to mark the opening of CTfastrak. The bus-only corridor’s first full day of operation will be Saturday.State officials insist the 9.4-mile system between Hartford and New Britain will be a quick, reliable and environmentally friendly alternative to cars. Critics call it a boondoggle that’s taking money from other transportation projects.

___Q. How is the bus-only corridor different from other types of mass transit?A. CTfastrak, as the bus-only corridor is called, has been promoted by state officials as a fast and efficient alternative to cars and intercity buses. The buses will run on a dedicated course, unimpeded by cars and trucks. For motorists frustrated by traffic jams caused by jackknifed trucks, a route free of other traffic is welcome. Touted as a bus rapid transit system, CTfastrak promises waiting times of less than 10 minutes during peak periods.State officials project more than 16,000 daily riders in 2030, double the number of bus passengers in the corridor now. Michael Sanders, the Transportation Department’s transit administrator, is confident CTfastrakwill draw in riders from universities and crowds from special events.Therese W. McMillan, acting administrator of the Federal Transit Administration, said bus rapid transits elsewhere in the U.S. — Cleveland, Pittsburgh and Grand Rapids, Michigan — are “attracting a real following.”Geoff Slater, a principal at Nelson(backslash)Nygaard Consulting Associates Inc. in Boston, said the busway will have an advantage over buses that stop and go through neighborhoods. “They’re going to be fast and very convenient,” he said.___Q. Why has it drawn opposition?A. In a word: cost. The nearly half-billion-dollar price tag — $112 million in state money and the rest from the federal government — has been heavily criticized. Although the project’s planning began long before Malloy took office in January 2011, he announced his backing three months later because he said he was reluctant to refuse federal money and risk future funding from Washington.State Sen. Joe Markley, a Southington Republican, has been among the fiercest critics. “Having put nearly $600 million into it I can only hope it works out,” he said. Still, he criticized spending so much money on a new project “when we have crumbling infrastructure.”Malloy criticized opponents in 2011 for saying the project might delay or prevent “additional commitments” to transportation in Connecticut.“I can assure you this project stands on its own merits,” he said.___Q. What do backers say are the transportation benefits of the bus-only corridor?A. State transportation officials say it’s more flexible than rail because buses can exit the corridor and continue to other destinations. The CTfastrak guideway will be two lanes with bus pullouts for drop-offs and pickups and for express buses to pass without being delayed.The state also says the system is environmentally friendly. The buses are diesel-electric hybrids that transportation officials say will help improve air quality.___Q. What do supporters say are the economic development benefits?A. The busway is intended to boost Connecticut’s economy by spurring commercial and residential growth along the route. By that standard, it’s already a success, Redeker said. Private investment for building housing near bus route stops and an industrial site cleanup in Newington have already begun, he said.“I would declare it a success before we open it,” he said.Steven Schiller, a planner for the city of New Britain, said inquiries have already been made about available properties along the bus-only corridor. “It’s starting to be looked at,” he said.City officials are initially seeking grant money to spruce up downtown and change zoning to attract development, Schiller said.___Follow Stephen Singer on Twitter at https://twitter.com/SteveSinger10