PITTSBURGH — A new Pittsburgh Marathon route that crosses all three of the city’s rivers provides enough room this year for a projected record number of 18,000 runners — and thousands more if the race continues to grow, organizers said at a news conference Wednesday.

The route change is one of several made to grow the race that resumed in 2009 after a five-year hiatus prompted by police overtime and other costs that caused city’s support to dwindle and, in turn, discouraged sponsors.

The race was run from 1985 to 2003 when it drew up to 6,000 participants from all 50 states and 20 countries. This year’s race is May 15 and is again sponsored by Dick’s Sporting Goods, a national chain based in nearby Findlay Township.

Last year’s race attracted a record 16,000 runners, including participants in a half-marathon and several hundred relay teams. The new route crossing the Allegheny, Monongahela and Ohio rivers was chosen to accommodate 2,000 more runners expected this year, but would be safe for up to 35,000, race director Patrice Matamoros said.

Two of the key changes are roomier starting and finish line areas.

The race will start at Sixth and Liberty avenues, affording runners more than 2 miles of straightaway on the city’s widest undivided downtown street. The location will provide extra room for runners to back up all the way to Point State Park at the confluence of the three rivers before the race starts, and the long straightaway should safely thin the herd of runners as they start the race.

“It’s perfect because it does allow your front-runners to get out front,” Matamoros said.

The finish line is near Heinz Field on the city’s North Shore, an area containing several large parking lots that will provide a safe haven for finishing runners and race spectators.

Half-marathon runners will use the same start and finish lines because they’ll split off from the main race a little before the halfway point and dash across downtown to the North Shore.

USA Track & Field has sanctioned the new marathon route, meaning runners can qualify for the U.S. Olympic trials or the Boston Marathon if they run a fast enough time in their respective age groups, Matamoros said.

Mayor Luke Ravenstahl said the race’s rebound has been great for the city. He and Matamoros touted a marketing survey that showed runners, spectators and others pump $30 million into the local economy. The survey asked last year’s participants how much they spent because of the race and how well they liked it.

“Every year our regional economy has seen a significant boost” from the event, Ravenstahl said.

Ninety-seven percent of the runners said they’d recommend the race to friends and 88 percent of nonlocal runners said they would likely return to the city as tourists as a result of their experience, Matamoros said.