PROVO — Like doctors giving a middle-age person a full physical exam, transportation officials have tried to gauge the health of Utah County's stretch of I-15. The diagnosis: fairly healthy considering age. The prognosis: clogged arteries and complete "system failure" in the next 30 years.

"That freeway was built in the '60s, and there's a lot of things that won't function with an increase in traffic," said Matthew Swapp, Utah Department of Transportation project manager.

UDOT and the Mountainland Association of Governments, which represents Utah County governments, have teamed up to conduct an 18-month study of I-15. The first phase of the study has been to determine the condition of I-15 and how Utah County will handle the estimated 100 percent boom in its 360,000 population over the next 30 years.

"You look at this as a physical," said association transportation engineer Chad Worthen. "Overall, you're in good health, but the cholesterol level is way up . . . sooner or later you're going to have a heart attack."

According to the Utah County I-15 Corridor Management Plan, Utah County's population boom will start at the north and slowly work its way southwest, showing that Utah County's more immediate transportation needs will be in the north. Without expanding I-15, traffic jams in Lehi and the Provo-Orem areas will balloon — eventually turning I-15 into a "parking lot," said Darrell Cook, Mountainland Association of Governments executive director.

The study measured accident rates, pavement conditions and the remaining lifespan of bridges and overpasses.

Worthen said of the 97 structures in Utah County, about 34 will need to be replaced within 10 years, including the Provo Center Street interchange, the north Lehi interchange and the north Springville interchange, which is scheduled for construction within the next few years.

Having inspected the condition of bridge pillars, girders and decks, Worthen said another 18 structures will need attention within 10 to 15 years, and 20 more within 15 to 20 years.

Officials have also combed through hundreds of police reports over the past three years to determine some of Utah County's accident "hot spots."

According to the study, accidents most frequently happen between just north of the Provo Center Street interchange and just south of University Avenue exchange. Other high accident areas are the highway lanes between Salem and Payson and the north border of Orem to Utah Valley State College.

UDOT spokesman Geoff Dupaix said the accident data will show where safety improvements need to be made when the highway is reconstructed.

The cure for Utah County's ailing highway, Dupaix said, is a complete reconstruction project, along with more than $1 billion to fund it. From lane expansions and the introduction of high-occupancy vehicle lanes, to commuter rail and maybe even light rail, transportation needs a shot in the arm.

"It needs to beef up, it needs to work out in order to deal with the oncoming growth," Dupaix said.

But persuading legislators, the guardians of the state's purse strings, to fork over $1 billion is going to be tough.

Cook said once the study is complete, in about July, Utah County will be able to show state leaders that Utah County is indeed facing a transportation crisis. Plans are already afoot for a campaign to introduce a quarter-cent sales tax initiative, similar to the one adopted by Weber, Davis and Salt Lake counties last year.

Dupaix said Utah County residents appear to support a push for transportation improvement.

According to a Dan Jones poll commissioned by the Mountainland Association of Governments, of 302 Utah County residents polled, 42 percent listed growth as the top issue in the county with "traffic/roads" as the second concern. Traffic congestion was listed as one of the top problems by 72 percent.

Although most residents felt safe on I-15 and were comfortable with current freeway congestion, 91 percent of respondents said they saw traffic becoming a "serious problem" in 10 years.

Swapp said the next step is to analyze the information and begin to formulate projects that will improve traffic. The association and UDOT plan to hold a series of public meetings in the spring to receive public opinions on the problem.

"Public input is an important part of the planning process," Swapp said. "We want to know what the people who use I-15 think — what works, what doesn't work and what would make things better."