"If you build it they will come" is a statement that is both true and incomplete when it comes to new highways and mass-transit systems in Utah, say transportation planners.

"If we build it they will come. And if we don't build it, they'll come anyway," said Wasatch Front Regional Council spokesman Sam Klemm.

Utah's population is growing; by one estimate, Salt Lake County's 930,000 people will increase to 1.4 million by the year 2040 — whether or not transportation and mass-transit infrastructure commensurately increase.

The only difference, transportation planners say, will be whether all those people will be sitting in traffic swearing at each other or cheerily zipping along in light-rail cars and HOV lanes.

"Transportation systems accommodate population — they don't create population," said Darrell Cook, Mountainland Association of Governments executive director Cook, Klemm, Wasatch Front Regional Council executive director Chuck Chappell and West Valley Mayor Dennis Nordfelt met with the Deseret Morning News editorial board Monday as part of a coordinated effort to gain support for increased taxes and other funding sources for new transportation infrastructure.

According to a new brochure jointly issued by Mountainland and the WFRC, there is a funding gap of $5.5 billion in critical transportation needs over the next 10 years, $4 billion of that in highways.

"We feel like we're before the firing squad," Cook said. "We are in such desperate need with our roads."

For example, Cook said that in 10 years the Utah County I-15 Alpine/Highland interchange is projected to have a 2 1/2-mile backup during peak hours if it remains in its present state. Hundreds of similar scenarios exist all over the Wasatch Front.

A bill dubbed the Transportation Investment Act is making its way through the Legislature this session that, if successful, would take a part of the state's $270 million to $300 million in annual sales taxes related to automobiles (sales, parts, service) to use for transportation funding.

That would close about half the highway funding gap. For the other half, transportation planners are proposing a variety of schemes including regional gasoline taxes (in addition to the already existing federal and state taxes), impact fees, increased vehicle registration fees, statewide property taxes and others.

Admittedly, "the alternatives in the near term are very tough," Cook said. "When you begin, you look outside of the box and give it your best shot."

The Wasatch Front Regional Council and similar pro-highway organizations have come under considerable criticism from pro-mass-transit types — most visibly Salt Lake City Mayor Rocky Anderson — but Chappell said he's being realistic.