A growing Las Vegas Valley population and increasingly congested roads means a light rail or express bus line can expect to have more than 80,000 daily riders within 25 years, a consultant told a light rail steering committee Thursday.

But critics of a proposed Henderson-to-North Las Vegas rapid transit system expressed skepticism over that figure, along with cost projections for such a system.

"It's a guess," said Wendy Lee Meoz, a member of the Regional Transportation Commission-appointed committee and a rapid transit critic.

Not so, said Phil Hoffman, representing commission-hired consultant Parsons Transportation Group: "It's a heck of a lot better than a guess."

Hoffman said regional studies predict a 90 percent increase in valley population by 2030, but only a 32 percent increase in new highway lanes in that time, spurring demand for transit alternatives.

Meeting increased demand for new roads in that time could cost $10 billion, in addition to $4 billion needed for road projects already on deck in the next 25 years, Hoffman said.

The proposed rapid transit line -- called a regional fixed guideway -- at first would ply a 33-mile route from near Nevada State College in Henderson along existing Union Pacific Railroad tracks to Frank Sinatra Drive.

From there, the line would run northeast along Fifth Street, Centennial Parkway and Pecos Road to a North Las Vegas terminal.

If financing is obtained, construction could start as soon as 2010, with an opening no sooner than 2014.

Creating a light rail line along that route would cost $713 million to build and $70 million a year to operate. The construction cost of about $20 million per mile is on the low end of what such systems typically cost.

"This primarily operates at grade. You don't have many bridges," Hoffman said. "That's what adds a tremendous amount of cost."

Building an express bus line using bus-only lanes would cost $613 million to build and another $85 million a year to operate, Hoffman said.

Hoffman said ridership estimates are conservative.

"Generally, the actual ridership after the actual system is built is higher than what was forecast," he said.

But critics noted ridership levels on the Las Vegas Monorail that are barely over half of what was first predicted and expressed skepticism that costs would stay in line.

"Projections are always 50 (percent) to 100 percent under costs when it comes to government projects," Jeff Belcher, a Henderson resident, told the committee. "Rider projections are always overly optimistic."

Ingrid Reisman, a commission spokeswoman, disagreed, noting that Citizens Area Transit bus ridership has nearly quadrupled in the past decade or so.

"The demand is there. There's going to be an increase in population. We know that," Reisman said after the meeting.

Creating an express bus line using existing streets would cost $94 million to build and $50 million a year to run, but would draw less than 39,000 passengers daily, Hoffman said.

North Las Vegas is expected to be the starting point for roughly two-thirds of riders, with the rest starting from Henderson. Seven out of 10 riders are predicted to be locals, Hoffman said.

"The Henderson area is a fairly affluent area. Those results don't surprise us," Hoffman said. "We suspect there may be a little lower ridership in Henderson than North Las Vegas."

The committee is expected to make a nonbinding recommendation on how to proceed at its Jan. 19 meeting. That suggestion will then go to the full commission, which is empowered to make a binding decision.

One option that the commission can consider, but won't be offered by the committee, is doing nothing.

The committee voted 10-9 to ignore a no-build option, much to the consternation of critics.

"It really gives a flavor of impropriety to eliminate one of the options, when we're so close to the end of the process,' said Beverly Dix, a committee member and rail critic.

Dix said she's pushing the committee to suggest a referendum on the project, which has drawn vocal opposition from some homeowners living along tracks in Henderson.