DENVER -- State transportation officials are considering charging all drivers passing through the Eisenhower Tunnel up to $3 to help ease congestion on Interstate 70.

The proposed toll would help pay for a third bore of lanes through the Continental Divide. A toll at the tunnel in Idaho Springs is also being considered.

Officials first thought they could just charge a toll for drivers using the new lanes but then realized that wouldn't raise enough money.

The tunnel toll was one of several proposed Thursday by the Colorado Tolling Enterprise. It was set up two years ago by the legislature to help the cash-strapped state solve its transportation problems.

The other proposals involve charging drivers on new lanes to be built in metro Denver and Colorado Springs.

All the proposals still require further study, said Peggy Catlin, acting director of the toll authority.

Current law only allows tolls to be charged on new roads so transportation officials would have to convince lawmakers to change the law to allow a toll at the Eisenhower Tunnel.

Idaho Springs mayor Dennis Lunbery said residents and businesses along I-70 worry about widening the highway since their towns are so close to the highway already.

"We don't think being able to toll all the lanes is a good idea. We believe a transit solution is the best way to go," he said.

The Colorado Department of Transportation estimates it will need an extra $100 billion to meet the state's highway needs over the next 25 years.

It could take 20 years to build all the proposed roads but some toll lanes could open as early as 2010, said Tom Norton, the department's executive director.

Bonds would be sold to pay for construction and toll revenue would pay of that debt.

"By leveraging toll revenue, we would be able to build $3 billion of increased highway capacity and transportation infrastructure," said Catlin. "Toll revenues would cover the majority of those costs with only $300 million of that investment being federal, state or local dollars. With tolling, we can address the transportation needs of these corridors in the next several years. Without tolling, projected revenue for transportation indicates that only spot improvements will be made on a few of the corridors over the next 25 years, but none will undergo a major upgrade like we're doing on the T-REX project."

Other potential toll roads considered were:

I-25 North: Construction of two new reversible express toll lanes from US 36 to 120th Avenue connecting to four new express toll lanes extending to SH 66.
I-70 East: Construction of four new express toll lanes from Colorado Boulevard to Chambers.
US 36 : Construction of four new express toll lanes from I-25 to McCaslin and two new express toll lanes to Cherryvale.
I-225: Construction of four new express toll lanes from I-70 to Parker Road.
I-270: Construction of four new express toll lanes from I-25 to I-70.
C-470: Construction of four new express toll lanes from I-70 to I-25.
Northwest Corridor: New toll road construction in the northwest segment of the city.
Powers Boulevard in El Paso County: Construction of new tolled connections to I-25 from existing Powers Boulevard on the north and south end of the roadway. The middle section of Powers would remain toll free pending its upgrade to a limited-access freeway.