It’s sort of like digging through the couch cushions for change — except the Utah Department of Transportation just found $451 million doing it.

The agency scoured accounts in recent highway projects for any unused money as construction closed out, or for savings on new work that is costing less than long-term budgets had set aside.

It found, for example, that a new project to extend the Mountain View Corridor from 4100 South to State Road 201 is costing $140 million less, from unexpected savings from moving utilities that reduced lawsuit risk. It saved $17 million on an Interstate 15 project in Davis County, and $15 million on another ongoing I-15 rebuilding project in Lehi.

Those were the biggest savings that officials found in 21 separate highway projects statewide — providing sort of a Christmas gift in spring to the Utah Transportation Commission.

After a month of study on where to spend that found money, it approved Friday speeding up or upgrading several long-planned projects — including converting U.S. 89 in Davis County into a full freeway; adding lanes to the planned West Davis Corridor highway; and building a long desired bridge over congestion-causing railroad tracks on 5600 West in Salt Lake City.

Following is a list of projects that will benefit:

• U.S. 89 in Farmington. The commission added $200 million to an earlier $275 million estimated cost to convert it into a full freeway between I-15 in Farmington to Interstate 84 at the mouth of Weber County.

UDOT says that as it recently completed environmental work on that project with community involvement, it realized it would cost far more than anticipated because the freeway could not simply use the highway’s current alignment.

For example, it will now provide a full frontage road along the entire route, costing $24 million. It will add 5 miles of noise walls, costing $14 million. It is adding a new bridge at Nicholls Road, costing $15 million. And it will require more extensive road shifts at interchanges than originally expected.

Transportation Commission member Jim Evans said it should help reduce congestion on nearby I-15.

• West Davis Highway. The commission added $190.75 million to the $609.25 million originally provided through bonding for the project.

UDOT said it found the bonds could not fund the original scope of the project — so it initially had decided to build only one lane in each direction in the northern four-mile end of the project. The new money will now allow two lanes in each direction for highway’s entire length.

“This will be a great asset for these communities,” said Transportation Commission Chairman Naghi Zeenati. Commissioner Dannie McConkie added that “it is a long time coming,” about 55 years.

• 5600 West in Salt Lake City. While the road has become a major north-south route for commuters, trains at a crossing near 700 South can back up vehicle traffic for long periods. The commission approved spending $3.35 million there to add a bridge. Union Pacific also is contributing to the project.

It will be on top of an $83 million project to widen 5600 West in the area from two to five lanes, improve intersections and convert its Interstate 80 interchange into a “diverging diamond” — where the two directions of traffic on 5600 West will cross to the opposite side of the freeway bridge to eliminate signal time needed for left turns.

• Porter Rockwell Boulevard in Bluffdale. As part of a project to extend that road — and make it a major artery — between Mountain View Corridor and Bangerter Highway/I-15, the commission is adding $17 million to build a long-planned bridge over the Jordan River and help construct roadway approaches to it.

• Interstate 15 statewide. The commission funded a new $1 million study to review existing plans and future needs for I-15 from border to border. It will look at capacity, operation and maintenance needs and create an implementation plan — with projected costs and timeframes.

• New I-15 Springville/Spanish Fork interchange. The commission funded $25 million to add ramps to the existing bridge at 1600 South in Springville (named 2700 North on the Spanish Fork side of the freeway) to create an interchange. It will also add improvements to cross streets.

• Heber City bypass. The commission approved $4 million for an environmental study needed for the proposed Heber Valley Parkway that could allow U.S. 40 traffic to avoid congestion in downtown Heber City. It could choose an alignment to allow officials to preserve a corridor for future construction.

• State Road 30 in Cache County. The commission is adding $10 million to projects to help widen the road that is considered a back door out of Cache Valley to the Wasatch Front.