BOISE (AP) — Idaho lawmakers are gearing up to spend the final few weeks of the legislative session focused on transportation funding, including a key tool the Legislature hasn’t leveraged since 2005.

Last week, Republican state Sen. Bert Brackett, of Rogerson, introduced legislation to allow the state to borrow $300 million in bonds for road projects. The bill is expected to be debated during a hearing Thursday before the Senate Transportation Committee. Here’s a primer on what you need to know:

WHAT KIND OF BOND IS THIS?

Known as “Grant Anticipation Revenue Bonds” — or GARVEE bonds — these bonds allow states to pay for new road projects and repay it with future federal highway payments. It’s a shift from a pay-as-you-go method because it allows states to fund critical transportation projects without putting up the cash first.

As of December 2016, 25 states and three territories have issued over $20.4 billion in GARVEEs, according to the U.S. Department of Transportation.

WHY DOES IDAHO NEED IT?

Idaho currently doesn’t funnel general tax dollars to pay for the state’s aging roads and bridges. Instead it relies on revenue from the gas tax and registration fees to cover the costs. This system hasn’t been enough to keep up with the state’s maintenance, repairs and construction needs, leaving the state with a $262 million a year transportation deficit. Republican lawmakers have already shot down an attempt to raise the gas tax earlier this legislative session. Using a GARVEE bond is one of the remaining options lawmakers have left before adjournment to boost Idaho’s transportation budget.

HAS IDAHO USED GARVEE BONDS BEFORE?

Yes. Idaho first used these bonds in 2005 as part of an ambitious proposal first pitched former Gov. Dirk Kempthorne. The plan originally allowed Idaho to borrow $1.6 billion to improve 258 miles identified in Idaho’s 13 most clogged and crumbling traffic corridors. That projected was eventually trimmed to just $857 million to add relief to six traffic corridors.

That project was eventually completed in 2015. Currently, Idaho still owes $564.2 million, which won’t be paid off until 2031.

WHAT DOES THIS NEW PROPOSAL DO?

Brackett’s proposal lists 12 out of the 13 corridors first identified in 2005 that would be funded with GARVEE bonds. These projects include building a new Snake River bridge in south-central Idaho and making improvements along U.S. 30 in eastern Idaho. However, all projects would require approval from the Legislature first.

The plan is expected to be heavily edited if it makes it over to the House, but Brackett said he will fight to carve out GARVEE funding before the anticipated March 24 adjournment.