Louisiana has refinanced $649 million in highway project borrowing to take advantage of lower interest rates.

Treasurer John Kennedy’s office said Friday that the refinancing, done this week, will save the state $109 million over 26 years in lessened interest payments on the debt.

Under state law, the savings can only be used to pay for a list of transportation projects that were financed by the bonds, according to the treasurer’s office.

The state sells bonds to investors for upfront cash to pay for construction projects, then pays off the debt over decades with interest.

With this week’s refinancing, the new interest rate for the highway project bonds falls below 3.7 percent. It had been 4.7 percent.