LITTLE ROCK, Ark. (AP) — The Arkansas Supreme Court on Thursday said a half-cent sales tax can’t be used to fund a $1 billion project widening an interstate corridor in the heart of downtown Little Rock.

Justices ruled that the sales tax, approved by voters in 2012, cannot be used for any highways with more than four lanes. The court reversed and remanded a Pulaski County judge’s decision to dismiss a lawsuit challenging the Interstate 30 corridor project running through downtown Little Rock and North Little Rock.

The project expands the 6.7-mile I-30 corridor from six to as many as 10 lanes in some portions.

Justices, however, noted that the constitutional amendment voters approved for the tax repeatedly refers to the money to be used for four-lane highways.

“The repeated reference to ‘four-lane highways’ and the lack of a specific reference to six-lane interstate highways means the Amendment 91 funds cannot be used for the latter,” the court said in its ruling.