ST. IGNACE, MI -- At long last, drivers crossing the Mackinac Bridge can pay the toll using a credit card without having to park and pay inside the bridge office.

The Mackinac Bridge Authority says that credit card payment was finally deployed in the lanes just prior to Memorial Day weekend; the culmination of a long-stalled technology upgrade the state signed the initial contract for five years ago.

"We're thrilled," said James Lake, Michigan Department of Transportation spokesperson. "It's been a long time coming."

In 2015, the bridge authority announced it would begin accepting credit card payment in the lane that year, but technical glitches, stalled contract negotiations and a long unexplained absence of a subcontractor seriously delayed the project.

The upgrade at Mackinac was part of a seven-year, $6.9 million contract with Xerox that included a coordinated software update at the International Bridge in Sault Ste. Marie and the Blue Water Bridge in Port Huron as well.

Software upgrades will follow in the Soo and Port Huron, although the International Bridge elected not to pursue credit card processing in the lanes.

Before last month, drivers without cash had to park and pay the $2 per axle toll with a credit card in the Mackinac Bridge Authority office.

The Mackinac Bridge is processing credit card transactions using a Xerox Vector 4G system, which includes financial security checks that take a couple more seconds per transaction for verification on top of the current average of 12 seconds per car.

Lake said the bridge may restrict the number of lanes where drivers can swipe a card during heavy traffic volumes to avoid backups. The bridge tries to keep average stop stops for toll payment under 11 to 12 seconds to avoid backups during peak traffic times. The toll plaza has 10 lanes but typically only 8 are in regular use.

More than 2,200 drivers swiped a credit card on Memorial Day weekend. Electronic bridge signs direct drivers to which lanes take plastic. Lake said about 0.5 percent of drivers have paid with plastic since the new availability, although "we expect that to grow as more customers are aware of the option."

Bob Sweeney, executive secretary at the bridge authority, said testing has reached a point where the bridge is "comfortable that it is operating reliably and securely."

"We're happy this new feature is available for our customers, and we're sure they'll appreciate the additional convenience and option is offers," he said.