COLUMBIA, S.C. - Construction crews have opened all six lanes of Interstate 20 east of Columbia after a widening project that was finished more than a year ahead of schedule.

The South Carolina Department of Transportation said the new lane in each direction opened Sunday. Crews started the project to widen 6 miles of the freeway east on Interstate 77 in the fall of 2012.

The DOT used an innovative technique of splitting the lanes going in one direction to cut the time needed to finish the project from three years to 21 months.

The project isn't entirely finished. Transportation officials say they need to grind down the road, finish guardrails and take down a temporary barrier. That work will continue this summer.