Sm-o-o-o-th!

That's what the Pennsylvania Department of Transportation is saying about the reconstructed northbound lanes of Interstate 79 from the Ohio River to the I-279 junction in Franklin Park.

In announcing that the new lanes are to be opened to traffic today, PennDOT said the International Roughness Index of the 4.4-mile stretch has been placed at 27.5 inches per mile, the total amount of horizontal undulations or unevenness in the new asphalt pavement as determined by laser measuring.

As an analogy, PennDOT said IRI scores are like golf scores -- the lower, the better.

And by comparison, the next best IRI rating, at 30 inches per mile, is on I-90 through Erie County, making the rebuilt stretch of I-79 the smoothest in Pennsylvania.

"It's quite a distinction and credit to our project team to transform this section of interstate from worst to first in ride quality in the state," PennDOT District 11 Executive Dan Cessna said. "From end to end, I-79 northbound is a great ride in Allegheny County."

Before work began this spring, I-79 north of the Ohio River had an IRI of 228.5 inches per mile, not counting potholes that riddled the 30-year-old pavement, making for a bumpy ride for about 41,000 cars and 6,000 trucks traveling the highway on the average weekday.

PennDOT is spending $61 million to rebuild the road, pulverizing the old concrete and recycling it as a base for a 25.5-inch thick asphalt top. About 305,000 tons of asphalt are being used for four 12-foot-wide lanes, new shoulders and interchange ramps.

The southbound lanes will be done next year, when traffic restrictions similar to those during this construction season will be imposed.

Some traffic restrictions will continue during off-peak hours for the next few weeks while the contractor wraps up activities for winter.

The I-79 overpass at Mount Nebo Road/Exit 68 is to be fully reopened on Thursday.

In addition to providing new pavement, the project includes installing new drainage systems, guide rails, pavement markings, lights, signs, culverts and "intelligent transportation amenities" to monitor traffic and road conditions. Overpasses at Nicholson Road and Rochester Road also have been reconstructed.