sentences:  The interchange with MD 68 and MD 63 south of Williamsport originally only had a northbound exit ramp and a southbound entrance ramp; ramps to and from the direction of Hagerstown were added between 1981 and 1989.The junction with Halfway Boulevard was a diamond interchange until it was rebuilt as a partial cloverleaf interchange in 2001.I-81 is heavily congested within Maryland due to the 1960s era freeway being used as both a commuter route within a rapidly growing metropolitan area as well as a major trucking corridor.