According to state Transportation Secretary Bradley L. Mallory, PennDOT uses a worldwide standard for measuring pavement smoothness called the International Roughness Index (IRI). The index measures pavement roughness in terms of the number of inches per mile that a laser, mounted in a specialized van, jumps as it is driven across the interstate and expressway system. The lower the IRI number, the smoother the ride.
Pennsylvania's 1999 interstate International Roughness Index median value was 88, surpassing the 1998 national standard of 92. Mallory attributed Pennsylvania's smoother roads to the nearly $6 billion that Gov. Ridge has invested in road construction and improvements over the last three years.
Mallory said PennDOT has scheduled rehabilitation work for the remaining interstates that are in poor condition within the next five years. PennDOT has adopted new smoothness specifications on future interstate construction projects that are among the most stringent in the nation, heightening its emphasis on smooth roads.
"It's only a matter of time before Pennsylvania's roads are among the smoothest in the nation," Mallory said.