According to Matt Laipple, PE, civil engineer with the public works department in Overland Park, Kan., his young community is lucky. City officials and staff have always understood that pavement preservation is necessary to keep road quality high and life-cycle costs low, and have been using pavement preservation techniques for the past 50 years.

“Many communities use mill-and-overlay — removing the top 2 inches of asphalt — on a 10- to 15-year cycle to provide a new wearing surface on asphalt pavement,” he says. “We can preserve nearly five times more lane-miles of pavement with micro surfacing or chip seal for the same cost. Other maintenance treatments may extend that figure further.”

Laipple says the goal of using pavement preservation techniques rather than wholesale mill and overlay (or mill-and-fill) is to keep the pavement's life-cycle cost low while maintaining serviceability and user satisfaction. Without some form of preventive maintenance program, it's not uncommon for an asphalt pavement to need complete reconstruction after 20 to 30 years.

While a regular mill-and-fill program will extend pavement life just as well as a preventive maintenance program, the life-cycle cost between the two approaches is dramatically different. Using recent local pricing and discounting future activity costs to present value with a 4% discount rate, the difference is $400,000 to $500,000 per mile of two-lane street over a 50-year period. That may not seem like a lot over 50 years, but multiply it by the number of miles in an agency's street network, and it adds up to serious dollars,” Laipple adds.