To help manage its 3200 two-lane miles of highways, the Vermont Agency of Transportation uses a pavement management system from Deighton Associates Ltd. of Bowmanville, Ontario.
“If we didn't have Deighton, it would be a crapshoot as to how much hot-mix asphalt to put down,” says Mike Pologruto, Vermont's paving program manager.
The software's lifecycle cost capability allows the agency to quantify how long a treatment will perform at any given level. While any treatment may bump up the condition of a road to “very good,” the software calculates the cost of the treatment over the road's life.
For example, it might cost $2 million to put down a simple 2-inch-thick asphalt overlay that will last eight years. Another option would be to mill out 2 inches of old asphalt and replace it with 2 inches of new hot-mix. While the latter option would cost more than $2 million, it would last 15 years, resulting in a lower lifecycle cost.
After studying the state's highway network via the pavement management system, Pologruto and his team realized that different roads react differently to different rehab techniques. The department uses that information to determine the most cost-effective option for a particular stretch of road.
The interstate highway, for example, has an engineered, well-drained base structure. By contrast, an aging state road might have a poorly drained base of silt and sand that will heave and dip as a result of moisture and frost.
“A 2-inch overlay will perform better for far longer on the interstate than on the state road,” says Pologruto. “But the state highway will act like a water bed. The new overlay will be heavily distressed after eight or 10 years. So when we built our performance models in the pavement management system, assigning the structure type was one of the milestones in that development.”
Once a year, the agency directs the software to run through all the performance models to determine how best to invest the state's road improvement funds.
“You can't just design something this month and pave it next month,” Pologruto says. “That's why you need a pavement management system: to predict the condition so you can budget for the repairs.”