The Choreography Of Pavement Maintenance

By Brent Whitwell, Midwest Testing | September 28, 2010

The merging of technology with the trained eye of an engineer is a beautiful thing, although it can make for an odd sight. Earlier this year on parking lots across St. Louis, it gave the appearance of aimless wandering. Yet, there was high purpose in every step, every glance and every input made to a GPS palm pilot: to save money on pavement maintenance.

Now being introduced to the St. Louis business community is Cartegraph — a program Midwest Testing is deploying as part of its Pavement Management Program. Cities and county governments have used the cost-saving technology developed by the Dubuque, Iowa-based company since its founding in 1994. Now, it is finding a place in private industry where firms like St. Louis-based retail development giant THF Realty are looking for smarter ways to maintain thousands of acres of parking lots and access roads.

The needs of THF are not unlike those of a city. The firm manages more than 24 million square feet of commercial space — the vast majority of it retail — in 20 states. The access roads, parking lots and sidewalks leading to each function as their welcome mat. Yet, given relentless 24/7 exposure to the elements, these welcome mats can be uninvitingly expensive to maintain.

Take a typical asphalt parking lot, for example. Depending on how it is constructed, a parking lot can go through 75 percent of its lifespan and see a decrease of around 60 percent of its initial condition. The last 25 percent of its lifespan, though, can see degradation accelerate rapidly and the remaining 40 percent of the pavement's condition is lost over a much shorter time span.

Waiting to maintain a parking lot until its condition has dropped below a critical level can mean huge differences in costs, differences on the order of five to six times just to make it look respectable again. But what if you could invest those maintenance dollars effectively and greatly increase the life of the pavement, making it useful for years to come? That's where the engineer, GPS, Cartegraph, and the meandering walk on the parking lot come in.

Armed with the GPS palm pilot, the engineer walks and photographs every square foot of the parking lot, inputting signs of deterioration. The trained eye of the engineer is needed to identify alligator cracking, snake-like transverse cracking, block cracking and areas of standing water, and other signs that can accelerate degradation. The engineer also notes traffic patterns, since usage has a dramatic impact on pavement life.

For example, just one 80,000-pound truck per day causes as much wear and tear as 5,800 cars per day over the span of a year. Repeated stress at that level greatly reduces the lifespan of pavement.

Once the parking lot is mapped, complete with specific areas of significant deterioration, the information and images are entered into the Cartegraph program on an office computer. Cartegraph then applies the standard created by the U.S. Army Corps of Engineers for measuring pavement conditions — the Pavement Condition Index (PCI). Each segment of the pavement is given a PCI.

Other inputted information includes the date the pavement was installed and its history of maintenance, along with other useful information such as pavement width, segment length and pavement classification. Cartegraph then creates a maintenance schedule to optimize the life of the pavement based on its PCI.

Images of each segment are included in the program so the engineer and the owner can visualize the section for each maintenance program.

Cartegraph also creates multiple budget scenarios and outcomes — for the current year or for the next three, five or any number of years — to help owners allocate maintenance funds. It also has the capability to create "what if" scenarios to develop a multiple-year work plan that optimizes each maintenance dollar. In sum, the ability of Cartegraph to quantify the economic benefits of preventative maintenance makes its money-saving "stitch in time saves nine" approach to pavement maintenance a viable reality.

What starts as aimless wandering is really a precision choreography between the trained eye of the engineer and Cartegraph. The engineer's observations are invaluable in identifying prolonged, temporary changes in traffic patterns; areas subjected to concentrated heavy truck traffic; drainage issues; and inferior construction materials and practices. It becomes a dance of detail to produce Cartegraph's "best practices" output and optimize the benefits of an extremely useful and powerful program.