Maintenance is key element in transportation asset management plan
Iowa has more miles of public highways per capita than the majority of states in the nation, approximately 38 miles of road for every 1,000 people. The Iowa DOT is responsible for the state system, which includes roads designated as interstate, U.S., or state highways – including ramps, that’s about 9,400 miles of roads. Cities, counties, parks, or federal agencies are responsible for the remainder of the more than 114,400 miles of Iowa roads. The entire system has more than 24,000 bridges, with about 4,100 of those managed by the Iowa DOT.
Maintaining all those roads and bridges is a huge undertaking, especially since most of the system was originally built from 1940 to 1970. Much of the existing infrastructure was built with a design life of 40 to 60 years. Of course, that doesn’t mean we replace or rebuild a road or bridge once it reaches the end of its design life. Thoughtful stewardship, including careful maintenance, of our resources through the years can preserve these roads and bridges, our transportation assets, beyond their designed lifespan to get you there safely, efficiently and conveniently.
Maintaining pavements
In general, managing transportation assets such as roads and bridges is all about providing the right treatment to the right asset at the right time. Iowa’s sometimes harsh weather conditions and traffic load make preserving our transportation system especially challenging. Ken Morrow, of the Iowa DOT’s Office of Maintenance, said, “We do everything we can to extend the life of a pavement. Because of Iowa’s weather and our freeze-thaw cycle, preventing water from getting under the pavement through cracks in the road is one of the most effective things we can do to help a road last longer.”
You’ve probably noticed some black tar lines on older roads – those are sealed cracks. According to Larry Galehouse, the director of the National Center for Pavement Preservation, crack sealing is one of the most important treatments in an effective pavement preservation program. If the cracks are not sealed, water gets under the pavement and can cause potholes and other problems to develop when the weather changes from freezing to thawing. You can think about it like a house. If a roof leaks, eventually everything down to and including the foundation can be damaged. While a road may look like just a path of concrete or asphalt, there is a foundation underneath the pavement that can be damaged by moisture and the freeze-thaw cycle.
The Iowa DOT uses its own employees and contractors for projects that prolong the life of a pavement. Morrow said, “Over the years our workforce has gotten much smaller, but we still handle a fair amount of smaller crack filling and some patching projects. Larger maintenance projects are completed by contractors.”
Each of the Iowa DOT’s six districts has a set amount of money each year for smaller or emergency maintenance projects. The agency tracks detailed pavement management data on each road segment, including when it was built, what treatments it has received, and when those treatments were applied. “The managers in each district get together and go over the data and set priorities for the projects they want to accomplish that year,” said Morrow. “They are the ones who know their system best. Even though Iowa is a small state, the needs are much different in different parts of the state.”
The National Center for Pavement Preservation has concluded that treating a road at the first signs of deterioration is less expensive and can extend the life of the system. Think of it in terms of the exterior of a house. If you notice the paint is starting to crack, it is easier and less expensive to paint it sooner rather than wait until the paint is so damaged that the house must have all new siding. The same concept is true of pavements; we can pay a little now and prolong the pavement life or ignore the problem and pay a lot later to rehabilitate the road. While the life of the pavement can be extended somewhat by treating cracks, it can’t be extended indefinitely and eventually more extensive rehabilitation is needed.
Maintaining bridges
You may not think about it, but paint is an important component in prolonging the life of Iowa’s bridges. Paint preserves the steel that you’ll find holding up so many of the structures on our highways. Scott Neubauer, the Iowa DOT’s bridge maintenance engineer, said, “Cleaning and painting the steel on a bridge regularly helps prolong its life at a smaller cost. The paint we use now can sometimes last up to 30 years.”
For some bridges, paint isn’t the answer. Neubauer says weathering steel is a type of material that doesn’t need paint, but does need to be washed to remove corrosive materials. “This material is supposed to develop a thin protective layer called a patina that protects the steel. Salt and debris can prevent proper patina development, so we need to wash off the salt. For our border bridges, washing typically happens every year; other bridges are washed as necessary.”
Bridge maintenance projects, like larger construction projects as discussed in an earlier blog post, are scheduled, but on a short-time frame. While the larger projects are set in a five-year program, bridge maintenance projects are scheduled in a three-year time span. Neubauer said, “This allows us to plan, but have more flexibility to move a project around if conditions change.”
Getting the job done means maintaining our roads and bridges for the safety of travelers in Iowa. The Iowa DOT will continue to research the best methods for maintenance to assure our transportation assets remain some of the best in the country and that each dollar spent is spent wisely.
In our next transportation asset blog post, we’ll talk about how the bills get paid when it comes to our transportation assets.