Federal highway engineers are designing America’s roads for a climate that no longer exists.
The county blacktop a mile down the road went soft at the edges by Tuesday afternoon. The notebook has the heat index for the day at one-oh-four. Not buckled, not yet. But the road felt different from the road the design manuals were written for. The same heat that did the work on a Maryland interstate on July 3 was doing the preliminary work on Highway 13 in Adams County the same week, and the country is going to have to decide what to do about both.
A southbound lane of Interstate 97 near Annapolis buckled the afternoon of July 3, snarling holiday traffic into Maryland. A city street in Chicago buckled the same day. State departments of transportation from the Plains to the Atlantic warned drivers to watch for additional heat damage through the holiday weekend. The pattern was not a fluke. Civil engineers who spoke to NPR about the failures said the same thing in three different ways: the country’s roads were designed for temperatures that the climate is now exceeding, and the design standards have not caught up.
Charles Marohn, the Minnesota engineer who founded Strong Towns, told NPR what happens when a road is built for one climate and asked to perform in another. When water gets under the pavement, the base gets soft. Add prolonged heat, add heavy traffic on top, and the pavement expands and breaks. Marohn said concrete — the rigid pavement that carries most of the interstate system — fails “really bad, really quick” when it does fail. Asphalt deforms more slowly but in different ways, forming ruts where trucks sit in the sun at intersections. Either way, the road was built for a temperature range the climate has moved past.
Amit Bhasin, who runs the Center for Transportation Research at the University of Texas at Austin, said anyone can design super-robust roads. The country could choose to design for extreme events. The cost would be higher. The choice the country has made is to accept occasional disruptions in exchange for affordability. That is the choice I want to name.
It is the same choice the country made when it built the electric grid for a load profile that did not include air conditioning as the default. The engineers who set the design standard in 1972 were not being cheap. They were being honest about what the data they had supported. The engineers who set the design standard now have the data and are not updating it. That is where the wrong is.
Mikhail Chester, the Arizona State engineering professor, put the same point a different way. “We’ve designed our infrastructures over decades, if not centuries, for temperatures that have been relatively milder.” Chester said the past approach “doesn’t seem to be sufficient” for the future. The interstate was a deliberate act of national will, built to a deliberate set of design standards, paid for out of a deliberate federal funding mechanism. The design standards are the policy. The funding mechanism is the policy. The failure to update both, as the climate moves past the standards, is the policy. It is not a meteorological event. It is a decision the country has not made, and the cost of not making it shows up as a buckled lane on I-97 and a closed street in Chicago and a county road in Wisconsin whose edges go soft in the heat.
Wendell Berry, in The Unsettling of America, named the analytical pattern that fits the road version of the problem. Berry’s argument is that the rules a rural economy runs by get written by and for the consolidated operator, and the small operator does not lose because the small operator is less wanted by the people who depend on it. The small operator loses because the rules of the game are written to make the small operator unable to clear the bar the rules set. The road version of the pattern runs as follows. The interstate gets the engineering attention, the federal funding, the design standard. The county road gets whatever the county can afford on top of what the state sends down. The county road’s design temperature was set to the same range as the interstate’s. The climate the county road now sits on is the same climate the interstate is buckling on. The county road does not get the upgrade the interstate is contemplating. The county road does not get the engineering study. The county road, when it fails, gets the sign that says ROAD CLOSED and the four-mile detour.
Aldo Leopold, in “January Thaw” from A Sand County Almanac, wrote about the year the ice on the farm pond went out early and the year it went out late and what the difference meant to the wildlife that depended on the calendar of freeze and thaw. Leopold was not writing about highways. He was writing about what happens to a system when the calendar the system is built around stops matching the weather. The roads of the country were built to a calendar of heat extremes. The heat extremes have moved. The ice found new patterns. The roads, so far, are finding buckled lanes.
The notebook has a different entry. The pavement thermometer at the shop lot read one-thirty-six at two in the afternoon one day in late June, with the air at ninety-one. The road surface was running forty-five degrees above the air. The design temperature the road was built to handle does not exist in the climate the road now sits in. The notebook does not record the name of the engineer who set the design standard. The notebook records what the road does at the temperature the climate is now producing.
The choice Bhasin named is the choice the country is not making. The country is choosing to keep designing roads for the climate it had, knowing the climate it has is different. The country is choosing to call the difference an “affordability tradeoff” rather than a deferred maintenance bill. The bill is coming due. It came due on I-97 on July 3. It will come due on Highway 13 south of Adams County one summer soon, on a stretch of blacktop that has carried three generations of Wisconsin traffic. When it does, the engineers will say the failure was a one-in-fifty-year heat event. The notebook will record that the one-in-fifty-year event has now happened three times in the notebook’s twelve years. The cost of the deferred choice is what the road does in the heat the design manual did not plan for. The country can keep calling that an act of nature, or it can call it what it is: a policy decision, made by not making it, that lands on whoever is on the road when the lane gives.