A lack of funding will mean a decline in the safety and efficiency of Michigan's bridge network, the Michigan Department of Transportation warned this week.
Rebecca Curtis, MDOT's chief bridge engineer, presented the department's findings during a Wednesday meeting of the House Appropriations Subcommittee on State and Local Transportation. With less than $132 million allocated to bridge improvements, 2029 is slated to be the lowest bridge investment funding year, according to MDOT’s Five-Year Transportation Program.
Bridges are an expensive part of the highway network, and inflation costs have been very high, Curtis said. “Over the last 5 years, we’ve seen a 13% increase in the cost to replace a bridge each year.”
Inflation rates have outpaced any increase in funding, which has influenced how many bridges we are able to replace each year, Curtis added.
Past funding increases have never reached the amount needed to maintain a state of good repair over the long term, and in the past, preventive maintenance was not eligible for federal funding, so states had to use their own money to fix issues, Curtis said.
Many bridges were built when the interstate system was first implemented, so now about two-thirds of the structures in the state are over 50 years old.
Bridges must maintain a minimum condition to keep the transportation system open. MDOT said it has a robust inspection system where bridges are inspected every one to two years. As conditions deteriorate, these inspections can become more frequent.
The transportation department said record investments in bridges were being made in 2021, leading to improved bridge conditions along freeways, which it credited to Governor Gretchen Whitmer's Rebuilding Michigan bond program.
But the state now faces potential closures of around 100 bridges in 2035, impacting over a million drivers daily, Curtis said. According to MDOT, the current funding levels would allow the department to replace fewer than 10 bridges a year out of the 4,500 bridges in the state's network.
MDOT said it's begun identifying locations at high risk of closure over the next 10 and 20 years.
There are three components to consider when determining the condition of a bridge: the deck, which is the surface the vehicles drive on, the superstructure, which are the beams that support the deck, and the substructure. MDOT rates these components on a scale of 1 to 9, 9 being the best and 1 being worst.
Preventive maintenance is done on bridges in fairly good condition, where there are only minor defects like rusting on steel beams and cracks on concrete. According to Curtis, this typically costs around $200 per square foot.
More significant rusting, swelling, and potholes indicate that a bridge is in poor condition, which requires major rehabilitation. This usually costs more than three times as much — around $725 per square foot, Curtis said.
Closed bridges have defects so significant that public safety is at risk. These require emergency repairs.
The amount of bridges in good condition has decreased over time, according to data from MDOT. If a bridge gets bad enough, it will no longer be possible to do rehabilitation, and a replacement will be necessary, Curtis said.
“If we wait until 10 to 20 years later to address the problem, there will be too many bridges to replace at once, and we won’t be able to manage the inventory without closures,” she added.
According to Curtis, most local agencies do not receive enough funding to do a bridge project on their own. These agencies submit their cases on a competitive basis to MDOT’s Local Bridge Bundle program.
The program has around $50 million dollars of funding per year to support these local agencies. To date, all bridge bundles have been delivered on time and under budget, Curtis said.
As MDOT is considering next steps, the department said it's looking closely at the effects of potential closures. “We are looking to minimize impacts to communities and the economy, and best implement the limited funding that we have to minimize the negative outcomes,” Curtis said.
In general, around 60 to 70 bridges are closed at a time across the state, either temporarily for repair, or indefinitely.
“We are going to prioritize public safety and close bridges as they need to be closed,” Curtis said. “But even though we are doing all the right things, the funding is not there to help us move the needle enough.”
