Drone technology is being adopted by state departments of transportation at a rapid pace and being used in tasks ranging from predicting avalanches, mudslides and water runoff to pinpointing where to direct heavy machinery to clear roads after an event. Agencies are also performing routine inspections of vertical and linear infrastructure and highway crash reconstructions in a fraction of the time, compared to traditional methods, as well as identifying and avoiding endangered wildlife during road and bridge construction.

Ohio Department of Transportation is one of many DOTs across the country that is doing work faster, cheaper and better using drones. As a national leader in government drone use, ODOT dispatches pilots across the state from the Ohio UAS Center in Springfield. It also maintains pilots in three other high-demand DOT districts.

The state of Ohio is already seeing a good return on ODOT’s DriveOhio, Ohio UAS Center—a central hub for drone operations within ODOT. The Ohio UAS Center works with the U.S. Department of Transportation, Federal Aviation Administration and the Air Force Research Laboratory on multiple fronts and has been instrumental in evaluating and approving Ohio’s efforts for drone operations. With their support, under an FAA certificate of waiver or authorization, ODOT and the Air Force Research Laboratory are conducting beyond visual line of sight (BVLOS) flights up to 10,000 feet in a 200-square-mile operating area using a ground-based detect and avoid system at the Springfield Beckly Airport. The state of Ohio has invested more than $12 million in infrastructure and research to support drone operations and works closely with the FAA to further the development of the regulatory process.

One of the many ways ODOT is seeing strong returns on their investment in drones is using them for bridge inspections.

Ohio’s Drone Operations Model

ODOT’s pilots rely on a drone management platform to check airspace, plan flights and manage their drone program. Since adopting the tool in the fall of 2018, the agency has logged more than 1,360 hours with their pilots.

Most of ODOT’s budget for the UAS Center’s work is focused on transportation system preservation: maintenance, construction and snow and ice operations on roadways. But the department also shares its drone capabilities with other local and state agencies that are standing up drone programs or need flight operations support.

The Ohio UAS Center’s drone pilots help the Ohio Environmental Protection Agency with spills and debris piles. They also perform rollercoaster inspections at three theme parks for the Ohio Department of Agriculture, locate abandoned oil and gas wellheads for the Ohio Department of Natural Resources and provide disaster relief and searches for the Ohio National Guard. Additionally, the UAS Center has begun testing radiation detection using drones with the Ohio Department of Health.

Such capabilities are exciting, but state transportation agencies are finding the basic virtues of lower cost, efficiency and safety to be especially attractive.

The Bridge Inspection Backlog

Infrastructure inspections may not be as exciting as aerial avalanche monitoring, but they do allow for some of the most exciting returns on investment from drones. Plus, there’s still a lot of work to be done.

Safety inspections must be done at least once every two years for highway bridges that are over 20 feet long and located on public roads. This federal rule was put in place following the rush hour collapse of the Silver Bridge over the Ohio River in 1967, the deadliest bridge failure in the U.S. on record.

But transportation agencies are having a hard time keeping up. Collectively, the nation’s bridges are way past their prime. Nearly 235,000 bridges, about 38%, need repair, replacement or major rehab, with roughly 46,000 bridges rated structurally deficient.

Ohio is home to nearly 26,000 bridges that meet the federal definition and 45,000 that meet the state’s definition, representing the second largest inventory in the U.S. Ohio planners calculate there are about 650 self-identified candidate bridges for drone usage.

To figure out if drones could be used to speed up bridge inspections and yield cost savings, ODOT compared the cost of traditional inspections to the expected ROI for drone bridge inspections.

Costs of Traditional Bridge Inspections

Using the standard snooper truck method, a field crew of six to eight is involved. This includes highway technicians for safety and two or three inspectors positioned in the lift. If the work involves a railroad bridge, a flagger is also employed to monitor for coming trains. Rental fees on some equipment, traffic signs and cones can introduce additional costs.

A typical inspection takes a full day, roughly 48 labor hours, and in the case of on high-traffic bridges, work is often completed at night or on the weekend, incurring overtime. Working on roadways introduces safety risks for anyone in the area—crews and motorists alike.

“When you’re using a snooper truck, you’re closing down lanes,” says Dave Gallagher, ODOT drone flight operations manager. “It’s a risk for those working the lane closure and also a risk for motorists driving around.”

Costs of Drone Bridge Inspections

When using drone technology, just two field workers are needed for bridge inspections. This has been a key advantage during the COVID-19 pandemic, when the snooper truck could not always be used due to any one entity, weather delay, mechanical breakdown or COVID-19 case.

Inspections are done live, with the technician looking at video streamed from a drone-mounted camera.

“Our bridge inspector pilots know what to look for, and know when something needs closer inspection,” says Helen McCreary, ODOT UAS program analyst. Photos are also collected in a precise order so they can be organized according to location on a bridge. “The photo quality is better, we get closer and see a lot more,” she adds.

Return on Investment for Drone Bridge Inspections

“You can’t quantify the safety comparison,” McCreary says. “On the one hand, you have two guys under the bridge flying a drone versus eight guys on top of the bridge working alongside high-speed traffic. It’s potentially saving lives.” Additionally, the tradeoff is the four to six people who would not be performing traffic control for an inspection requiring mechanical access would instead perform other beneficial duties in the county to preserve the highway system.

For comparison purposes, to figure ROI for bridge inspections, ODOT estimated the number of bridges that could be inspected over the lifetime of a drone at 100. Calculated this way, the cost of the drones came to $45 per bridge inspection. As for labor, drone bridge inspection takes about eight labor hours, with ODOT crews often completing two or three per day.

Because drones can’t replace every type of bridge inspection, McCreary expects that half of the work will still be conducted using the mechanical access approach. The savings on equipment and labor by using drones for the other half are compelling. McCreary estimates that ODOT realizes annual savings in excess of $400,000.

Drones are making transportation projects smarter, speeding up road maintenance and making public money go farther. As a national leader in government drone use, Ohio is laying a foundation for other agencies to follow and with so much infrastructure at stake, state DOTs are certain to continue to be among the top beneficiaries of drone technology. What new and innovative drone use cases are on the horizon for state DOTs? There’s no time like the present for companies to explore how to continue pushing the envelope on performing safer and more efficient bridge inspections with drones.