Drone technology is being adopted by state departments of transportation (DOTs) at a rapid pace. In 2016, not a single state DOT had incorporated drones into daily operations. Just three years later, nearly three-quarters of these agencies had in-house drone programs.
DOTs are using drone technology in diverse and fascinating ways:
- Predicting avalanches, mudslides, and water runoff — and pinpointing where to direct heavy machinery to clear roads after an event.
- Performing highway crash reconstructions in a fraction of the time of traditional methods.
- Wildlife inventories: finding and avoiding nests of endangered birds before road construction, or checking for protected bats under bridges.
- Routine inspections of vertical and linear infrastructure — salt barns, signage, light poles, pavement, and bridges.
The state of Ohio is already seeing a good return on its Ohio UAS Center — a central hub for drone operations within the Ohio Department of Transportation (ODOT). ODOT is one of many DOTs across the country that is doing work faster, cheaper, and better using drones.
Here’s one of the many ways ODOT is seeing strong returns on their investment in drones: using them for bridge inspections.
Ohio’s drone operational model
ODOT is considered 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.
ODOT’s pilots use Skyward’s drone management software to check airspace, plan flights, and manage the drone program.
“We’re using the Skyward platform to do our risk assessments, our flight scheduling, our flight planning,” said Rich Fox, Airspace Manager at ODOT. “In total, since we have started using Skyward, we have logged 990.3 hours with our pilots” as of November 2020.
Most of ODOT’s budget and the UAS Center’s work are directed to 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 Center’s drone pilots help the Ohio EPA with spills and debris piles. They perform rollercoaster inspections at three theme parks for the Ohio Department of Agriculture. They locate abandoned oil and gas wellheads for the Ohio Department of Natural Resources and provide disaster relief and searches for the Ohio National Guard.
No doubt, there’s a cool factor that comes with such capabilities. But it’s the basic virtues of lower cost, efficiency and safety that have made drone technology so attractive to state transportation agencies.
The bridge inspection backlog
Infrastructure inspections aren’t exciting like aerial avalanche monitoring. But they are where some of the most exciting returns on investment (ROI) from drones are coming. And there’s a lot of work to be done.
Safety inspections must be done at least once every two years for highway bridges over 20 feet long 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. The nation’s bridges as a whole are way past their prime. Nearly 235,000 bridges, about 38 percent, need repair, replacement or major rehab, with roughly 46,000 bridges rated structurally deficient.
Ohio is home to nearly 45,000 bridges, the second largest inventory in the US. Ohio planners calculate there are about 1,600 in the state with significant deterioration of the bridge deck, supports or other major components.
To figure out if drones could speed up bridge inspections and be cost effective, 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, including highway technicians for safety and two or three inspectors to go up 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 are also cost items.
An inspection takes a full day, roughly 48 labor hours. On high-traffic bridges, the work is typically done at night or on the weekend, incurring overtime. And working on roadways can be dangerous.
“When you’re using a snooper truck you’re closing down lanes,” explains 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 the number of people required to operate it safely.
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
To figure out drone 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 classic 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.
“And you can’t quantify the safety comparison,” McCreary adds. “On the one hand, you have two guys under the bridge flying a drone versus eight guys on top of the bridge with angry traffic going by with everybody mad about having a lane closed. It’s potentially saving lives.”
For a deep dive into how ODOT calculated this ROI, and to hear about more of ODOT’s use cases, watch ODOT’s on-demand webinar with Skyward.
Drones are making transportation projects smarter, speeding up road maintenance and making public money go farther. With so much infrastructure at stake, state DOTs are certain to continue to be among the top beneficiaries of drone technology.