Bridge Inspection Robot: From Snoopers to ABB

A bridge inspection robot is meant to take over some of the most awkward work in civil engineering: looking at every rivet, weld and bearing on a structure that hangs over water or traffic. For decades that has meant people in buckets on snooper trucks or on ropes under the deck. This post follows bridge inspection from the 1967 Silver Bridge collapse that created the US inspection program, through snooper trucks and rope access, to the drones and magnetic climbing robots now being tested. It also covers what ABB robots have to do with bridges today and where they could fit in inspection, which is still only a possibility.

A snooper truck lowers inspectors under the I-5 bridge over the Santiam River, Oregon, 2021. Photo: Oregon Department of Transportation / Wikimedia Commons (CC BY 2.0)

How inspectors reached bridges by bucket and rope

Before the late 1960s there was no national rule in the United States for checking highway bridges. That changed after 15 December 1967, when the Silver Bridge between Point Pleasant, West Virginia, and Kanauga, Ohio, fell into the Ohio River in rush-hour traffic and 46 people died. The 1928 eyebar suspension bridge failed because one eyebar cracked, from a flaw that the inspection methods of the time could not detect. The collapse led to the first national bridge inspection program, created in the Federal-Aid Highway Act of 1968, and inspectors have checked highway bridges on a regular schedule ever since.

The Silver Bridge between Point Pleasant, West Virginia, and Kanauga, Ohio, on a postcard from before its collapse in 1967. Photo: unknown photographer via Wikimedia Commons (no known restrictions)

The work itself stayed physical. Inspectors look for cracks, rust, loose bolts and damaged bearings, tap concrete with hammers to hear hollow spots and measure what they find, and most of that has to happen within arm's reach. To get under a deck they use a snooper truck, a vehicle parked in a closed lane with a folding boom that swings a bucket over the railing and under the bridge. Where no truck can reach, they climb. Oregon's transportation department, for example, trains its bridge inspectors for rope access certification on climbing walls before they join its rope team.

Oregon DOT bridge inspectors train on ropes for rope access certification, 2015. Photo: Oregon Department of Transportation / Wikimedia Commons (CC BY 2.0)

Automation arrived from the air first. Drones can photograph piers, cables and the undersides of decks without closing a lane, and in February 2021 the North Carolina Department of Transportation flew what it called its first drone bridge inspection beyond the pilot's line of sight, under an FAA waiver issued in 2020. Researchers also built robots that touch the steel. At the University of Nevada, Reno, Hung La's team designed a climbing robot with four magnetic wheels that holds onto steel members, carries sensors for navigation and mapping, moves at about 30 centimeters per second and was tested on a campus footbridge.

A drone view of a bridge during an inspection with GPS targets on the ground, 2022. Photo: FedericaGaspari / Wikimedia Commons (CC BY-SA 4.0)

Snooper trucks, drones and closed lanes in 2026

This autumn the routine looks much as it has for years. In Green Bay, Wisconsin, the Leo Frigo Memorial Bridge on I-43 was inspected from 14 to 17 September 2026, with one lane closed in each direction for two days at a time while inspectors, inspection vehicles and drones worked the span. WisDOT said the bridge was safe and no issues had been found. In Virginia, VDOT is inspecting the 1943 Falmouth Bridge on Route 1 from 5 to 9 October with alternating daytime lane closures. That bridge carries about 40,000 vehicles a day, and a major rehabilitation is being designed.

A snooper truck reaches under the deck during the August 2025 inspection of the Steel Bridge in Portland, Oregon. Photo: Oregon Department of Transportation / Wikimedia Commons (CC BY 4.0)

Drones are now part of these jobs, and on 1 October NBC Boston reported on how the MBTA uses them to assist with its inspections. A camera can spot rust streaks from a few meters away, but measuring how much steel is left under the paint or checking a crack needs contact, which is why snooper trucks and buckets are still out on bridges in Oregon, China and everywhere else. The climbing robots aim at that gap: the Reno group has published work on using a steel climbing robot to take ultrasonic thickness measurements on its own.

Bridge inspection trucks at work on national road G214 near Xiaozhongdian, Yunnan, China, 2024. Photo: Pieceofmetalwork / Wikimedia Commons (CC BY 4.0)

ABB does not make bridge inspection robots, and none of these inspections uses ABB machines. Its robots have built a bridge, though. MX3D printed its stainless steel footbridge with an ABB IRB 2600 and an IRB 6700, and the 12 meter span opened over a canal in Amsterdam on 15 July 2021. Partners including The Alan Turing Institute and Arup fitted it with sensors for strain, load, displacement and vibration that feed a digital twin. ABB arc welding robots also weld heavy steel parts in other industries, and our post on AI quality inspection shows how ABB arms already carry cameras to check parts.

MX3D's 3D-printed stainless steel bridge at Dutch Design Week. Photo: IIVQ / Tijmen Stam, Wikimedia Commons (CC BY-SA 4.0)

What climbing robots need before they replace the bucket

The likely future mixes several tools. Drones would survey the whole bridge, climbing robots would take contact readings on steel members, and sensors left on the structure, as on the MX3D bridge, would report strain and vibration between visits. Inspectors would spend more of their time reviewing the data and less of it hanging from ropes. In fabrication shops, where steel girders are made, robot arms could scan each part before it ships to give the bridge a starting record, a cell that would first be built and checked in RobotStudio.

An ABB arc welding robot with a positioner that turns heavy parts. Photo: Ana 2016 / Wikimedia Commons (CC BY-SA 4.0)

On the bridge itself, an industrial arm could one day ride on the boom of a snooper truck and hold an ultrasonic probe or a paint thickness gauge steady against the steel while the inspector watches from the deck. ABB arms such as the IRB 6700 are strong enough for that kind of tool, and SafeMove can limit where an arm moves and how fast near people. Nobody has published an ABB arm on an inspection truck, so treat it as a possibility. It would also need a sealed, weatherproof arm and a very stable boom.

An ABB IRB 6700 grinding a steel part in Teqram's EasyGrinder cell at Ancofer. Photo: ABB

Cost, safety and skills are the open problems. Magnetic wheels need clean steel, so concrete bridges, thick rust and flaking paint all cause trouble, and a robot that falls from a girder over traffic is a hazard. Drones need airspace permission and still need a pilot. Bridge owners will want to know that robot data is as reliable as an inspector's eye before they change their procedures, and inspectors will need training in reading scans and running the machines. For now the snooper truck and the rope team stay on the job, with drones and climbing robots working beside them.

Engineers with an ABB OmniCore controller and robot cell, the kind of training new robot crews would need. Photo: ABB

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