As infrastructure spread across America in the 20th century, we learned that bridges periodically need to be inspected. Having a look at the road surface was easy; just shut down traffic and let the inspector walk it. But inspecting the underside is more challenging, particularly if the bridge is tall and/or over water.

Ideally all bridges would be built with inspection catwalks beneath them, but that requires far-sightedness and adds cost. Absent catwalks, you've got a problem. Your most experienced inspector is likely to be older, while climbing underneath a bridge is more easily accomplished by a younger person. And no matter who it is, that person needs to have additional training in climbing and rigging.

This problem was solved in 1964 by the startup Paxton-Mitchell Co., which invented this Snooper truck:

This became the go-to solution for many municipalities across America, and Nebraska-based Paxton-Mitchell continues making them today. (The company claims that they're "the world's most widely used Underbridge Inspection and Maintenance Truck.")

Today's versions can reach depths and horizontal spans unimaginable in 1964:

The 2024 versions can be outfitted with a variety of boom and platform types, with or without outriggers, depending on the site's needs:

I imagine underbridge inspections will be all drone-based in the near future, beaming footage back to an inspector on the ground. But as long as human workers are needed to perform the actual repairs, demand for Paxton-Mitchell's vehicles will continue. However, if the company wants to be proactive about obsolescence, they should gradually pivot towards developing crawling spider-bots that can weld.