Snooper Trucks: Specialty Vehicles for Underbridge Inspections

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...