Was talking to my buddy, who's an iron worker, about how much safer his and other construction industries have gotten in the last 100 years, and the national highway system came up. Neither of us could think of ever hearing a number, and both Google and searching Reddit comes up empty. Any one of you have any sources on this or anything?
There's no way to come up with a firm number, as the network of highways in the US was built over a period spanning centuries, by many different companies and agencies. Even if you're talking only about the Interstate System, those were built by hundreds of firms under the direction of 50 different state highway agencies plus assorted tollway authorities, and in many cases were merely upgrades of roads that already existed.
In the first half of the 20th century, bridgebuilders had a very rough (and somewhat morbid) prediction that a large project would cost a construction worker's life for every million dollars—but few roadbuilding projects involve underwater digging (for support piers) or steel work high in the air.