16 hours is generally not allowed unless there are severe adverse conditions, but it's only recently with ELD (Electronic Logging Device) mandates that these rules are being forced to a degree. Before that, many drivers would simply go as many hours as they humanly could to keep moving.
It's mostly around engineering whether you have enough downtime to "move" your "driven" hours into.
For long-haul it's probably a bit different, but other routes have a lot of annoying delays.
E.g. waiting at a port, waiting for a trailer replacement, waiting for receiving, etc.
Afaik, these are all classified as driving hours for logbook purposes.
It creates a situation where you legally have to park a truck on the side of the road when you hit your cap, even though 1/2 of your day might have been waiting around for something.
Imho, that's a bit ridiculous, and I'm sympathetic to shadow logbooks there.
For the 16 hours straight cross-country pounders, less-so. But long-haul is what autonomous trucking will likely eat first.
The toll it takes on your sleep schedule is also brutal, because the rule is 10hr on / 8hr off. If those 8 "off" hours happen to coincide with sleeping hours you might get some rest but that won't be frequent, or enough. It would be better, smarter, and safer to just drive 16hr and then sleep for 8hr. But the rules are the rules, they don't have to make sense.
much of my extended family was in teh trucking industry one way or the other. Before the electronic books you had manual log books. Lying in your log book was a very big deal, i want to say you could get in trouble with the law in addition to getting fired. Before that though it was even more the wild west than it is now. My step-father knew my grandfather's "outfit" and he would joke that if they had a chain long enough to go around it they would haul it no questions asked.
See: https://www.fmcsa.dot.gov/regulations/hours-service/summary-...