Texas recently finished getting rid of the "Trucks must go slower than other traffic" crap.
Letting Wikipedia cover the history:
https://en.wikipedia.org/wiki/Speed_limits_in_the_United_States_by_jurisdiction#Truck_speed_limits
Texas once had separate, systemwide truck speed limits, but they were repealed in 1999 and 2011.
The truck speed limit used to be 60 mph (97 km/h) day/55 mph (89 km/h) night when the regular limit was higher. This speed limit did not apply to buses or to trucks transporting United States Postal Service mail.
Truck speed limits disappeared when all speed limits were capped at 55 mph (89 km/h) in 1974. They reappeared with the introduction of 65 mph (105 km/h) limits in 1987.
Effective September 1, 1999, Texas repealed truck speed limits on all roads except farm to market and ranch to market roads.[168][169]
In 2001, a bill allowing 75 mph speed limit on roads in certain counties excluded trucks, introducing a 70 mph truck speed limit on roads with a higher limit.[170] A bill in 2005 allowing 80 mph speed limits still excluded trucks.[171] However, truck speed limits were fully repealed in 2011.[172]
Night speed limits
Before September 1, 2011, Texas had a statutory 65 mph (105 km/h) night speed limit on all roads with a higher daytime limit. In 2011, the Texas Legislature banned night speed limits effective September 1, 2011.[172] However as of June 2013, night speed limits (55) were retained on some county roads where the speed limit is 60 mph in Scurry County, just outside of Snyder, Texas.
When we had the separate speed limit for trucks, we didn't see
any statistically significant safety benefits and in fact had more than a few problems. The Texas truck speed limit being slower than the car limits led to a rise in rear end accidents where the car would attempt to go under the back of the trailer or truck despite the ICC/Mansfield bar (which was actually set up for the larger cars of the 1960s and smaller modern cars actually can go under it - and decapitate the occupants). We've actually had a small general
reduction in rear end hits on trucks with the removal of the truck speed limits.
On a more mundane basis, the speed differential was absolute garbage in practice. Texas has a lot of two lane roads - so you'd end up getting stuck behind a slow ass tractor trailer and praying for a passing zone to come up. Texas had a lot of left exits - though they're being removed as interchanges and roads get rebuilt - so you'd get a 65mph truck merging into a 75-80mph (or faster, despite the posted limits) traffic stream to get to the left exits and traffic would back up for literal miles behind the damn thing in no time. A heavily laden 65mph-limited truck also can't get a run up on the flat leading to a hill so it could try to maintain speed better - nope, it's going to start crawling as soon as it hits the hill, causing a massive tailback yet again.
Let me remind you that this is still what typical Texas highway traffic in this area looks like. I'm doing 80, about the prevailing flow of traffic in the middle lane, in a posted 70 zone, and I'm
still getting passed.
Throw in every semi now being stuck with a damn near 20mph speed delta becoming unwanted rolling roadblocks and that's going to be very bad for traffic and crashes.
As far as I can recall, there has been no statistically significant increase in road fatalities involving tractor-trailers that can be linked to the removal of the truck-specific speed limits in Texas. Our major life safety issue with semis in Texas at current, as best I can recall, is not speed but Mexican trucks - between
human smuggling cargoes dying in the heat, drug smuggling, questionable documentation (forged documentation presented by unqualified drivers) and the occasional completely unsafe brake repair, speed (especially in the era of legally mandated GPS monitoring and automatic logbooks!) is way down on the list of truck problems needing to be solved.