At least in Brazil, the speed limit is different for cars/motorbikes and for trucks/buses, often it’s a 3:2 ratio.
For example, a highway with a maximum speed of 130 km/h (very rare, max speed is often 120km/h) would have a maximum speed of 85 km/h for trucks and buses. This is often informed by the same vertical sign, e.g.:
“Veículos leves
120
Veículos pesados
80”
(translation: "lightweight vehicles: 120km/h / heavy vehicles: 80km/h)
If a truck is traveling at 100km/h in a highway whose speed limit (for cars and motorbikes) is 120km/h, the truck is committing a traffic violation.
Unfortunately, this happens a lot, with trucks often tail-following (is this the correct English terminology? I don’t remember) and threatening to run over a smaller vehicle which is trying to follow the laws and is traveling within the speed limits. People think “speed limit” means “required speed”.
Well, we do have countless accidents involving trucks on a daily basis, and those accidents often do cause the traffic to bunch up. One of the highways I’m somewhat used to drive through, “Rodovia Fernão Dias” (MG-460), is very famous for accidents in this regard. The accidents frequently involve retreaded tires (“pneu remolde”) popping off the truck’s wheels, and the truck is often traveling way beyond 80km/h (if they were traveling below 80km/h, maybe the truck would be slightly more controllable when such a thing happened I guess)…
In practice, the speed limit does nothing (except in cases they’re caught by a speed camera, but people deliberately de-accelerate when getting close to a speed camera before speeding up again). If people were to respect the speed limits all the times, especially the truckers, maybe, just maybe, accidents would be less frequent. The ones hindering safety are often the truckers, however, I don’t really blame them; the transportation companies they’re working to often push surreal demands unto them (e.g. “you must take this cargo from Santos to Belo Horizonte in 12 hours”, a 670km trip that’d take a car 10h non-stop, depending on the conditions of Rodoanel and Fernão Dias); they often use stimulant drugs (“rebite”) to keep awake during insane days-long trips, and sometimes you can spot a truck zig-zagging and veering off to the roadside because the trucker fell asleep.
!onehundredninetysix@lemmy.blahaj.zone