That's not hazardous at all. Two vehicles and a line of cars behind them all going the same speed sounds quite safe to me. That's zero speed differential.
It is hazardous. You're forcing vehicles to slow down from the speed limit (70 - 75 mph) down to 65 mph sitting behind this truck having no way around. In theory, it's all safe, until you have impatient drivers tailgating and performing unsafe maneuvers, etc. Yes, those unsafe maneuvers may be illegal, but people will still do it (that's just a fact) and the likelihood of a wreck is a lot higher.
I've always been again speed differentials and I will continue to be. Many would agree. It's dangerous. That's just the fact of the matter.
By promoting a single speed limit, you are ostensibly supporting all trucks going 70 or 75. But many states have governors for fuel or other reasons, so you'll still have a bunch of variation, which according to you:
is hazardous, and quite frankly should never happen.
Yes, I understand governs exist on some trucks nowadays, and states have slower speed limits (infamously California still having 55 mph for trucks, which is almost never obeyed). I don't agree with those either, but the trucks that aren't governed, the majority of states that don't have truck speed limits, and the independent truckers who aren't governed - they should be able to keep that and not be forced onto some universal truck speed limit system. That's my issue.
In Germany, trucks are simply not allowed on Autobahnen except at night. That simply won't fly in the US where we insist on same-day or next-day delivery from Amazon. Whenever possible, it would be ideal for trucks to have a separate roadway from other vehicles. The cost of that (except to avoid a lot of "trucks in the wrong lane" bypasses) is prohibitive. So, what can we do? Well, California gives trucks a lower maximum speed. I am not sure that it is necessary, but, it also restricts them to the right lane. That's the next best thing to giving them their own roadway. Cars mostly say out of the left lane when trucks are around. Trucks mostly stay out of the farther left lanes when cars are around. I'd like to see more tickets for trucks not in the right lane and I'd like to see more tickets for cars cutting off trucks and using the right lane to cut in.
But, as I have said before, we need to keep trucks moving and trucks need not to hold up the show for other vehicles. Trucks that can't go 70 MPH don't belong in a lane where cars can legally go that speed (and flow of traffic is often a good bit faster).
What I see on I-5 is that there are a large number of trucks in the right lane going 65-70MPH (in a 55 MPH max zone), just humming along trying to get their loads to the place where their loads belong and they become hindered by a truck (often fully loaded and possibly with some mildly hazardous materials) that barely is able to go 55MPH. So, the trucker gets annoyed as many of us would about Overloaded Overstock holding up the show. If I have to go 54 all of the way to Sacramento, it will take me more than an hour longer than I have allowed. The loaders will have gone home. I won't get a good seat in the poker game. My wife will have gone to work. I will miss Oprah. Whatever. So, trucker finds what looks to be a hole in the left lane stream and starts to move into it. Of course, within seconds, Fast Eddie (in his Viper) has closed the imaginary gap. Monster Mich and Joe Cool are right behind him and start to get annoyed even more so at Eddie for letting the trucker in and even before the trucker has moved all of the way into the left lane. Now, because Over has slowed the trucker down to 54 MPH, it takes a little while for trucker to get up to his normal 65-70 and he may even go just a bit faster to get the pass over with before Eddie, Joe, and Mich open fire on the trucker with automatic weapons, but the guy in front of Overstock hasn't yet seen the clear space, so trucker either has to pass him as well or has to wait while he creates the gap. In the two or three minutes that this takes, the left lane gets backed up in ripples all of the way back to the I-5/CASR-99 split.
