Can you imagine a truck struggling uphill having to pull over and *stop*? I mean more than likely he is in his best gear at his best torque and best RPM doing his best speed. If he pulls over to let traffic pass he will *never* get back up to the speed he had before. Remember, a big rig almost always has some forward momentum when they *start* uphill. If they started from a dead stop at the base of a hill they would probably never get close to the speed they had before getting off the road.
I forgive big rigs that don't use pullouts going up hill and a law against that is just narrow thinking in my opinion.
Keep in mind that if the truck can't get started from a dead stop on the hill then he is exceeding his capabilities and shouldn't be on that road to begin with -- What if a road incident forces the truck to stop and it can't get going again? -- Bet he/she gets an impeding traffic citation -- I find it hard to imagine that a professional truck driver would deliberately put him/her self in that position -- That's why they have trucker's atlases with the grades in them. That forward momentum is not likely to last long, esp on grades that are miles long -- We amateurs can do that sort of thing, riding the wrong edge of the margin, but professionals won't stay in the job long if they don't do it right .
Not all vehicles and loads are suitable for all roads and this kind of law is making the driver responsible for knowing what he is doing.
This is real trip planning, planning to cross the high passes at night when the air is cold and dense giving more power and less overheating potential, plus not having as much traffic around to impede. I know I had to take those factors into account with my rig in Colorado when I was having some power problems.
I know one of the tests Chrysler has for its tow ratings is to do just that -- Bring truck to dead stop on very steep test hill towing full rated load and get it going again.
LEOs I personally know are big on keeping traffic flowing and a long snake behind a vehicle that isn't hacking it is clear evidence of impeding the flow. The same LEOs exercise judgment when writing citations.
Of course, some of the snake heads may be folks who are towing over their limits (adjusted for altitudes) and reporting no problems, perhaps because it's not a problem for them, just the others on the road behind them.
I believe Alaska has the same sort of "five behind is too many" laws and reportedly the highway patrol is quick to write tickets.
How many states and provinces have a "five is too many use pullouts" law? So far we have Washington, Alaska and now Colorado and I believe there are others.