33-foot doubles? Not here. Not now.

FedEx, UPS, Amazon, and some LTL carriers want the feds to allow the 33-foot doubles legal in some states to be used nationwide. That would mean 5 more feet of capacity over the current 28. More freight and more revenue at little extra expense for carriers.

Trouble is you can’t add capacity inside without adding length outside. Since doubles necessarily travel in twos, adding 5 feet to each means an overall length increase of 10 feet. Imagine asking Congress to increase the 53-foot semitrailer limit to 63 feet. Think you would get anywhere? Neither do I.

Yet some lawmakers are listening. After all, 33-foot proponents have arguments from experts, including experienced truck safety consultants. To be sure, they do know what they’re talking about, but knowing the subject and being right about policy are not the same thing.

In a 2017 transportation journal essay, one expert calculated 33s would provide 18.6 percent more capacity, which translates into 3.1 billion fewer truck miles, 255 million fewer gallons of fuel and 2.9 million fewer tons of carbon dioxide emissions. That would be like taking more than half a million cars off of the road. Overall, he noted, consumers would save $2.6 billion in delivery costs.

One consulting firm claimed 33s could reduce greenhouse gas emissions by 10 percent and highway congestion by 14 percent.

Wow.

Extravagant extrapolations are often used to woo lawmakers but they rarely work out in reality, which introduces variables not even experts can anticipate. Anyone who has been in trucking for a while knows about variables at a near-instinctive level. Trucking is a perpetual battle against fate itself. Even the variables have variables.

It’s important to understand that adding 5 feet doesn’t mean that 5 feet will always be used. Loading trucks high and tight depends on lots of, well, variables. What kind of freight are we talking about? Is it heavy stuff? If so, you might not fill all 33 feet in any case. Are we talking about pallets or floor loads? Is it the kind of freight LTLers call “misc” for miscellaneous? How does the freight have to be loaded – in any order or in a routed sequence? Who is loading the trailer? Efficiently loading mixed freight is an art that comes only with experience. Finally, does that trailer have to leave at a specific time? If so, will it always be loaded out before that time arrives?

Calculating that extra 5 feet per trailer into 14 percent less highway congestion is absolutely giddy. Of course there would be savings. But if they were as great as claimed, why stop at 33 feet? Why not 40 feet? Why not 53?

Because they would be ridiculous, that’s why. Long combination vehicles (LCV) may work on a Wyoming interstate, though I’m sure they can be a pain in the ass even there when you’re trying to pass them. Longer LCVs are already legal in many sparsely populated states. The idea here is to make them legal everywhere, even in the most populous states. But conditions on, say, I-80 in Wyoming are not the same as I-80 in New Jersey. If you’ve driven I-80 in Jersey, you know what I mean.

That’s why New Jersey and other crowded states didn’t allow 28-foot doubles until the feds forced them to in the 1980s. They’re still a bad idea. Now big trucking – though not necessarily the truckload sector – wants to force 33s on them.

But the costs would clearly outweigh the benefits, even though those costs might not be calculated in truck miles or fuel savings. Double 33s would impose costs on the public, especially at highway entrances, exits, and wherever lanes merge. Those costs will be measured in inconvenience, fear and genuine peril. In some urban circumstances, they’re already caused by single 53s and even more so for double 28s. It can only get worse with double 33s.

When I was a young driver, the standard trailer length was 40 feet. A handful of the old 35s were still around. The new 45s were starting to show up; the 48s were just around the corner. Those increases came as American roadways were improving, the interstates made long-haul trucking viable, as cities and states – often with federal money – eased local bottlenecks. Longer trailers were justified by infrastructure improvements.

Today, with few exceptions, the opposite is true. Road quality is deteriorating even as it carries more traffic – sometimes more than it was designed for. Truck traffic is so dense on some East Coast interstates it’s like driving in one, dreary, never-ending convoy.

More trucking efficiency pays, of course. That may justify the massive investment in new power, digital routing and freight handling technology we see today. That’s how UPS, FedEx, and the others should reach their efficiency goals – not by inflating their already fat footprints on our roads.

And if there ever will be a time to do that, which I doubt, it sure as hell isn’t now.