Ask a tank trailer operator why they don't run surge control, and cleaning comes up almost immediately. The trailer has to be washed out between loads. Adding anything to the inside of the tank means one more obstacle during that process, one more thing to work around, one more source of cost and downtime.

It's a real objection. It's also being applied to a category of hauler where it doesn't hold up the way people assume.

Two different problems wearing the same label

Compartmentalized haulers — fuel and gas delivery being the clearest example — are often cited as proof that surge isn't worth solving. When each compartment carries a full load to a single destination and is fully drained there, it stays completely full for the whole route until that one delivery. A full compartment has no headspace, so there's nothing for the liquid to move into and nothing to slosh. That's the condition where a compartmentalized hauler is right that surge isn't their problem.

But it's the full-load, single-drop pattern doing the work here — not the compartment itself. Any tank, compartmentalized or not, has the same "no surge" condition as long as it stays completely full until one full delivery. A compartment that makes multiple stops, dropping part of its load at each one, passes through a partial-fill state between stops and loses that protection — exactly the same as a single non-compartmentalized tank would.

Non-compartmentalized haulers typically don't have that guarantee at all. One tank, carrying a partial load — or loaded with something considerably heavier than what it usually carries. A chemical hauler switching products on the return trip. A fertilizer hauler running a heavier blend. An 8 lb/gal outbound load and a 12 lb/gal inbound load aren't just two different weights. They're two different volumes of liquid sitting in the same physical space, one of which now has far more mass and far more room to move than the tank was built around.

What the numbers say — and what they don't

FMCSA's Cargo Tank Roll Stability Study puts the national cargo tank truck rollover rate at approximately 0.13 rollovers per million miles driven, across all tank types and configurations. That's a low number. It's also the honest number.

But that figure is industry-wide. It isn't broken out for non-compartmentalized haulers carrying partial or mixed-density loads — the category carrying a standing surge condition rather than an occasional one. No dataset currently isolates that category's rollover rate. Until one does, nobody can say with precision whether this category's real risk is higher, lower, or the same as the industry average.

The real question isn't frequency

Low frequency doesn't mean low stakes. A rollover involving a hazardous product carries costs that don't show up in a per-mile average: a spill, a highway closure, a cleanup, potential injury or worse.

Comparing that outcome to routine cleaning cost on the basis of "how often does this happen" measures the wrong thing. The comparison that matters is what happens when it does.

That reframes the two questions worth asking across the industry:

Priority. Is cleaning cost being weighed against safety risk on the right terms — frequency versus a recurring expense, or severity versus a recurring expense? Those produce different answers.

Risk factor. What is the actual rollover and incident rate for non-compartmentalized haulers carrying partial or mixed-density loads specifically? Nobody currently has this number. It's worth finding out.

Where the fix might actually come from

The obstacle here isn't cleaning itself. Routine cleaning between loads of the same or compatible product isn't the disqualifier it's sometimes made out to be. The real obstacle is that many non-compartmentalized haulers — chemical and fertilizer operations among them — routinely rotate between products that are genuinely incompatible, requiring a full cleanout every time. And that rotation is currently driven by proximity: whichever backhaul is closest, not whichever backhaul is compatible.

A different question changes the routing logic entirely: not "what's the closest load back," but "what's the closest load back that doesn't require a full cleanout?"

That only works if compatibility data exists and gets used — matching which product pairs can sequence in the same tank with just a flush versus which genuinely require a full incompatible-commodity wash. If dispatch decisions started prioritizing compatibility over proximity, trucks might not return to their point of origin at all. They'd chain to whatever compatible pickup is next, even if that means a fundamentally different logistics pattern than the industry runs today.

That data, and that operational judgment, sits with the shippers and carriers who run these routes. What can be done now is name the problem precisely enough for the people who hold that data to see the opportunity in solving it.

An open question for the industry

Surge risk isn't something most non-compartmentalized haulers have ever been able to put a number on. They know surge exists. What they don't know is how large it actually gets — and the physics work against intuition here: surge force peaks at partial fill, not at full, which is probably not what most operators expect.

Surge risk is measurable. A solution is available. The number that makes the comparison meaningful is one calculation away.