Oversize & Overweight Freight, Explained

"Oversize/overweight" (OSOW), "oversize dimensional" (OD), and "heavy haul" all describe the same thing: a load too big or too heavy to move under a state's standard legal limits. Once a load crosses any of those limits, it needs a state permit — and often escorts, route surveys, and travel restrictions on top. Here's how the whole thing works.

1What makes a load oversize or overweight

Every state sets legal limits for how big and heavy a truck can be without a permit. The federal baseline on the Interstate system is a common starting point, but each state sets its own numbers for non-Interstate roads:

The catch: these limits vary by state, and the numbers that matter are the overall dimensions of the whole rig — tractor, trailer, and the freight, including any front or rear overhang. A load that's legal on the trailer can still be oversize once you add the deck height or the overhang.

2When you need a permit

If a load exceeds any legal limit in any state on its route, it needs an oversize/overweight permit from that state before it moves. Permits are issued per state, so a Houston-to-Denver move touches several permitting agencies, each with its own limits, fees, and rules. Standard single-trip permits are usually issued quickly; the bigger the load, the more review it needs (see superloads below).

3Escort vehicles & pilot cars

As a load gets bigger, states require more help moving it safely. The escalation generally looks like this — though exact thresholds vary by state:

• Flags & signage — required on almost any oversize load (banners, flags on overhang, sometimes amber lights).
• One pilot car (escort) — typically once a load reaches roughly 12–14 ft wide, or a certain length.
• Two escorts — front and rear, usually around 16 ft wide or on longer loads.
• Height pole — a lead escort running a pole set to the load height, to catch low wires and bridges on tall loads.
• Police escort — for extreme widths or loads moving through dense urban corridors.

Each state publishes its own width, height, and length triggers for these — part of why a multi-state OD move takes real planning.

4Route surveys

For tall, wide, or very heavy loads, states may require a route survey before issuing a permit — a physical or engineered check of the route for low bridges, tight turns, weight-restricted structures, and utility lines. It confirms the load can physically make the trip, and it's a standard step once you get into superload territory.

5When you can (and can't) move

Permits come with travel restrictions:

• Daylight only is the norm for oversize loads — usually 30 minutes before sunrise to 30 minutes after sunset.
• Weekend and holiday blackouts are common, especially around major holidays.
• Rush-hour and urban curfews keep big loads out of metro areas at peak times.
• Overweight-only loads within legal dimensions can often travel continuously.

6When it becomes a superload

Past a certain size, an oversize load crosses into superload territory — the biggest tier, with route surveys, engineering review, bridge analysis, and lead times measured in weeks instead of days. If your load is extremely wide, tall, long, or heavy, read the Superload 101 guide next.