01
Mexican carrier, plant to border
Picks up at origin and hauls the load to the border yard. This is where the Mexican standard, the federal and state permits, and the tax documentation of the domestic leg apply.
The shipment does not cross. It gets handed off, and that is where it drops.
A Mexico-to-U.S. crossing is not one continuous trip: it is a relay between different carriers, with two customs agencies and two permit regimes that do not recognize each other. Here is how it actually works, which document stops what, and what changes when the equipment is oversize.
The relay
Why the truck changes
Sheet 03 · Point 01
Why the shipment changes trucks at the border
The question shippers ask the most is why their load changes trucks at the border. The answer is that each carrier operates within its own authority, and neither one covers the full trip. So the move gets built as a relay.
02
Transfer, the short leg that crosses
A transfer or drayage carrier makes the physical crossing through customs. It is a trip of a few kilometers and it is the point where the customs broker files the pedimento and duties get covered. Short in distance, and still the link where most of the lost hours pile up.
03
U.S. carrier, to the destination
Takes the load on the American side and delivers it. From here on, U.S. rules govern, along with the permits of whichever state or states it passes through.
The two ways to build it
Transloading: the load moves from the Mexican trailer to the U.S. trailer at the border. Each carrier stays within its authority, and one more lift gets added. Through-trailer: the load stays in the same sealed trailer the whole way and only the tractor and driver change, which cuts handling and transit time. In project cargo the call is not about cost, it is about risk: every extra lift on a delicate piece is one more chance to damage it.
The documents
The ones that actually stop loads
Sheet 03 · Point 02
The documents that actually stop loads
A shipment does not get stopped for missing documents, it gets stopped for documents with one badly captured data point. These are the three that cause it most.
CFDI with Carta Porte supplement, version 3.1
Covers the domestic leg inside Mexico. Version 3.1 has been mandatory since July 17, 2024. For trucking it requires, among other things, the gross vehicle weight per NOM-012, the carrier's SICT permit number, its current insurance policy, and the data of the driver and the vehicle owner, plus precise origin and destination. It is the document that bounces the most, almost always over the declared weight or an over-captured vehicle configuration.
Pedimento
The official declaration of the operation, filed by the customs broker along with the tariff classification of the goods. A misassigned classification does not just cost money: it reopens the file and sends the unit back to the line.
ACE manifest
On the U.S. side, the carrier must transmit the manifest in the ACE system at least one hour before arriving at the border. Sounding obvious does not make it less common: a unit arriving without a transmitted manifest does not cross, and at a port like Laredo, where more than 17,000 trucks cross per day according to the city's 2026 report, losing your turn does not mean waiting minutes.
Oversize
Two countries, two regimes that do not match
Sheet 03 · Point 03
Oversize: two countries, two regimes that do not recognize each other
This is where a project cargo crossing stops looking like a normal one. The Mexican permit is worthless on the other side and the American one is worthless on this side. They are two filings, two calendars and two different definitions of what counts as oversize. The move gets planned as two moves that meet at one point, not as one.
Mexico, general maximum height (NOM-012-SCT-2-2017)4.25 m · 13 ft 11 in
Mexico, general maximum width2.60 m · 8 ft 6 in
Texas, width that requires escort on two-lane roads14 ft · 4.27 m
Texas, height that requires route survey and height-pole escort17 ft · 5.18 m
Texas, height that requires a certified route inspection18 ft 11 in · 5.77 m
Texas, lead time for TxDOT bridge and pavement analysis3 to 4 weeks
Published reference values. U.S. thresholds are set state by state and change from one state to the next, so a trip crossing three states can require three permits under three different criteria. Always confirm against the authority of the state involved before committing a date.
The number that reorders the schedule
Look at the comparison: in Mexico a 4.30-meter load is already over height, and in Texas that same load has not yet reached the threshold that triggers a route survey. The reverse happens just as often. That means the critical leg of an oversize crossing is not always on the side you assume, and planning the move with one country's criteria is the most common way to find out late.
Where it gets stuck
The four points, by frequency
Sheet 03 · Point 04
Where a crossing gets stuck, in order of frequency
Point 01
The carta porte data point
A gross vehicle weight that does not match the configuration, a wrong product code or an incomplete address. Fixed in minutes if someone is watching, and in a day if nobody flagged it.
Point 02
The relay with no owner
The load got handed to the transfer and the next carrier did not show, or showed with the wrong trailer. Nobody is lying: each one covered his leg and the gap fell between two of them.
Point 03
The permit on the other side
The move leaves Mexico fully compliant and the American state permit is not there, or arrived with a different route than the one planned. The equipment sits in a border yard collecting demurrage.
Point 04
The silence
The shipment got stuck on Thursday and the plant found out on Monday, when there was no way left to react. Of every point on this list, this is the only one that costs nothing to fix.
The first three get solved with a complete file and lead time. The fourth gets solved by someone following the shipment and picking up the phone the moment something leaves the plan, which is exactly what you hire when you hire coordination and not just a truck.
Questions
What gets asked about the crossing
Sheet 03 · Point 05
Frequently asked questions about the MX-USA crossing
Because each carrier operates within its own authority. The normal setup is a three-leg relay: the Mexican carrier to the border, the transfer carrier through customs, and the U.S. carrier to the destination. There is also through-trailer service, where the load is never touched and only the tractor and driver change.
On the Mexican side, the CFDI with the Carta Porte supplement for the domestic leg and the pedimento filed by the customs broker. On the American side, the ACE manifest transmitted at least one hour before arriving at the border.
Version 3.1, mandatory since July 17, 2024. For trucking it requires the gross vehicle weight per NOM-012, the carrier's SICT permit number, its current policy, and the data of the driver and the vehicle owner.
Yes, and they are separate regimes that do not recognize each other. In Mexico, NOM-012 and the federal, state and municipal permits apply, broken down on the permits sheet. In the United States it is state by state: in Texas, a load over 17 feet tall calls for a route survey and a height-pole escort, and TxDOT's bridge analysis takes three to four weeks of lead time.
The schedule is set by the slowest permit on either side, not by the transit. The installation date gets calculated backwards from there, which is why the route survey happens before committing a date.
Next sheets
Technical reference
Index
Next reference sheets
If you have a crossing coming up, let's review it before it moves.
Equipment, origin, destination and target date are enough to know which permits it calls for on both sides and how much lead time it needs. It comes inside the route survey, free.