# Houston freight accessorial charges to watch > Houston freight bills carry accessorials tied to port drayage and fuel indices. Here is what to check against contract terms, with sourced rate data. Source: https://valuexpa.com/insights/houston-freight-accessorial-charges-to-watch Publisher: ValueXPA (https://valuexpa.com) Updated: 2026-09-06 --- Margin drift is the gap between what a vendor contract says and what the invoice actually charges. In Houston freight, that gap shows up fastest in accessorial lines: detention at the port, chassis fees, fuel surcharges, and tanker wash charges that ride alongside the base linehaul rate. Houston's freight profile is not generic trucking. It combines container drayage out of the Port of Houston, petrochemical and refinery tank truck movements along the Ship Channel, and long-haul TL lanes running toward the Permian Basin and along I-10. Each lane carries its own accessorial exposure, and each one moves against a national cost index that a Houston shipper's contract should reference by name. ## Executive Summary Freight cost indices moved sharply through mid-2026, and Houston's lane mix means the increases land unevenly across accessorial categories rather than the base rate alone. The Producer Price Index for truck transportation of freight (BLS series WPU3012) stood at 170.984 in July 2026, up 10.9% year over year, read September 6, 2026. The long-distance TL trucking industry index (PCU484121484121) reached 195.575, up 8.1% year over year, same read date. Gasoline PPI (WPU0571) rose 37.1% year over year to 302.759, also read September 6, 2026. The mechanism that turns index movement into invoice drift is the surcharge table. A fuel surcharge schedule that references a stale baseline, or a detention clause written before current port gate patterns, keeps charging its own formula while the underlying cost moves independently. Houston's port drayage and Ship Channel tanker traffic add accessorial categories, chassis rental, wash-out fees, terminal wait time, that a lane without a port or a chemical corridor never bills at all. What changes this is checking each accessorial line against the index it claims to track, and against the specific gate, terminal, or chassis pool named in the carrier agreement, rather than accepting the line item on trust because the shipment did in fact move. ## 1. What is different about freight billing in Houston? **Houston freight billing differs because three distinct freight systems overlap in one metro: container drayage through the Port of Houston, petrochemical tank truck movement along the Ship Channel, and long-haul truckload lanes serving the Permian Basin and the I-10 corridor. Each system bills its own accessorial set, chassis and wharfage fees for drayage, wash-out and hazmat handling for tank trucks, detention and layover for long-haul, so a single Houston-based carrier agreement often needs three separate accessorial schedules instead of one.** A shipper outside a port market negotiates a fuel surcharge and a detention clause and is largely done. A Houston shipper negotiating the same categories has to specify which move they apply to, because a container drayage detention clock starts differently from a dry van detention clock, and a tank truck wash ticket is not billed the same way as a dry freight cleaning fee. The practical effect is that a single master agreement covering multiple Houston lane types often carries accessorial definitions that were written for one lane and get applied, incorrectly, to another. A drayage detention rate gets billed on a long-haul move, or a wash-out charge appears on a load that never touched a tank. This is the audit point specific to Houston: check which accessorial schedule the invoice actually drew from, and whether that schedule matches the equipment type and lane on the bill of lading, not just the carrier name. ## 2. How do port drayage accessorials differ from long-haul accessorials? **Port drayage accessorials are billed against the container and the terminal, not the truck. Chassis rental, per diem, and terminal wait time all key off the container's dwell time at the Port of Houston, independent of how long the truck itself was in use. Long-haul accessorials, by contrast, key off the truck and driver: detention starts at the shipper's dock, layover applies to the tractor, and neither concept transfers cleanly to a container move.** A drayage invoice typically separates the chassis line from the drayage line from the per diem line, because each is billed by a different party in the container's chain of custody: the chassis pool operator, the ocean carrier, and the drayage trucking company. This matters for the audit because the three lines can each carry their own free-time clock, and a delay anywhere in that chain, a slow terminal gate, a chassis shortage, a late release, can generate a charge that has nothing to do with the trucking company's own performance. A long-haul TL accessorial schedule has none of this structure. Detention is a single clock starting at arrival, and layover is a single daily rate. Applying a drayage-style multi-party accessorial review to a long-haul invoice, or vice versa, means checking the wrong clock against the wrong charge. ### A. Chassis and per diem Chassis rental is billed by the chassis pool provider, often a party the trucking company does not control, and per diem is billed by the ocean carrier for container dwell beyond the free period. Both can appear on the drayage invoice as pass-through charges. The audit question is whether the pass-through rate matches the pool provider's or carrier's own published tariff, not the trucking company's rate card, since the trucking company has no pricing authority over either line. ### B. Terminal wait time Wait time at a Port of Houston terminal gate is billed against the truck's time in the queue, which the trucking company logs itself. Unlike detention at a shipper's dock, there is no independent third-party clock unless the terminal operator's own gate transaction data is checked against the invoiced hours. ## 3. Why does the fuel surcharge line need extra scrutiny on Houston lanes? **Gasoline PPI (BLS series WPU0571) rose 37.1% year over year to 302.759 in July 2026, read September 6, 2026, a sharper move than the general truck transportation index. A fuel surcharge table pegged to a stale baseline or an infrequently updated index understates or overstates the current charge, and on Houston's refinery-adjacent lanes, where tank truck fuel consumption per mile runs against the same volatile input costs, the gap between the contracted formula and the current cost compounds.** A fuel surcharge clause typically names a reference index and a baseline price. The audit step is confirming the invoice's surcharge was calculated against that named index at the current published value, not against an internal carrier estimate that moves on its own schedule. Because gasoline PPI moved 37.1% year over year while the general truck transportation PPI (WPU3012) moved 10.9% over the same period, a surcharge formula tied loosely to "fuel costs" rather than to a named, dated index reading can drift substantially from either figure depending on which one the carrier actually used. This is not a Houston-specific mechanism on its own. What is specific to Houston is the volume of tank truck and drayage traffic where fuel is a larger share of the per-mile cost than on a typical dry van long-haul lane, which means the dollar impact of an uncorrected surcharge formula compounds faster here than on a lane with lower fuel intensity. ## 4. How does Ship Channel tank truck traffic change accessorial exposure? **Ship Channel tank truck movements bill accessorial categories that a dry freight audit never encounters: wash-out charges between incompatible product loads, hazmat handling fees, and tank certification surcharges. Each has its own documentation requirement, a wash ticket, a hazmat manifest, a certification date, and each can be invoiced without that documentation attached, which is the specific gap a Houston-area invoice audit has to close that a general freight audit does not.** A tank truck moving between petrochemical facilities along the Ship Channel is billed a wash-out fee whenever the next load requires a different tank condition than the last. That fee should carry a wash ticket showing the facility, the date, and the product transition. Hazmat handling and tank certification surcharges follow a similar pattern: they are legitimate charges when the underlying work happened, and they are drift when billed by default on every load regardless of whether wash-out, hazmat handling, or recertification actually occurred. The audit question for this category is documentation-first: does every wash-out, hazmat, or certification line have a corresponding ticket, and does the ticket date align with the load it is billed against. Long-haul dry freight invoices carry no equivalent category, so a Houston-only checklist has to add this line explicitly rather than inheriting a generic freight audit template. ## 5. Which contract clauses should a Houston shipper check first? **Three clauses carry the most Houston-specific exposure: the fuel surcharge index reference, the detention or per diem free-time definition by lane type, and the accessorial schedule's equipment scope. Each should name the specific index, terminal, or equipment type it applies to rather than using a single blanket definition across drayage, tank truck, and long-haul moves that a multi-modal Houston carrier agreement typically covers under one master contract.** A fuel surcharge clause should name the index, WPU0571 or an equivalent published series, the baseline reading date, and the update frequency. A clause that says "adjusted for fuel costs" without naming a source gives the carrier discretion the shipper cannot audit against. Detention and per diem definitions need to specify which move type they govern. A single "detention: 2 hours free, $75/hour thereafter" clause applied uniformly across drayage, tank truck, and dry van moves will systematically misprice at least two of the three, since drayage per diem and tank truck wash-out timing follow entirely different clocks. The accessorial schedule's equipment scope should list which charges apply to which equipment type explicitly, chassis and per diem for containers, wash-out and hazmat for tank trucks, layover and detention for dry van and flatbed, so an invoice line can be checked against a named clause rather than a general accessorial category. - **Fuel surcharge index reference:** Name the published index and baseline date. A vague reference to fuel costs cannot be audited. - **Detention and per diem clocks:** Specify a separate free-time definition for each equipment type moved under the agreement. - **Equipment-scoped accessorial list:** List which charges apply to which equipment type, so a line item can be checked against a named clause. ## 6. How should a Houston-based manufacturer approach this audit? **Start by separating invoices by move type, drayage, tank truck, and long-haul, before checking any accessorial line, since the correct reference clause and documentation requirement differ by move type even within a single carrier's invoices. Then check each fuel surcharge line against its named index and baseline, and each specialty accessorial, wash-out, hazmat, chassis per diem, against its supporting ticket. This sequence catches the misapplied-clause and missing-documentation drift specific to a multi-modal Houston freight book.** Sorting by move type first matters because a single master carrier agreement covering all three Houston lane types will contain three sets of definitions, and an invoice line checked against the wrong set will look compliant when it is not, or look wrong when it is actually correct under its own applicable clause. After sorting, the fuel surcharge check and the documentation check are the two highest-value passes, because both fail silently: a stale surcharge index and a missing wash ticket both produce an invoice that looks routine and processes without exception. A broader diagnostic across a full indirect spend base would place this work inside a wider [freight and 3PL audit](/answers/how-do-you-audit-freight-and-3pl-invoices) and cross-check it against the general PPI trend, since accessorial-level review only makes sense in the context of the base rate it sits alongside. For the wider pattern this sits inside, start with the [margin drift](/guides/indirect-spend-audit-categories) guide. See also [the six categories drift hides in](/guides/indirect-spend-audit-categories) and [accessorial charge audit: the surcharges nobody validates](/guides/accessorial-charge-audit-the-surcharges-nobody-validates). ## 7. Frequently Asked Questions (People Also Ask) ### What index should a Houston fuel surcharge clause reference? The clause should name a specific published series, such as BLS PPI WPU0571 for gasoline, with a baseline reading date and an update frequency. Without a named index, the carrier can apply its own internal fuel adjustment, which cannot be independently checked against public data. ### Why do drayage and long-haul detention clocks differ? Drayage detention and per diem apply to the container and start at the terminal or the chassis pool, tracked by the ocean carrier or pool operator. Long-haul detention applies to the truck and starts at the shipper's dock. Using one clause to cover both means at least one move type is priced against the wrong clock. ### What documentation should back a Ship Channel wash-out charge? A wash-out charge should carry a wash ticket naming the facility, the date, and the product transition that required the wash. A wash-out line with no ticket attached, or a ticket date that does not match the load date, is a documentation gap worth flagging. ### Does Houston freight cost more than other US markets right now? The proof registry here does not include a Houston-specific cost index, only national series. BLS PPI for truck transportation of freight (WPU3012) rose 10.9% year over year to 170.984 in July 2026, read September 6, 2026, and that national trend is the reference point available for comparison. ### Is a chassis rental fee the trucking company's own charge? No. Chassis rental is typically billed by a separate chassis pool provider and passed through on the drayage invoice. The audit question is whether the pass-through rate matches the pool provider's own published tariff, since the trucking company usually has no pricing authority over that line. ### How often should a Houston shipper re-check its fuel surcharge formula? The contract should specify an update frequency tied to the named index's own publication schedule. BLS PPI series update monthly, so a surcharge formula referencing one of them should recalculate on the same monthly cadence rather than an arbitrary quarterly or annual review. ### Can a single carrier agreement cover drayage, tank truck, and long-haul moves? Yes, and many Houston-area agreements do, but each move type needs its own accessorial and free-time definitions within that agreement. A single blanket definition applied across all three move types is the most common source of misapplied charges in a multi-modal Houston freight book. ### What is a wash-out charge? A wash-out charge covers cleaning a tank truck's interior between loads when the next product requires a different tank condition than the last. It is a legitimate charge when the wash occurred and should be supported by a wash ticket showing the facility, date, and product transition. ### Is contract complexity quietly draining your operating margin? A small systematic drift between your negotiated contracts and your actual vendor billing compounds quietly across a year of invoices. Stop guessing at your exposure and run a targeted audit. **[Take the Free Screener → https://valuexpa.com/margin-drift-screener](https://valuexpa.com/margin-drift-screener)** ## Executive Summary Freight cost indices moved sharply through mid-2026, and Houston's lane mix means the increases land unevenly across accessorial categories rather than the base rate alone. The Producer Price Index for truck transportation of freight (BLS series WPU3012) stood at 170.984 in July 2026, up 10.9% year over year, read September 6, 2026. The long-distance TL trucking industry index (PCU484121484121) reached 195.575, up 8.1% year over year, same read date. Gasoline PPI (WPU0571) rose 37.1% year over year to 302.759, also read September 6, 2026. The mechanism that turns index movement into invoice drift is the surcharge table. A fuel surcharge schedule that references a stale baseline, or a detention clause written before current port gate patterns, keeps charging its own formula while the underlying cost moves independently. Houston's port drayage and Ship Channel tanker traffic add accessorial categories, chassis rental, wash-out fees, terminal wait time, that a lane without a port or a chemical corridor never bills at all. What changes this is checking each accessorial line against the index it claims to track, and against the specific gate, terminal, or chassis pool named in the carrier agreement, rather than accepting the line item on trust because the shipment did in fact move. ## 1. What is different about freight billing in Houston? Houston freight billing differs because three distinct freight systems overlap in one metro: container drayage through the Port of Houston, petrochemical tank truck movement along the Ship Channel, and long-haul truckload lanes serving the Permian Basin and the I-10 corridor. Each system bills its own accessorial set, chassis and wharfage fees for drayage, wash-out and hazmat handling for tank trucks, detention and layover for long-haul, so a single Houston-based carrier agreement often needs three separate accessorial schedules instead of one. A shipper outside a port market negotiates a fuel surcharge and a detention clause and is largely done. A Houston shipper negotiating the same categories has to specify which move they apply to, because a container drayage detention clock starts differently from a dry van detention clock, and a tank truck wash ticket is not billed the same way as a dry freight cleaning fee. The practical effect is that a single master agreement covering multiple Houston lane types often carries accessorial definitions that were written for one lane and get applied, incorrectly, to another. A drayage detention rate gets billed on a long-haul move, or a wash-out charge appears on a load that never touched a tank. This is the audit point specific to Houston: check which accessorial schedule the invoice actually drew from, and whether that schedule matches the equipment type and lane on the bill of lading, not just the carrier name. ## 2. How do port drayage accessorials differ from long-haul accessorials? Port drayage accessorials are billed against the container and the terminal, not the truck. Chassis rental, per diem, and terminal wait time all key off the container's dwell time at the Port of Houston, independent of how long the truck itself was in use. Long-haul accessorials, by contrast, key off the truck and driver: detention starts at the shipper's dock, layover applies to the tractor, and neither concept transfers cleanly to a container move. A drayage invoice typically separates the chassis line from the drayage line from the per diem line, because each is billed by a different party in the container's chain of custody: the chassis pool operator, the ocean carrier, and the drayage trucking company. This matters for the audit because the three lines can each carry their own free-time clock, and a delay anywhere in that chain, a slow terminal gate, a chassis shortage, a late release, can generate a charge that has nothing to do with the trucking company's own performance. A long-haul TL accessorial schedule has none of this structure. Detention is a single clock starting at arrival, and layover is a single daily rate. Applying a drayage-style multi-party accessorial review to a long-haul invoice, or vice versa, means checking the wrong clock against the wrong charge. ### A. Chassis and per diem Chassis rental is billed by the chassis pool provider, often a party the trucking company does not control, and per diem is billed by the ocean carrier for container dwell beyond the free period. Both can appear on the drayage invoice as pass-through charges. The audit question is whether the pass-through rate matches the pool provider's or carrier's own published tariff, not the trucking company's rate card, since the trucking company has no pricing authority over either line. ### B. Terminal wait time Wait time at a Port of Houston terminal gate is billed against the truck's time in the queue, which the trucking company logs itself. Unlike detention at a shipper's dock, there is no independent third-party clock unless the terminal operator's own gate transaction data is checked against the invoiced hours. ## 3. Why does the fuel surcharge line need extra scrutiny on Houston lanes? Gasoline PPI (BLS series WPU0571) rose 37.1% year over year to 302.759 in July 2026, read September 6, 2026, a sharper move than the general truck transportation index. A fuel surcharge table pegged to a stale baseline or an infrequently updated index understates or overstates the current charge, and on Houston's refinery-adjacent lanes, where tank truck fuel consumption per mile runs against the same volatile input costs, the gap between the contracted formula and the current cost compounds. A fuel surcharge clause typically names a reference index and a baseline price. The audit step is confirming the invoice's surcharge was calculated against that named index at the current published value, not against an internal carrier estimate that moves on its own schedule. Because gasoline PPI moved 37.1% year over year while the general truck transportation PPI (WPU3012) moved 10.9% over the same period, a surcharge formula tied loosely to "fuel costs" rather than to a named, dated index reading can drift substantially from either figure depending on which one the carrier actually used. This is not a Houston-specific mechanism on its own. What is specific to Houston is the volume of tank truck and drayage traffic where fuel is a larger share of the per-mile cost than on a typical dry van long-haul lane, which means the dollar impact of an uncorrected surcharge formula compounds faster here than on a lane with lower fuel intensity. ## 4. How does Ship Channel tank truck traffic change accessorial exposure? Ship Channel tank truck movements bill accessorial categories that a dry freight audit never encounters: wash-out charges between incompatible product loads, hazmat handling fees, and tank certification surcharges. Each has its own documentation requirement, a wash ticket, a hazmat manifest, a certification date, and each can be invoiced without that documentation attached, which is the specific gap a Houston-area invoice audit has to close that a general freight audit does not. A tank truck moving between petrochemical facilities along the Ship Channel is billed a wash-out fee whenever the next load requires a different tank condition than the last. That fee should carry a wash ticket showing the facility, the date, and the product transition. Hazmat handling and tank certification surcharges follow a similar pattern: they are legitimate charges when the underlying work happened, and they are drift when billed by default on every load regardless of whether wash-out, hazmat handling, or recertification actually occurred. The audit question for this category is documentation-first: does every wash-out, hazmat, or certification line have a corresponding ticket, and does the ticket date align with the load it is billed against. Long-haul dry freight invoices carry no equivalent category, so a Houston-only checklist has to add this line explicitly rather than inheriting a generic freight audit template. ## 5. Which contract clauses should a Houston shipper check first? Three clauses carry the most Houston-specific exposure: the fuel surcharge index reference, the detention or per diem free-time definition by lane type, and the accessorial schedule's equipment scope. Each should name the specific index, terminal, or equipment type it applies to rather than using a single blanket definition across drayage, tank truck, and long-haul moves that a multi-modal Houston carrier agreement typically covers under one master contract. A fuel surcharge clause should name the index, WPU0571 or an equivalent published series, the baseline reading date, and the update frequency. A clause that says "adjusted for fuel costs" without naming a source gives the carrier discretion the shipper cannot audit against. Detention and per diem definitions need to specify which move type they govern. A single "detention: 2 hours free, $75/hour thereafter" clause applied uniformly across drayage, tank truck, and dry van moves will systematically misprice at least two of the three, since drayage per diem and tank truck wash-out timing follow entirely different clocks. The accessorial schedule's equipment scope should list which charges apply to which equipment type explicitly, chassis and per diem for containers, wash-out and hazmat for tank trucks, layover and detention for dry van and flatbed, so an invoice line can be checked against a named clause rather than a general accessorial category. - Fuel surcharge index reference: Name the published index and baseline date. A vague reference to fuel costs cannot be audited. - Detention and per diem clocks: Specify a separate free-time definition for each equipment type moved under the agreement. - Equipment-scoped accessorial list: List which charges apply to which equipment type, so a line item can be checked against a named clause. ## 6. How should a Houston-based manufacturer approach this audit? Start by separating invoices by move type, drayage, tank truck, and long-haul, before checking any accessorial line, since the correct reference clause and documentation requirement differ by move type even within a single carrier's invoices. Then check each fuel surcharge line against its named index and baseline, and each specialty accessorial, wash-out, hazmat, chassis per diem, against its supporting ticket. This sequence catches the misapplied-clause and missing-documentation drift specific to a multi-modal Houston freight book. Sorting by move type first matters because a single master carrier agreement covering all three Houston lane types will contain three sets of definitions, and an invoice line checked against the wrong set will look compliant when it is not, or look wrong when it is actually correct under its own applicable clause. After sorting, the fuel surcharge check and the documentation check are the two highest-value passes, because both fail silently: a stale surcharge index and a missing wash ticket both produce an invoice that looks routine and processes without exception. A broader diagnostic across a full indirect spend base would place this work inside a wider [freight and 3PL audit](/answers/how-do-you-audit-freight-and-3pl-invoices) and cross-check it against the general PPI trend, since accessorial-level review only makes sense in the context of the base rate it sits alongside. For the wider pattern this sits inside, start with the [margin drift](/guides/indirect-spend-audit-categories) guide. See also [the six categories drift hides in](/guides/indirect-spend-audit-categories) and [accessorial charge audit: the surcharges nobody validates](/guides/accessorial-charge-audit-the-surcharges-nobody-validates). ## Common questions ### What index should a Houston fuel surcharge clause reference? The clause should name a specific published series, such as BLS PPI WPU0571 for gasoline, with a baseline reading date and an update frequency. Without a named index, the carrier can apply its own internal fuel adjustment, which cannot be independently checked against public data. ### Why do drayage and long-haul detention clocks differ? Drayage detention and per diem apply to the container and start at the terminal or the chassis pool, tracked by the ocean carrier or pool operator. Long-haul detention applies to the truck and starts at the shipper's dock. Using one clause to cover both means at least one move type is priced against the wrong clock. ### What documentation should back a Ship Channel wash-out charge? A wash-out charge should carry a wash ticket naming the facility, the date, and the product transition that required the wash. A wash-out line with no ticket attached, or a ticket date that does not match the load date, is a documentation gap worth flagging. ### Does Houston freight cost more than other US markets right now? The proof registry here does not include a Houston-specific cost index, only national series. BLS PPI for truck transportation of freight (WPU3012) rose 10.9% year over year to 170.984 in July 2026, read September 6, 2026, and that national trend is the reference point available for comparison. ### Is a chassis rental fee the trucking company's own charge? No. Chassis rental is typically billed by a separate chassis pool provider and passed through on the drayage invoice. The audit question is whether the pass-through rate matches the pool provider's own published tariff, since the trucking company usually has no pricing authority over that line. --- ValueXPA runs a fixed-scope Margin Drift Diagnostic that validates every service vendor invoice against contract terms, for $100M+ US industrial manufacturers and distributors. Two to four weeks. The client retains 100% of recoveries. https://valuexpa.com/contact-us