Rail basics

Class I Railroads (BNSF, UP, CSX, NS, CPKC, CN): A Shipper's Map

Published June 3, 2026

Six Class I railroads carry roughly 94% of US rail freight by ton-miles: BNSF (Burlington Northern Santa Fe), Union Pacific (UP), CSX, Norfolk Southern (NS), CPKC (Canadian Pacific Kansas City), and Canadian National (CN). Each runs a different region, prices differently, and tends to overbill in different places. If you ship rail in the US, this is the map you need before reading a freight invoice. Your first audit with Eller Audit is free.

What makes a railroad “Class I”

The Class I label is not marketing. It is a Surface Transportation Board revenue threshold codified at 49 CFR 1201, updated annually for inflation. For 2024 reporting, the threshold sits at $1.04 billion in annual operating revenue. Cross the line for three consecutive years and you are Class I, with the reporting obligations that come with it — quarterly R-1 filings, public tariff publication, and STB jurisdiction over certain rate disputes.

The Interstate Commerce Commission (ICC) created the three-tier classification in 1911 to scale reporting requirements to carrier size. At the time there were 71 Class I railroads. A century of mergers, bankruptcies, and abandonments compressed that count to six. The Penn Central collapse, Conrail's creation and breakup, the Burlington Northern / Santa Fe merger, the Union Pacific / Southern Pacific merger, and most recently the 2023 CPKC merger each redrew the map. What is left is a tight oligopoly: two western carriers, two eastern carriers, and two cross-border carriers, with very little geographic overlap.

For a shipper, the practical implication is simple. On most lanes you have one realistic Class I option, occasionally two. Bid season is less about playing carriers against each other and more about reading each carrier's tariff structure carefully enough to negotiate the lines that matter.

The six US Class I railroads, profiled

BNSF (Burlington Northern Santa Fe)

Headquartered in Fort Worth, TX. ~32,500 route miles across 28 western states. Largest US rail network by route miles. Primary commodities: intermodal (Pacific Coast import containers eastbound), coal from the Powder River Basin, agricultural products, and consumer goods. Owned by Berkshire Hathaway since 2010.

Billing pattern worth knowing: BNSF publishes fuel surcharges against the US Department of Energy (DOE) Highway Diesel Fuel (HDF) West region index, updated weekly. When a contract references “DOE diesel” without specifying West, BNSF defaults to the West reading even on shipments that originate or terminate in the Midwest. The math is small per car but compounds across thousands of moves.

Union Pacific (UP)

Headquartered in Omaha, NE. ~32,200 route miles across 23 western states. Effectively co-equal with BNSF on the western map — the two carriers run parallel networks with different strengths. UP has the I-5 corridor advantage in California and stronger Gulf Coast petrochemical access through the former Southern Pacific lines.

Billing pattern worth knowing: UP fuel surcharges use a DOE HDF national average plus a UP-specific supplement published quarterly. The supplement adjusts for regional diesel-price divergence and is the line most often missed during audit because the surcharge formula on the bill rarely shows the supplement separately. You have to read the published fuel program against the invoice.

CSX

Headquartered in Jacksonville, FL. ~19,500 route miles across 23 eastern states and parts of Canada. The dominant southeastern coastal carrier, with heavy intermodal volume from East Coast ports (Savannah, Charleston, Norfolk, NY/NJ) to inland Midwest hubs and a meaningful Appalachian coal franchise.

Billing pattern worth knowing: CSX uses the DOE HDF East region index for fuel and updates linehaul tariffs on a quarterly cycle, typically the first business day of January, April, July, and October. The most common overbilling we see on CSX is stale-rate billing in the first two weeks after a tariff change — cars tendered on the new rate effective date but billed against last quarter's table.

Norfolk Southern (NS)

Headquartered in Atlanta, GA. ~19,200 route miles across 22 eastern states and Washington, DC. Direct competitor to CSX on most eastern lanes, with stronger interior coal and automotive franchises and a deeper intermodal network into Pennsylvania and Ohio.

Billing pattern worth knowing: NS also publishes against the DOE HDF East region index, but its accessorial schedule — switching, weighing, reconsignment — updates on a semi-annual cycle rather than CSX's quarterly cadence. A shipper with parallel CSX and NS contracts has to track two different update calendars to keep accounts payable (AP) from paying stale accessorials on the NS side.

CPKC (Canadian Pacific Kansas City)

Co-headquartered in Calgary, AB and Kansas City, MO. ~20,000 route miles across Canada, the US Midwest, and Mexico. Formed April 2023 by the merger of Canadian Pacific and Kansas City Southern — the first and so far only single-line railroad connecting all three USMCA countries. Primary commodities: grain, intermodal, automotive, petrochemicals, and Mexican cross-border manufactured goods.

Billing pattern worth knowing: Post-merger, CPKC is still harmonizing the legacy CP and KCS tariff structures. As of mid-2026, some lanes still bill against pre-merger KCS rates with a conversion factor, and pre-merger CP fuel programs still apply on the Canadian-origin side. Audit discipline on CPKC requires knowing which legacy tariff governs each lane — the wrong rate table is the most common error.

Canadian National (CN)

Headquartered in Montreal, QC. ~18,500 route miles across Canada and the US Midwest, with a unique Canada-to-Gulf-Coast corridor through Chicago, Memphis, and New Orleans (the former Illinois Central). Primary commodities: intermodal, forest products, grain, petroleum and chemicals, and metals.

Billing pattern worth knowing: CN tariffs differentiate between US-domestic, US-Canada cross-border, and Canada-domestic pricing structures, and each has a different fuel surcharge basis (DOE HDF for US-origin moves, a Canadian National Energy Board diesel index for Canada-domestic). Cross-border shipments tendered on a US-origin Bill of Lading (BOL) but delivered in Canada are the line most often misbilled — the wrong fuel program gets applied at the border.

How tariff structures differ across Class I rails

All six Class I railroads publish public tariffs. They are not all published the same way, and they do not change on the same schedule. The practical effect for a shipper: a master contract that references “the carrier's published tariff” means six different things, and the audit has to read each one against the contract on its own terms.

Update cadence. CSX and BNSF run roughly quarterly linehaul tariff cycles, with effective dates tied to the first business day of each quarter. UP runs a quarterly cycle but issues mid-quarter supplements for specific commodity groups. NS updates linehaul quarterly but accessorials semi-annually. CPKC, still post-merger, runs two parallel update calendars — the legacy CP cycle and the legacy KCS cycle — that have not yet fully merged. CN updates US-domestic tariffs quarterly and Canada-domestic tariffs on a separate calendar driven by the Canadian Transportation Agency review cycle.

Fuel surcharge index. The DOE HDF index is the standard, but the regional subset matters. BNSF defaults to West, CSX and NS to East, UP to national plus supplement, CPKC to legacy CP and KCS programs being slowly unified, and CN to a US/Canada split. A contract that just says “DOE diesel” lets the carrier pick the regional reading. Pin the subset in the contract.

Demurrage tariff. All six publish demurrage tariffs that define free time, daily rates, and constructive-placement notification requirements. The tariffs are typically updated annually, but free-time allowances and per-day rates vary — a Class I demurrage tariff issued in January 2026 might allow 24 hours of free time on a hopper car at a private siding while another allows 48 hours on the same car type. The contract may override the free-time allowance, but rarely overrides the notification mechanics.

Class I comparison at a glance

Railroad	HQ	Route miles (approx)	Primary region	Fuel surcharge basis	Demurrage tariff cycle
BNSF	Fort Worth, TX	32,500	Western US	DOE HDF West, weekly	Annual
Union Pacific (UP)	Omaha, NE	32,200	Western US	DOE HDF national + UP supplement	Annual
CSX	Jacksonville, FL	19,500	Eastern US	DOE HDF East, weekly	Annual
Norfolk Southern (NS)	Atlanta, GA	19,200	Eastern US	DOE HDF East, weekly	Annual (accessorials semi-annual)
CPKC	Calgary / Kansas City	20,000	US Midwest + Canada + Mexico	Legacy CP and KCS programs, unifying	Annual, dual-track post-merger
Canadian National (CN)	Montreal, QC	18,500	US Midwest + Canada (East-West-Gulf)	DOE HDF (US) / NEB diesel (Canada)	Annual

Class II and Class III: regional and short-line carriers

The six Class I rails get the headlines, but most US rail shipments touch a Class II or Class III carrier somewhere — usually on the first mile or last mile, between a private siding and the Class I interchange point. There are roughly 20 Class II regional railroads and 600 Class III short-line railroads in the US.

For shippers, Class II and Class III carriers typically appear as a separate switch charge or drayage line on the same waybill or freight invoice, or as a separately-billed short-line haul with its own waybill that interchanges to a Class I carrier. The controlling tariff is the short-line's own, which is usually shorter, less frequently updated, and often hand-quoted on a per-move basis.

The disclaimer worth stating up front: short-line tariff complexity is real. A short-line that primarily moves loaded hopper cars from one plant to a Class I interchange may have a tariff that is six pages long and covers ten commodity codes. A short-line that handles a more diverse mix may have a tariff that runs longer and is revised annually with handshake amendments in between. The audit logic is the same as for a Class I — read the controlling document next to the bill — but the tariff library is more fragmented and the change history is less public.

What we can't tell from the bill alone

A Class I rail freight bill is incomplete on its own. The carrier's bill is the application of two documents — the published tariff and the private contract — and the contract usually overrides parts of the tariff while leaving the rest in effect. A bill that looks correct against the tariff may be wrong against the contract. A bill that looks wrong against the tariff may be exactly right under a contract override. Without both documents in hand at the same time, you cannot tell.

The contract override is most common on linehaul rate (most shippers negotiate a discount off the tariff base) and on fuel surcharge program (most negotiate a different strike price or index region). It is less common on demurrage mechanics, switching authority, and accessorial charges, where the tariff usually still controls. The rule of thumb: the line items that move the most money are negotiated; the line items that produce the most disputes are not.

An audit reads both documents as one. AP usually cannot, because AP sees the invoice and a rate table, not the full contract and the full tariff together. That gap is where Class I overcharges live — industry estimates put rail-specific invoice error rates at 5 to 8 percent of total billed spend, the higher end of the freight audit range.

How Eller Audit handles Class I rail

We keep a current tariff library for all six Class I railroads — BNSF, UP, CSX, NS, CPKC, and CN — refreshed against each carrier's published update cycle, and paired with the controlling contract for each shipper. Every waybill or freight invoice runs against both documents, with a human auditor reviewing any line where the variance crosses the threshold. The engagement is performance-based: you pay a share of what we recover and nothing on the lines that hold up. Most rail disputes resolve inside the carrier's 60–90 day claims window, and we keep your AP team out of the back-and-forth so the carrier relationship stays clean.

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