What the Freight Index Measures

Every supply chain leader eventually runs into the same disconnect: their own freight costs are moving in a direction their budget didn't predict, and they want to know whether it's their carriers, their network, or the market. That's exactly the question a freight index is built to answer. It separates what's happening broadly across the industry from what's happening specifically inside one company's shipping data, and reading it correctly changes how a leader interprets their own numbers.

Key takeaways:

A freight index tracks aggregate volume and spend trends across the freight market, not any single company's costs
The most widely cited benchmark, the Cass Freight Index, is built from 35 million commercial invoices and $37 billion in annual freight spend
Shipments and expenditures are tracked as separate components, and they don't always move together
Linehaul rate indices strip out fuel and accessorial charges to isolate pure pricing trends
The real value of an index is context, telling a leader whether their own cost movement is market-driven or company-specific

What a freight index is

A freight index is a standardized measure of freight market activity over time, built from real transaction data rather than surveys or estimates. The most established one, the Cass Freight Index, has tracked North American freight activity since 1995 and draws on 35 million commercial invoices and $37 billion in freight spend processed annually across a client base spanning consumer packaged goods, food, automotive, chemical, medical, retail, and heavy equipment shippers. Because it's built from actual paid invoices rather than sentiment surveys, it reflects what companies genuinely spent and shipped, not what the market expected them to.

The index uses a fixed base period, January 1990, and every subsequent reading is expressed relative to that starting point. That structure lets analysts compare freight activity across decades on a consistent scale, which is part of why the index gets cited so widely in economic reporting well beyond logistics circles.

The two components that matter, and why they don't always agree

A freight index isn't one number. It's built from at least two distinct components that measure different things and frequently diverge. The shipments component tracks the volume of freight moving, the actual count of loads across truckload, less-than-truckload, and other domestic modes, with truckload typically accounting for more than half of shipments and LTL around a quarter. The expenditures component tracks total dollars spent on freight transportation, covering both contract and spot market rates.

These two numbers telling different stories is normal, and it's often the most useful signal in the whole index. When shipments fall while expenditures rise, the market is telling you rates are climbing faster than volume is shrinking, meaning capacity is tight enough that fewer loads still cost more in aggregate. That's precisely the pattern that's shown up through parts of 2026, with shipment volumes down year over year in the first quarter while expenditures rose, a combination that points to tightening capacity rather than a demand-side rebound.

Linehaul indices isolate the piece everything else obscures

Total freight spend includes fuel surcharges and accessorial charges layered on top of the base transportation cost, and those additions can move independently of what carriers are actually charging to move a load from one point to another. This is why a separate linehaul index exists. The Cass Truckload Linehaul Index measures market fluctuations in per-mile truckload rates specifically, independent of fuel and accessorials, giving analysts and shippers a cleaner read on where core pricing is actually headed.

That distinction matters more in periods like the current one, where reefer accessorial charges have been climbing and fuel costs are volatile enough to distort a blended number. A shipper looking only at total spend might conclude rates are surging when a meaningful share of that increase is coming from accessorial and fuel pressure rather than the linehaul rate itself. Separating the two components is the difference between diagnosing a real base rate shift and reacting to noise.

What supply chain leaders should watch, and how to use it

The index itself isn't a decision-making tool on its own. Its value is comparative: does what's happening in a company's own freight costs match what the broader market is doing, or is something specific to that company's network, carrier mix, or contracts driving the difference. If a company's linehaul costs are rising faster than the published index, that's a signal worth investigating at the carrier or lane level rather than assuming it's simply "the market." If costs are rising in line with the index, that's evidence the pressure is systemic and the better response is strategic, adjusting contract structure or capacity commitments, not renegotiating with a single carrier who's simply pricing to the same conditions everyone else is.

Supply chain and procurement leaders should also pay attention to the direction of divergence between shipments and expenditures over consecutive months, not just a single reading. A one-month anomaly can be seasonal. A multi-month trend where shipments keep falling while expenditures keep climbing is a capacity story playing out in real time, and it's usually a better early warning than waiting for next quarter's freight budget variance to show it.

Why this matters for budgeting, not just market awareness

The practical payoff of understanding a freight index shows up at budget time. A finance or procurement team that can point to published shipment and expenditure trends has a much stronger basis for revising a freight budget mid-year than one relying purely on last year's contract terms. It also strengthens carrier negotiations, since a team that understands whether current rate pressure is company-specific or market-wide walks into that conversation with a clearer sense of what's actually negotiable.

None of this replaces a company's own transportation spend data, though. A macro index tells a supply chain leader what the market as a whole is doing. It doesn't show which of their own carriers, lanes, or shipment types are driving their specific cost trend, and that's the layer that determines what to actually do about it. Reading the index alongside a company's own normalized freight and invoice data, the kind Trax's Market Intelligence and analytics tools are built to surface, is what turns a general market signal into a specific, actionable answer about where a company's own spend is headed and why.

The takeaway for anyone budgeting or negotiating freight this year

A freight index is a benchmark, not a forecast, and it's most useful as a reality check against a company's own numbers rather than a replacement for them. Supply chain leaders who track both the shipments and expenditures components, separate linehaul movement from fuel and accessorial noise, and compare all of it against their own company-specific data are the ones who catch market shifts early enough to actually act on them, instead of discovering the shift for the first time in a quarterly invoice review.