Chart of the Week: Diesel Truck Stop Actual Price Per Gallon, National Truckload Index – USA SONAR: DTS.USA, NTI.USA
The average retail price of diesel (DTS) — the primary fuel source for Class 8 trucks — has risen over 41% since March 2. The average spot rate for dry van truckloads (NTI in orange) has increased 7.5% over the same stretch, forming a fairly strong positive correlation of 0.7, meaning they moved together fairly well. This is not always the case, however. In March 2022, the correlation was inverted at -0.8, meaning the two moved in opposite directions at nearly the same rate. This illustrates that fuel prices do not always drive truckload pricing movements. So what is the relationship between the two?
Correlation is one of the most misused statistics. The famous adage is that correlation does not imply causation, and the world is full of spurious or coincidental correlations. This is not entirely true in the case of fuel and truckload rates, but like most things, it’s complicated. The underlying market value is what determines a carrier’s ability to pass along their costs.
Fuel costs account for roughly 25% of the total operating cost of a truck, though this figure fluctuates as costs shift. According to the American Transportation Research Institute (ATRI), fuel costs fell from 28% to 21% of total operating costs between 2022 and 2024. The key takeaway is that fuel represents a significant portion of operating costs, even if its exact share varies.
When fuel prices rise sharply, so does their influence on trucking costs. The majority of truckload moves operate under long-term pricing agreements between shippers and service providers. A portion of fuel costs is separated out as a variable surcharge tied to the average price of diesel — typically the weekly DOE figure — so short-term fuel price changes do not affect contract rates, as those costs are passed along separately.
In the spot market, which the NTI measures, rates are typically quoted as all-inclusive totals with no component breakouts. Since all information about the load and its costs reflects current conditions, there is no need to separate costs into components. The price is simply what the market will bear at that point in time.
In 2022, the truckload market was at the beginning of a collapse. The market value for trucking services was near all-time highs, driven by a severe imbalance between supply and demand — freight demand far exceeded available capacity.
Demand (STVI in yellow) fell rapidly in March 2022 as many shippers realized that months of over-ordering had finally caught up with them. Pandemic-era quarantines were largely being lifted, and goods consumption declined. Meanwhile, truckload capacity had expanded dramatically over the prior two years.
