The Insurance Penalty: Why Small Fleets Pay Nearly Double Per Mile

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A complete walkthrough of why small fleets pay nearly double per mile for liability insurance — the ATRI data behind the size penalty, why nuclear verdicts drive up premiums even for fleets with no claims, and the four levers a small fleet actually controls at renewal.

• American Transportation Research Institute (ATRI) data show small carriers (25 trucks or fewer) paid 20.3 cents per mile for liability insurance in 2024 — nearly double the 10.4 cents per mile paid by carriers running 101 to 250 trucks — consuming close to 5 percent of small-fleet revenue.
• Heavy-duty truck-involved crash rates fell 2.6 percent from 2021 to 2024 while liability insurance premiums rose 18.6 percent to 10.2 cents per mile over the same span, outpacing consumer inflation by 5.4 percentage points, per ATRI.
• The driver is claims severity, not frequency: per-mile liability losses rose 33.1 percent from 2021 to 2024 (ATRI), and the U.S. Chamber of Commerce’s Institute for Legal Reform counted 135 “nuclear verdicts” over $10 million in 2024 totaling $31.3 billion, with the median verdict growing from $21 million in 2020 to $51 million in 2024.
• Commercial auto liability has been unprofitable for insurers every year since 2014 — a combined loss ratio of 107.2 in 2024, per ATRI’s analysis of insurer financial data — and industry-wide insurance costs climbed to roughly 10.6 cents per mile in 2025, the fifth straight year of above-inflation increases.
• The levers a small fleet actually controls: clean CSA Safety Measurement System scores, twelve months of documented dash camera and GPS tracking data at renewal, and a retention strategy (higher deductibles, self-insurance, or captives) discussed with a broker who understands motor carrier risk.

A ten-truck fleet and a two-hundred-truck fleet can run the same freight, the same routes, and the same safety record — and still pay wildly different rates for the exact same liability coverage. In 2024, carriers running 25 trucks or fewer paid 20.3 cents per mile for liability insurance, nearly double the 10.4 cents per mile paid by carriers running 101 to 250 trucks.

This is not a story about small fleets driving worse. Heavy-duty crash rates fell industry-wide over the same period premiums climbed — so size alone has become one of the biggest line items on a small fleet’s insurance bill, and almost nobody budgets for it as its own cost driver.

This post covers what’s actually driving the gap, why it isn’t about to close on its own, and the levers a small fleet genuinely controls before its next renewal quote comes back.

ATRI tracks per-mile liability insurance costs by fleet size every year, and the gap has become one of the starkest in trucking economics. Small carriers — 25 trucks or fewer — paid 20.3 cents per mile in 2024. Mid-size carriers running 101 to 250 trucks paid 10.4 cents per mile for the same coverage category.

For the small carrier, insurance now consumes close to 5 percent of total asset-based revenue — a share large enough to move a thin-margin year into a loss year on its own.

Heavy-duty truck-involved crash rates fell 2.6 percent industry-wide between 2021 and 2024, the same period liability insurance premium costs rose 18.6 percent to 10.2 cents per mile industry-wide, outpacing consumer inflation by 5.4 percentage points. Fewer crashes, higher premiums — the gap between those two lines is what a fleet owner is actually paying for.

ATRI’s research points to claims severity, not claims frequency, as the driver. Per-mile liability losses — what insurers actually pay out per crash claim — rose an average of 33.1 percent from 2021 to 2024 among the carriers ATRI surveyed. Fewer crashes are happening, but each one that reaches a courtroom now costs far more to resolve.

The clearest evidence of that shift sits outside trucking-specific data entirely. The U.S. Chamber of Commerce’s Institute for Legal Reform counted 135 “nuclear verdicts” — jury awards exceeding $10 million — against corporate defendants in 2024, totaling $31.3 billion. The median nuclear verdict has more than doubled since 2020, from $21 million to $51 million in 2024.

Insurers price every policy — including the ones written for fleets that have never had a claim — against the expectation that the next verdict could be one of those. Combined loss ratios for commercial auto liability have stayed above 100 every year since 2014, reaching 107.2 in 2024, meaning the industry has paid out more in claims than it collected in premiums for a decade straight.

By ATRI’s 2026 “Analysis of the Operational Costs of Trucking” report, covering full-year 2025 data, industry-wide insurance costs had climbed to roughly 10.6 cents per mile — a 3.9 percent increase over 2024 and the fifth straight year of increases faster than general inflation.

Nothing in the underlying claims-severity trend suggests that curve is about to bend down, which means the fleet-size gap identified in the 2024 data is a baseline to plan around at the next renewal, not a one-year anomaly to wait out.

A carrier’s Safety Measurement System data — the CSA BASICs scores FMCSA publishes — is one of the first things a commercial auto underwriter pulls. A clean Unsafe Driving and Crash Indicator history is one of the few levers a small fleet fully controls before a renewal quote comes back.

Documented use of dash cameras and GPS-based vehicle tracking is another lever underwriters price into a quote, because it gives a carrier real evidence — not just a claim — that a driver was not at fault, or that speed and hard-braking events are actively monitored and corrected. A fleet that can hand an underwriter twelve months of monitored driving data at renewal is negotiating from a different position than one that can only hand over a loss run.

ATRI’s research on carrier responses to rising premiums has found that fleets are increasingly retaining a larger share of primary risk — higher deductibles, self-insured retentions, or captive arrangements — specifically to reduce their total cost of risk over time. That is not a fit for every small carrier’s cash position, but it is a conversation worth having with a broker who understands motor carrier risk specifically.

The most common mistake is treating a premium increase as a market condition to wait out. The data says otherwise — this is the fifth consecutive year of above-inflation increases, and the fleet-size gap is structural, not cyclical.

The second mistake is shopping price alone at renewal without changing the underwriting file itself. The same CSA scores, the same absence of monitoring data, and the same loss run, presented to a different carrier, tend to produce the same number.

As the Responsible Fleet team has observed working with small fleets on cost control: the fleets that make progress on insurance costs are the ones that start building their underwriting file the day after a renewal closes, not the week before the next one opens.

None of this is a reason to shop for the cheapest quote and hope. It is a reason to change what gets shown to an underwriter — a clean CSA file, a year of documented safety monitoring data, and a considered view on how much risk the fleet retains itself.

As the Responsible Fleet team tells small fleet owners: the insurance number at renewal is mostly decided by what was built in the eleven months before it, not the two weeks of shopping around right before it.

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