Cross-Border Study
The Inspection Paradox
What an inspection-based safety score measures, tested on the motor carriers inspected most
Published: October 2026 • 1.83 million property motor carriers • FMCSA inspections through September 2026, crashes through August 2026
Key Findings
FMCSA's Inspection Selection System (ISS) tells roadside inspectors which trucks to pull in. It ranks motor carriers mostly on what their past inspections recorded, along with crashes and out-of-service orders. FMCSA does not publish ISS values, so every ISS figure here comes from a rebuild from FMCSA's public data with its published method. Motor carriers domiciled in Mexico are inspected more than any other group on US roads — almost entirely at inspection sites in US border counties, under enforcement that changed in 2025. That makes them a useful test. If the score measures crash risk, it should move with their crashes. If it measures inspection, it should move with what inspectors record.
The paradox: in mid-2025 inspectors stepped up enforcement of the English-language proficiency requirement for truck drivers. At the southern border recorded violations of it went from almost none to about three for every ten Mexican driver inspections, and the share of Mexican motor carriers ISS flags “Inspect” rose from about 6% to 29% by September 2026. Their crash rate on US roads showed no detectable rise: 0.90× after against before (95% interval 0.73–1.13), far from the fivefold rise in flags. Without those violations, ISS would flag 6.4% of them, against 4.7% of Canadian motor carriers. The score followed the enforcement, not the crashes.
Three Inspection Regimes
Ninety-six percent of Mexican motor carriers hold US authority only for the border commercial zones (FMCSA authority records, May 2026). Almost every inspection of their trucks happens in a US border county, four in five at a fixed facility, often by a federal inspector, and most are full Level 1 inspections. Canadian motor carriers are inspected mainly at fixed sites such as weigh stations and ports of entry. US interstate motor carriers are inspected wherever they drive, one time in six after a traffic stop. US interstate motor carriers based in border counties share many of the Mexican motor carriers' inspection sites, so they are shown as a fourth group.
| 24 months to October 2026 | Mexican | Canadian | US interstate | US interstate, border counties |
|---|---|---|---|---|
| Motor carriers | 5,463 | 11,843 | 564,500 | 12,021 |
| Inspected at least once | 75% | 56% | 56% | 72% |
| Inspections per motor carrier | 59.9 | 11.6 | 6.8 | 20.3 |
| Inspections per 100 truck-years | 301 | 56 | 44 | 140 |
| Inspections in a US border county | 99% | 1% | 6% | 51% |
| At a fixed facility | 82% | 71% | 49% | 65% |
| By a federal inspector | 39% | 0.4% | 1.1% | 10% |
| Full (Level 1) inspections | 62% | 18% | 24% | 33% |
| After a traffic stop | 0.8% | 10% | 16% | 9% |
Truck-years count each motor carrier's power units (at least as many as were seen at roadside) for the months it existed in the window. For Mexican motor carriers the roadside count also picks up second units recorded only as “other” (probably trailers), so their per-truck-year figures here run about 10% low. US interstate = motor carriers registered with FMCSA for interstate or hazmat operation (its AB file); most US motor carriers are intrastate, are rarely inspected and are left out of the comparison.
What the inspections find
| Rate | Mexican | Canadian | US interstate | US interstate, border counties |
|---|---|---|---|---|
| Vehicle-maintenance violations per vehicle inspection | 2.86 | 0.88 | 1.16 | 1.40 |
| Vehicle inspections with a vehicle placed out of service | 23.8% | 15.8% | 22.4% | 20.4% |
| Unsafe-driving violations per 100 driver inspections | 0.5 | 9.1 | 12.8 | 5.4 |
| Hours-of-service violations per 100 driver inspections | 0.8 | 13.8 | 12.9 | 14.3 |
| English-proficiency violations per 100 driver inspections (24-month average; about 30 since July 2025) | 20.0 | 0.1 | 0.8 | 4.6 |
Same county, same kind of check. Part of the Mexican vehicle-maintenance excess is the kind of inspection. Compared with US interstate trucks inspected in the same border county, by the same type of inspector (federal or state), at the same level and type of location, Mexican trucks draw 1.40× the vehicle-maintenance violations (95% interval 1.27–1.52) and 1.20× the vehicle out-of-service orders. Most of what remains is the trucks' age: Mexican power units inspected at the border are a median 10 years old, against 6 for US interstate trucks (30% against 6% are 15 or older). Compared at the same model year as well, Mexican trucks draw 1.10× the vehicle-maintenance violations (1.01–1.17) and no more out-of-service orders (0.98×). Their drivers draw a tenth of the hours-of-service violations and a third of the unsafe-driving violations. That describes short border runs seen at fixed sites, not better driving: Mexico's few long-haul motor carriers draw 5.0 hours-of-service violations per 100 driver inspections, against 0.7 for zone motor carriers. Unsafe-driving violations come largely from traffic stops: one US interstate inspection in six follows a stop, against fewer than one Mexican inspection in a hundred. (The interval allows for variation between motor carriers, not between inspection sites.)
How ISS Sorts the Motor Carriers
ISS ranks each motor carrier against peers with similar inspection counts in each of FMCSA's seven safety categories (BASICs), crashes included. Motor carriers under an out-of-service order go straight to Inspect, and motor carriers with alerts in the riskier combinations go to Inspect (scores 75–100). Motor carriers without enough inspections to be ranked are scored on fleet size and inspection history and land in Optional (50–74). Ranked motor carriers without alerts go to Pass (1–49). FMCSA does not publish ISS values, so they were rebuilt from FMCSA's public files with its published method (see Methodology).
Share of motor carriers flagged “Inspect”, September 2026
As scored, and with English-proficiency violations removed from every motor carrier's record
| Group | Inspect, as scored | Inspect, without English-proficiency violations | Enough data to be ranked |
|---|---|---|---|
| Mexican | 29.4% | 6.4% | 67% |
| US interstate, border counties | 11.1% | 10.4% | 56% |
| Canadian | 4.7% | 4.7% | 38% |
| US interstate | 3.8% | 3.7% | 33% |
| All US motor carriers | 1.3% | 1.3% | 14% |
Motor carriers graded by Fleetidy and present in FMCSA's September 2026 SMS release. Shares leave out the monthly random draw that sends 1% of unranked motor carriers to Inspect; it would add 0.4–0.9 points.
What sends Mexican motor carriers to Inspect. 97% of the Mexican motor carriers ISS flags carry a Driver Fitness alert, almost always alongside a Vehicle Maintenance alert. Nine in ten Mexican Driver Fitness violations are for English proficiency. Take those violations out and the Mexican Inspect share falls to 6.4%, against 4.7% for Canadian motor carriers and 10.4% for US interstate motor carriers based in the same border counties. A Vehicle Maintenance alert on its own sends a motor carrier only to Optional.
What inspection volume does, and doesn't, do. Most of FMCSA's measures (all but unsafe driving and crashes) are averages per relevant inspection, so being inspected more often does not raise them. Volume makes a motor carrier rankable. 56% of Mexican motor carriers have enough inspection data for a Vehicle Maintenance percentile, against 9% of US interstate motor carriers, and a motor carrier with no percentile reaches Inspect only through an out-of-service order or the random monthly draw.
One Violation, Five Times the Flags
English-language proficiency has long been a federal requirement for commercial drivers (49 CFR 391.11(b)(2)). Roadside enforcement of it was stepped up in mid-2025, and since 25 June 2025 a driver who fails the check can be placed out of service. At the southern border, violations went from almost none in early 2025 to about 0.3 per Mexican driver inspection from July 2025 on. Most were written under the border-zone code, without an out-of-service order. Each one still counts toward the Driver Fitness category ISS ranks. That allows a before-and-after comparison: if the flags tracked crash risk, Mexican motor carriers' recorded crashes should have risen with them, relative to groups the change barely touched. The data cannot rule out other changes in fleets, routes or exposure over the same months, which is why the comparison groups matter.
English-proficiency violations
Per Mexican driver inspection, by quarter
Flagged “Inspect” by ISS
Mexican motor carriers, by data date
Crashes on US roads
Mexican motor carriers, per 100 truck-years
The vertical line marks 25 June 2025; the shaded band is the 95% interval of each quarter's crash rate. ISS was not rebuilt between August 2025 and February 2026, so that stretch of the line is left open. ISS values before 2026 are rebuilt from FMCSA's inspection records with 12–21 months of history instead of 24, which can understate the earliest shares by up to a sixth; it does not explain the rise. The partial third quarter of 2026 is left out of the crash series.
| Group | Jan 2024 – Mar 2025 | Jul 2025 – Jun 2026 | After ÷ before (95% interval) |
|---|---|---|---|
| Mexican | 0.297 | 0.269 | 0.90 (0.73–1.13) |
| Mexican, border commercial zone | 0.247 | 0.244 | 0.99 (0.78–1.26) |
| Canadian | 1.683 | 1.667 | 0.99 (0.93–1.05) |
| US interstate | 2.023 | 2.031 | 1.00 (0.99–1.01) |
| US interstate, border counties | 2.354 | 2.320 | 0.99 (0.93–1.05) |
April–June 2025, the quarter the change began, is left out. Mexican motor carriers had 196 recorded crashes before and 147 after. Adjusting recent months for late reporting changes none of the ratios by more than 0.02. Set against US interstate motor carriers in the same border counties, the Mexican change is 0.92× (0.73–1.17). Both periods use each motor carrier's October 2026 fleet and count motor carriers still graded then; those motor carriers hold 95–98% of Mexican motor carriers' recorded crashes in every quarter, so motor carriers that left do not bend the series.
Does the Flag Find the Riskier Motor Carriers?
Inside one group, ISS's flag does point at fleets with more crashes per truck. But it points mostly at the busiest fleets: the ones on the road, and in front of inspectors, the most. In the US, busy fleets have more crashes per truck mostly because their trucks cover more miles. Measure per mile driven, or against what a fleet's size, operation and activity would predict, and in the US most of the gap goes away.
US interstate motor carriers: crash rate of motor carriers flagged “Inspect” ÷ everyone else
Same flags, same crashes (September 2024 – August 2026), three ways of measuring exposure. 1.0 = no difference.
| Inspect ÷ everyone else | Per truck-year | Per mile driven | Against expected |
|---|---|---|---|
| US interstate | 1.91 (1.82–2.00) | 1.05 (1.01–1.08) | 1.02 (0.99–1.05) |
| US interstate, border counties | 1.60 (1.48–1.76) | 1.08 (0.96–1.20) | 1.17 (1.08–1.28) |
| Canadian | 1.74 (1.52–1.98) | 1.32 (1.16–1.50) | 1.34 (1.22–1.47) |
| Mexican | 1.84 (1.13–3.39) | 1.55 (1.00–2.55) | 1.34 (0.94–2.09) |
Flags rebuilt from FMCSA's September 2026 release, built from the five public safety categories so the crash category does not count the same crashes twice. “Expected” is the crash rate Fleetidy's model assigns a fleet of that size, operation, tenure and inspection activity. Per mile uses the mileage motor carriers report to FMCSA, where it is plausible. Each column compares Inspect motor carriers with the rest on that basis. Intervals from resampling motor carriers.
Looking forward gives the same answer. Among US interstate motor carriers that the rebuilt ISS flags from FMCSA's late-February 2026 release, crashes in the following five months ran 1.94× the rest per truck-year, and 1.03× (0.99–1.06) the rest once each fleet's expected crashes are taken into account. Being flagged brings more inspections, which the expected rate counts as activity; counting activity from before the release instead leaves the forward ratio at 1.03. Per mile, a basis the flag cannot touch, the US gap is still only 5%. Canada keeps a modest excess on the same-period data, but in the forward test its 1.13× cannot be told apart from none. Mexican motor carriers have too few crashes to separate the flag from exposure. The same goes for Mexican motor carriers flagged only because of English-proficiency violations: they are the fleets that cross the border most, and these data cannot separate how often a fleet crosses from how likely it is to crash.
The 1–100 value is not ordered by crashes per truck. Motor carriers ISS scores 50–74 for lack of data have fewer crashes per truck than the ranked motor carriers it scores 1–49.
What US Crash Records Can — and Cannot — Say
FMCSA's crash file records crashes on US roads. For a Mexican motor carrier that is usually a short shuttle across the border; the rest of its driving happens where the record cannot see it. So the exposure base decides the answer to “who crashes less?”.
| Recordable crashes, 24 months | Mexican | Canadian | US interstate | US interstate, border counties |
|---|---|---|---|---|
| Per 100 truck-years | 0.26 | 1.60 | 2.02 | 2.33 |
| Per million miles reported | 0.25 | 0.22 | 0.56 | 0.40 |
| Motor carriers with plausible reported mileage | 52% | 66% | 67% | 67% |
| Share of crashes with an injury but no death | 48% | 28% | 34% | 37% |
- Per truck, the US record holds far fewer Mexican crashes: a sixth to a quarter of the Canadian rate (0.16× as counted here, 0.18× on typed power units only, where the Mexican rate is 0.29 per 100 truck-years, and 0.23× on the power units motor carriers file).
- Per mile reported, Mexican motor carriers' US crash rate is about Canada's or higher: 1.14× to 1.36× depending on how reported mileage is screened, and below it on none of the screens. Those miles may include driving in Mexico.
- Inside Mexico's own fleets, motor carriers limited to the border zones and motor carriers with long-haul authority differ more than four-fold per truck (0.22 vs. 0.97 per 100 truck-years). Per mile reported they cannot be told apart (0.24 vs. 0.25 per million, with a wide interval: the long-haul group is 79 motor carriers, one of which holds nearly half its crashes).
- 87% of the recorded crashes of border-zone motor carriers happen in US counties on the Mexican border. Those with plausible mileage filings report a median 3,853 miles per truck a year.
- Injury crashes make up a larger share of Mexican crashes, which fits minor crashes going unrecorded, or simply a different kind of driving. The data cannot tell which.
What follows: neither exposure base supports calling one country's motor carriers safer than another's. The defensible tests compare motor carriers within one group, or one group with itself over time. That is how this study uses the cross-border contrast.
A Score Built to Forecast Crashes
Fleetidy's FRED Score starts from a different question: how many recordable crashes will this motor carrier have per truck-year? It forecasts from the motor carrier's class: size, operation, tenure, country of domicile, how recently it filed and the mileage it reported, how much of its filed fleet the roadside record sees, and how often and how it is inspected. It then adjusts for its drivers' unsafe-driving and hours-of-service violations, for its violation and out-of-service rates measured against what inspections of the same level, in the same state usually find, and for the motor carrier's own crash record. The method is described in the methodology and tested in the validation study. Here it is set beside ISS on the same motor carriers.
| Group | FRED forecast | ISS |
|---|---|---|
| US interstate | 0.57 (0.56–0.58) | 0.22 (0.20–0.24) |
| Canadian | 0.47 (0.42–0.53) | 0.26 (0.21–0.33) |
| Mexican | 0.27 (0.09–0.42) | 0.16 (0.00–0.33) |
Internal validation: motor carriers left out of the model's fit (its design and credibility constants were chosen on them), scored at the same ten monthly origins (November 2024 to August 2025) and 12-month outcomes the model was fitted on — not a later period. ISS is ranked with unranked motor carriers placed below Pass, which ranks better than its own 1–100 value. Intervals resample motor carriers; origins are weighted by how complete the rebuilt ISS history is at each. The Mexican difference is not statistically clear: there are too few crashes.
- At equal exposure. Take the riskiest-looking 10% of US interstate truck-years by each measure. The forecast's picks had 1.51× (1.39–1.65) the crash rate of ISS's picks; for Canadian motor carriers, 1.39× (1.11–1.72).
- Most of the lead is exposure. A fleet's class alone (size, operation, tenure, activity and domicile, with no violation or crash history) ranks US interstate crashes at 0.54. Most of the forecast's lead over ISS comes from that exposure information, not from violation or crash history.
- Enforcement changes barely move it. Removing every English-proficiency violation changes Mexican motor carriers' violation adjustment by less than a quarter of one percent on average, and moves 30 of 5,463 Mexican grades (24 up, 6 down).
- The level is right in each group: realized crashes ÷ forecast 0.98 (0.70–1.29) for Mexican, 1.02 for Canadian and 1.01 for US interstate motor carriers. The model allows for domicile, so this is expected by construction; the ranking above is the real test.
- Where it is weakest. US interstate motor carriers based in border counties realized 0.80 (0.74–0.88) of their forecast, a misfit of its inspection-activity terms that shows in the fitting data too. Inside Mexico it ranks weakly (0.27), and much of its violation adjustment for Mexican motor carriers rests on their drivers' low unsafe-driving and hours-of-service rates, which too few crashes can test.
Methodology & Caveats
ISS is rebuilt, not official. FMCSA does not publish ISS values (the ISS field in its public QCMobile API was empty for all 24 motor carriers we checked on 29 October 2026), or safety percentiles for property motor carriers. Both were rebuilt from FMCSA's public SMS files with its published method: the SMS Methodology (v3.21, 2026) and the ISS-CSA algorithm description (2012). The published measures recompute exactly for four of the five public categories (unsafe driving depends on fleet history FMCSA does not publish). FMCSA still publishes percentiles for passenger motor carriers, which are ranked against property motor carriers in the same groups; the rebuild reproduces them exactly for hours of service, driver fitness and drugs/alcohol, for 99.7% of motor carriers in vehicle maintenance, and within one point for 99% in unsafe driving. The final Inspect / Optional / Pass step follows FMCSA's documents and cannot be checked against an official value. Alert thresholds for property motor carriers come from the methodology document.
US crashes only. Outcomes are federally recordable crashes in FMCSA's crash file, which covers US roads. Every cross-border comparison carries that limit, which is why the conclusions rest on comparisons within a group and over time.
Exposure. Truck-years use each motor carrier's filed power units, raised to the number seen at roadside where that is larger, for the months it existed. Per-mile rates use only reported mileage of 1,000–300,000 miles per truck a year: 52% of Mexican motor carriers qualify, against two-thirds of Canadian and US interstate motor carriers. Windows in the past use each motor carrier's October 2026 fleet and count only motor carriers still graded then (for Mexican motor carriers, 95–98% of recorded crashes in every quarter). For Mexican motor carriers the roadside count also picks up about 5,400 second units recorded only as “other”; on typed power units their crash rates are about a tenth higher, and comparisons within a group are unaffected.
Windows. Inspections and violations: the 24 months behind each FMCSA release (September 2026 and late February 2026). Same-period crashes: September 2024 to August 2026, scored with the five public categories. Forward crashes: March to July 2026 after the late-February release. Before and after: January 2024 to March 2025 against July 2025 to June 2026.
Earlier ISS dates. ISS for dates before 2026 is rebuilt from FMCSA's inspection and violation records FMCSA had received by each date, in their current version, with today's motor carrier census. The public files start in October 2023, so the earliest dates see 12 rather than 24 months of history.
Small numbers. Mexican motor carriers have few recorded crashes (280 in 24 months), so every Mexican figure carries a wide interval, shown where it matters. The FRED comparison uses motor carriers left out of the model's fit, though its design and credibility constants were chosen on them, inside the period the model was fitted on, not a later period.
What this is not. This is a study of what a score measures. It takes no position on English-language proficiency rules or on enforcement priorities, and ISS was built to pick trucks for inspection, not to price risk. The trouble starts when an inspection-based measure is read as a safety ranking across motor carriers inspected in very different ways.