Further Laboratory Testing of In-Vehicle Alcohol Test Devices
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Summary
This 1988 National Highway Traffic Safety Administration (NHTSA) technical report evaluates the accuracy and circumvention resistance of three commercially available in-vehicle alcohol test (IVAT) devices: Autosense, Guardian Interlock, and Safety Interlock. These ignition interlock systems are designed to prevent drivers with breath alcohol concentrations (BAC) above a preset threshold from starting their vehicles. The study was motivated by the need to assess whether these devices, which were increasingly being mandated for convicted drunk drivers, could be reliably fooled by motivated individuals using common household items or techniques. The researchers conducted laboratory tests on two units of each device, calibrated to a 0.03% BAC threshold. They assessed precision by introducing simulated breath samples ranging from 0.00% to 0.07% BAC. To evaluate circumvention strategies, they tested the devices against bogus breath samples (using balloons and plastic bags) and filtered air samples (using water filters and absorbent paper tubes). Specific anti-circumvention features were also analyzed, including the Safety Interlock’s temperature sensor, the Autosense’s high-pressure requirement, and the Guardian Interlock’s Coordinated Breath Pulse Access (CBPA), a timed puffing sequence intended to prevent sober bystanders from starting the car. Preliminary tests with ten sober volunteers assessed the difficulty of the CBPA requirement. The results indicated that, with one exception, the devices accurately prevented starts at BAC levels of 0.04% and above. However, none of the devices were immune to circumvention. The Safety Interlock’s temperature sensor made it harder to use room-temperature bogus samples, but heated samples could still fool the device. The Autosense’s high pressure requirement (13 inches of water) prevented the use of certain filtered air samples that could not generate sufficient pressure, but it was vulnerable to other methods. The Guardian Interlock’s CBPA feature proved effective at deterring naive, untrained bystanders, with only 33% of volunteers passing the easiest setting without practice. Nevertheless, motivated individuals with preplanning could defeat all three devices using various combinations of heating, filtering, or specific container types. The study concludes that while anti-circumvention features like temperature sensors, pressure requirements, and complex activation sequences increase the difficulty of fooling IVAT devices, they do not make them secure against a determined user. The findings highlight the limitations of laboratory-based security measures and suggest that real-world performance may vary. The authors caution against generalizing these results to all units or future models, noting that further field evaluation is necessary to understand how these devices perform under actual driving conditions.
Key finding
A motivated individual with preplanning and knowledge can circumvent in-vehicle alcohol test devices using bogus breath samples or filtered air, although features like temperature sensors and pressure requirements make such circumvention more difficult.
Methodology
lab_experiment
Sample size: 10
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 3 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 19 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Methodological Resource: validation psychometrics