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Difficulty: HardBlood Alcohol Concentration (BAC) Limits and Thresholds

Under statutory traffic safety laws, per se Blood Alcohol Concentration (BAC) limits establish strict thresholds based on driver age and vehicle operational class. Consider two separate drivers evaluated during routine traffic enforcement:

• Driver 1: A 29-year-old operating a private sedan with a measured BAC of 0.07%0.07\%.
• Driver 2: A 40-year-old operating a commercial tractor-trailer with a measured BAC of 0.05%0.05\%.

Based on standard legal BAC limits, which statement correctly evaluates whether either driver is operating at or above their statutory per se limit?

  1. A
    Neither driver has reached or exceeded their statutory per se BAC limit.
  2. B
    Driver 1 is operating at or above the per se limit, while Driver 2 is legally below the commercial threshold.
  3. Driver 2 is operating at or above the statutory per se limit, while Driver 1 is below the standard adult limit.Answer
  4. D
    Both drivers are operating at or above their respective statutory per se BAC limits.

Answer

Driver 2 is operating at or above the statutory per se limit, while Driver 1 is below the standard adult limit.
Under standard traffic laws, the per se illegal BAC limit for adult non-commercial drivers aged 21 or older is 0.08%0.08\%, whereas the strict per se limit for drivers operating a commercial motor vehicle is 0.04%0.04\%. Because Driver 1 registered 0.07%0.07\%, they are below the 0.08%0.08\% adult limit. Because Driver 2 registered 0.05%0.05\%, they are above the 0.04%0.04\% commercial limit.

Step-by-Step Solution

1
Identify the statutory per se BAC limit for Driver 1 (adult non-commercial).
For non-commercial drivers aged 21 and older, the legal per se limit is 0.08%0.08\%.
Driver 1 is 29 years old operating a private sedan, so a BAC of 0.07%0.07\% is below the 0.08%0.08\% threshold.
2
Identify the statutory per se BAC limit for Driver 2 (commercial vehicle operator).
For drivers operating a commercial motor vehicle, the legal per se limit is 0.04%0.04\%.
Driver 2 is operating a commercial tractor-trailer, so a BAC of 0.05%0.05\% exceeds the 0.04%0.04\% commercial threshold.
3
Compare both measured BAC results to their corresponding legal thresholds to determine compliance status.
Driver 1 (0.07%<0.08%0.07\% < 0.08\%) has not exceeded the legal limit, whereas Driver 2 (0.05%≥0.04%0.05\% \ge 0.04\%) has exceeded the commercial limit.
Evaluating both conditions together correctly identifies Driver 2 as over the per se threshold while Driver 1 remains below.

Key Concept

Statutory BAC legal limits vary by license type and vehicle class: 0.08%0.08\% for adult non-commercial drivers and 0.04%0.04\% for commercial motor vehicle operators.
Estimated Time:1m 30s
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Topics

Blood Alcohol Concentration (BAC) Limits and Thresholds

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