DOT Weight and Size Limit Regulations 2 — Questions and Answers
Question 1: What minimum semi-trailer length must states allow on the National Network under the Surface Transportation Assistance Act (STAA) of 1982?
- 45 feet
- 48 feet (Correct answer)
- 53 feet
- 60 feet
Correct answer: 48 feet
The STAA of 1982 required states to permit at least 48-foot semi-trailers on the National Network, establishing a federal floor for trailer lengths.
Question 2: Under Bridge Formula B, which variable most directly determines the maximum allowable weight for a group of axles?
- Gross vehicle weight rating
- Number of tires per axle
- Distance between the first and last axle of the group (Correct answer)
- Cargo hazard classification
Correct answer: Distance between the first and last axle of the group
Bridge Formula B uses the distance between the outermost axles of any consecutive group to calculate the maximum permissible weight on that group.
Question 3: Safety devices such as rear-view mirrors may extend beyond the 102-inch width limit by up to how much on each side?
- 3 inches per side
- 6 inches per side (Correct answer)
- 10 inches per side
- No extension is permitted
Correct answer: 6 inches per side
Federal regulations allow safety devices such as rear-view mirrors to extend up to 6 inches beyond the 102-inch width limit on each side of the vehicle.
Question 4: Which of the following vehicle types is typically exempt from federal length limitations under the STAA?
- Refrigerated trailers
- Bulk liquid tankers
- Automobile transporters (Correct answer)
- Flatbed trailers
Correct answer: Automobile transporters
Automobile and boat transporters are exempt from federal trailer length limitations under the STAA because of the unique nature of their cargo.
Question 5: At a permanent weigh station, the primary tool used to definitively verify axle weights for enforcement purposes is:
- A portable axle scale
- A weigh-in-motion sensor
- A certified static scale (Correct answer)
- A load cell dynamometer
Correct answer: A certified static scale
Certified static scales at fixed weigh stations are the standard for legally defensible axle and gross weight measurements during DOT enforcement actions.
Question 6: Under 23 CFR Part 658, which road network is required to accommodate vehicles meeting federal size and weight standards?
- All public roads in the United States
- The National Network of designated highways (Correct answer)
- All state-maintained highways
- Interstate highways only
Correct answer: The National Network of designated highways
23 CFR Part 658 designates the National Network of highways that states must open to vehicles meeting federal size and weight standards.
Question 7: A vehicle with a 40-foot axle spread carrying multiple axle groups must comply with Bridge Formula B to protect:
- Roadway pavement only
- Bridge structures from overload stress (Correct answer)
- DOT inspector safety protocols
- FMCSA registration requirements
Correct answer: Bridge structures from overload stress
Bridge Formula B exists specifically to prevent concentrated loads from overstressing bridge structures as vehicles cross them.
DOT Weight and Size Limit Regulations 2
What minimum semi-trailer length must states allow on the National Network under the Surface Transportation Assistance Act (STAA) of 1982?