CDL Combination Vehicles TestDriving Combination Vehicles SafelyHard
You are driving a combination vehicle and are approaching a bridge with a 'Low Clearance: 13 ft 6 in' sign. Your vehicle's total height is 13 feet 4 inches. What is the safest course of action?
- ASpeed up slightly to ensure momentum carries you through quickly.
- BProceed cautiously, as you have 2 inches of clearance.
- CStop and find an alternative route, as posted clearances may not account for road variations or measurement errors.
- DDrive in the center of the road to maximize overhead clearance.
Show answer & explanationAnswer & explanation
Correct answer: C. Stop and find an alternative route, as posted clearances may not account for road variations or measurement errors.
Always err on the side of caution with low clearances. Posted clearances may not account for repaved roads, variations in measurement, or factors like air suspension height changes. With only 2 inches of clearance, there is an unacceptably high risk of striking the bridge, which can have catastrophic consequences.
Why the other options are wrong
- A. Speeding up is extremely dangerous; it increases impact force if a collision occurs and can cause the vehicle to bounce, reducing effective clearance.
- B. 2 inches is a dangerously small margin, not accounting for any road irregularities, vehicle bounce, or measurement inaccuracies.
- D. Driving in the center of the road does not increase overhead clearance and may create other traffic hazards if you impede flow or cross into opposing lanes.
Low Clearance Safety
When approaching low clearances with a combination vehicle, always err on the side of caution. Even small margins can be dangerous due to variations or errors.
- Posted clearances are not always exact.
- Road variations, vehicle bounce can reduce clearance.
- Always find an alternative route if clearance is tight.
Memory trick: Clearance Close? Consider the Cross-Out.