Seeing Hazards and Space Management
The General Knowledge exam uses this domain to test whether you see problems early and keep room to solve them. Hazard perception is graded as a skill: look far ahead, scan constantly, and treat every developing situation as a hazard until it is resolved.
Seeing hazards
- Aim your eyes 12-15 seconds ahead in urban traffic; at 55 mph that is roughly a quarter mile.
- Scan, do not stare: mirrors every 5-8 seconds, plus instruments, plus the road edge.
- Read clues: brake lights two cars ahead, a ball rolling into the street, a driver's head turning, construction signs, a car drifting in its lane, a pedestrian at a crosswalk with a phone in hand.
- Communicate early with signals, brake lights, and lane position; do not assume anyone sees you.
Space management
- Following distance: one second for each 10 feet of vehicle length below 40 mph, plus one second above 40 mph. At 40 mph and above, add the extra second.
- Keep a cushion on both sides - avoid riding beside another vehicle where a lane change would hit you.
- Leave an escape route ahead: a gap to the left, right, or shoulder.
- Check overhead clearance before entering an underpass or drive-through; bridge strikes are preventable.
- If someone tailgates, increase your own following distance so you can slow gradually rather than brake abruptly.
Worked example
A 65-foot combination travels at 55 mph. Reasoning: 65 feet ÷ 10 = 6.5, rounded to 7 seconds, plus 1 second because speed exceeds 40 mph, gives 8 seconds of following distance. Eight seconds at 55 mph, or about 81 feet per second, is roughly 645 feet - more than two football fields. A driver following at four seconds would have about 320 feet, less than half the needed cushion.
Traps
- Using the car rule of three or four seconds for a loaded combination.
- Counting seconds too fast; use a fixed roadside object and count deliberately.
- Forgetting that mirrors leave large blind spots - a car can disappear beside a trailer and stay hidden.
- Assuming a green light means the intersection is clear.