Safe driving and emergencies
Which method does the California Driver's Handbook recommend for keeping a safe following distance behind the vehicle ahead?
- The three-second rule. Correct answer
- One car length for every 10 mph of speed.
- Staying close enough to see the other driver's side mirrors.
Why
The handbook's tool against tailgating is the three-second rule: stay three seconds behind the vehicle ahead. The glossary explains how to measure it: pick a fixed point such as a sign, start counting when the vehicle ahead passes it, and if you reach that point before you finish counting to three, you are following too closely. The handbook uses the same figure elsewhere, when merging onto a highway and when following a motorcyclist. That space is what gives you time to react if the driver ahead brakes suddenly or makes a mistake. The one-car-length-per-10-mph guideline is an older rule of thumb that the handbook does not use. Seeing the other driver's mirrors is a rule about large trucks, and it works the other way around: when a truck's side mirrors are out of your view, you are out of the driver's. Add space when a tailgater is behind you and when following a motorcyclist over metal surfaces or gravel.
Where this comes from
California Driver's Handbook, June 2025 edition. The correct answer is The three-second rule.
- Section 8. Safe Driving › Be Aware of Your Surroundings › Tailgating (Following Too Closely), page 57
- Section 6. Navigating the Roads › Merging And Exiting › Merging, page 23
- Section 7. Laws and Rules of the Road › Sharing the Road › Motorcycles, page 44
- Section 7. Laws and Rules of the Road › Sharing the Road › Blind Spots (the No Zone), page 42
- Section 14. Glossary › three-second rule, page 84
The rule behind this one
Safe driving and emergencies in California goes through the whole topic, with the page of the California Driver's Handbook behind every rule.