In This Guide
The 6-Second Following Distance Rule
The CDL formula: 1 second per 10 feet of vehicle length plus 1 additional second for speeds over 40 mph. For a 50-foot truck at 50 mph: 50/10 = 5 + 1 = 6 seconds minimum.
| Vehicle Length | Speed | Minimum Following Distance |
|---|---|---|
| 40 ft (straight truck) | Under 40 mph | 4 seconds |
| 50 ft (tractor-trailer) | 55 mph | 6 seconds |
| 70 ft (large combo) | 65 mph | 8 seconds |
In Heavy Traffic
Increase following distance when traffic is heavy, when being tailgated, or when road conditions are poor. If someone cuts in front of you, drop back to re-establish your safe following distance.
In Bad Weather
Double your following distance in rain, snow, or fog. On icy roads, triple it. Stopping distance increases dramatically — a truck traveling 65 mph on a wet road needs nearly 600 feet to stop completely.
Source: FMCSA Safety Guidelines