Turn signal — under 45 mph100 feet before
Turn signal — 45 mph or more200 feet before
Following distance2-second rule
Following — bad weather4+ seconds
Passing clearanceAt least 2 feet to left
No passing (sight distance)Can't see 500 ft ahead
Headlight trigger (visibility)400 feet or less
High beams illuminatePerson at 200 ft
Low beams illuminatePerson at 75 ft
Taillights visible500 feet
Horn audible from200 feet
Brake lights visible (daylight)100 feet
RR crossing stop range15–50 feet from rail
Don't follow emergency vehicleWithin 100 feet (lights on)
💡 Headlights required from sunset to sunrise, when visibility is 400 ft or less, AND any time your wipers are on due to weather. Hydroplaning can start at just 30 mph in 1/8 inch of water.