49 CFR §393.82
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).