🇺🇸 United States

US driving basics

The United States is a federation of 50 states, each with its own traffic code. A few core rules, however, apply almost everywhere. Here's the minimum a visitor needs to know before driving — with an official source for every claim.

Which side of the road

The US drives on the right-hand side of the road. This is uniform throughout all 50 states and US territories and is embedded in the federal sign and lane conventions of the MUTCD.^[1]

Speed limits — always MPH

There is no national speed limit. The national 55 mph cap was repealed in 1995. Each state sets its own maximum; counties and cities may set lower limits on local roads. Where no sign is posted, statutory limits still apply.^[2]

Speed limits in the continental US are always shown in miles per hour (mph), never kilometers per hour, on white rectangular regulatory signs per MUTCD Chapter 2B.^[1]

For state-by-state top speed limits, see our state-by-state comparison.

Seat belts

Seat belt laws are set by each state, not the federal government. Every state except New Hampshire requires adult front-seat occupants to wear a seat belt. Thirty states plus DC also mandate rear-seat seat belts.^[3][4]

Thirty-four states plus DC have primary enforcement — an officer can stop a driver solely for a seat belt violation; fifteen have secondary enforcement.^[4]

Impaired driving (DUI / DWI)

Driving under the influence of alcohol is illegal in every US jurisdiction. The per-se illegal blood alcohol concentration (BAC) is 0.08 g/dL in all 50 states, DC, and Puerto Rico, with one exception: Utah lowered its limit to 0.05 g/dL effective December 30, 2018.^[5][6]

Drug-impaired driving is separately illegal nationwide; testing and thresholds vary by state.^[7]

Phones while driving

Cell phone rules are state-level. As of NHTSA's most recent compilation, 24 states plus DC, Puerto Rico, Guam, and the US Virgin Islands prohibit all drivers from using handheld cell phones. 48 states plus DC/PR/Guam/USVI ban text messaging for all drivers. No state completely bans all cell phone use.^[8][9]

For state-by-state phone law detail, see our comparison.

School buses

In all 50 states, DC, Guam, Puerto Rico, and the US Virgin Islands, it is illegal to pass a stopped school bus with its red lights flashing and its stop arm extended. Approaching vehicles in both directions must stop (with narrow exceptions for divided highways in some states).^[10]

Child car seats

Every state has child passenger safety laws, but specifics (age, weight, height cutoffs, booster requirements) vary. NHTSA recommends that all children under 13 ride in the back seat. If you're renting and traveling with children, confirm your rental company can provide the correct seat for your child's age and weight, or bring your own.^[11][12]

Move-over laws

Every US state and DC has a "move-over" law: when approaching a stopped emergency vehicle, tow truck, or highway maintenance vehicle on the shoulder with flashing lights, drivers must move over to a non-adjacent lane if safe, or slow down substantially.^[13]

What's NOT uniform

Everything else. Right-turn-on-red (almost always allowed, but with NYC as the famous exception), studded tires, helmet laws, marijuana-in-vehicle rules, minimum insurance amounts, and more all vary by state. See our state-by-state rules matrix for the 10 most-visited states.