While each state can pass laws to govern the roads in its jurisdiction, most traffic laws are similar across the United States. Traffic signs follow the same principle. Individual states have the freedom to customize traffic signs to a certain degree, but the Manual on Uniform Traffic Control Devices (MUTCD) establishes baseline standards that all traffic signs must meet, regardless of jurisdiction.
Who writes traffic laws?
Traffic laws are usually written by state legislatures since each state can make its driving laws. Most state highway codes are based on the Uniform Vehicle Code, though no state has adopted it in its entirety. Still, having a common basis ensures that traffic laws are similar from one state to another, which is important since each state recognizes other states’ licenses as valid.
Each state makes its code of traffic laws available to the public. For state-specific information, consult your state’s Department of Motor Vehicles (DMV) or find a summary of state traffic laws online.
Common driving rules
Drivers must use the right side of the road
The only exception is the U.S. Virgin Islands where traffic proceeds on the left-hand side.
Drunk driving is prohibited in all states
A blood alcohol level of .08 is the legal threshold for drunk driving in nearly every state.
Every state has seat belt laws
These laws also define whether seat belt violations are a primary offense (where you can be stopped for violating the law) or a secondary offense (where you can be issued a ticket if you are stopped for something else). Learn more about seat belt laws by state.
Nearly every state requires auto insurance
Even among the few states that don’t require car insurance, drivers generally still need to prove that they meet certain financial responsibility requirements if they cause damage to others. Learn about the car insurance requirements in your state.
Right of way is given, not taken
Even when you have the right of way legally, you need to proceed with caution, especially when entering or exiting a roadway.
Yield right of way to emergency vehicles
If possible, pull over and wait for the emergency vehicle to pass. Learn about emergency vehicle passing rules.
Drivers proceed in the order they arrive at traffic stops
If two drivers arrive simultaneously, the one furthest to the right has the right of way. This also applies at 4-way stops.
Stop for school buses dropping off children
You must not only stop for school buses if you are following behind one but also when they’re on the other side of the road (unless there’s a physical barrier like a median dividing the road).
All states allow right turns at a red light
Unless an intersection has signage indicating otherwise, you can turn right on red. Drivers must first stop at the light and check for cross traffic before turning from the rightmost lane of their current street into the rightmost lane of the destination street.
Common traffic laws
These laws are more subject to state variation or involve less common driving scenarios but are still good to know.
Traffic proceeds counterclockwise in roundabouts
Though the United States has historically used four-way stops to regulate intersections that don’t have traffic lights, roundabouts are becoming more common. Learn how to drive in a roundabout.
Keep right on multi-lane highways
State laws aren’t well standardized about handling driving in the left lane, but most states have some rules about using the left lane to pass. Learn about driving in the left lane.
Maximum speed limits vary by state
All states establish different limits for different kinds of roads and speed limit laws.
Mobile phone use varies by state
According to Governors Highway Safety Association, most states have distracted driving laws that impose restrictions on cell phone use.
The minimum age for a learner’s permit varies by state
Some states issue learner’s permits to people as young as 14, but most states allow teens to get a learner’s permit between 15 and 16.5 years old.
Traffic sign rules
It’s important to know the meaning of traffic signs. According to the MUTCD, the color of the sign tells you a lot about what it’s conveying:
- Red is only used on stop, yield, and prohibition signs
- White background is for regulatory signs such as speed limit signs
- Yellow is for warning messages like an upcoming railroad crossing
- Green indicates allowed traffic movement or directional guidance like highway exit signs
- Orange is for construction like detours or workers ahead signs
- Fluorescent yellow and green are for pedestrian and school crossings
- Blue alerts drivers to upcoming services like rest areas
- Brown indicates cultural, recreation, or tourist attractions
The sign’s shape gives you information too. Squares or vertical rectangles indicate traffic regulations like a speed limit sign, diamonds are for warnings, horizontal rectangles offer guidance, and pentagons are for school zones. Having a clear understanding of the rules of the road can help make you a safe driver. Learn more about the rules of road and take our rules of the road driving quiz.