Traffic Law Glossary
Comprehensive definitions of U.S. traffic law terms, road markings, signs, and driving regulations. All definitions based on MUTCD standards and state traffic statutes.
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Advisory Speed
A recommended safe speed shown on yellow signs (often with curves or ramps), typically lower than the posted speed limit. Unlike regulatory speed limits, advisory speeds are suggestions based on road geometry and conditions.
All-Way Stop
An intersection where all approaches have stop signs. The first vehicle to arrive has right-of-way; when vehicles arrive simultaneously, the vehicle on the right has priority.
Examples:
- Four-way stop at residential intersections
- Three-way stop at T-intersections
Bicycle Lane (Bike Lane)
A portion of roadway designated by striping, signage, and pavement markings for preferential or exclusive use by bicyclists. Often marked with solid white lines and bicycle symbols.
Broken Yellow Line
A dashed yellow centerline marking indicating that passing is permitted when safe to do so. Drivers may cross the line to pass slower vehicles if they have clear visibility and adequate space.
Center Left Turn Lane (TWLTL)
A center lane bordered by solid yellow and broken yellow lines, reserved exclusively for vehicles making left turns from either direction. Also called a Two-Way Left Turn Lane. Drivers may not use it for through traffic or passing.
Controlled Access Highway
A roadway where access is limited to specific on-ramps and off-ramps. No driveways, crossroads at grade, or direct property access. Examples include interstates and most freeways.
Examples:
- Interstate highways (I-95, I-10)
- State freeways and turnpikes
Crosswalk
The portion of roadway designated for pedestrian crossing, either marked by painted lines or unmarked at an intersection. Pedestrians in crosswalks generally have right-of-way over turning vehicles.
Diamond Lane
Common name for High Occupancy Vehicle (HOV) lanes or carpool lanes, marked with white diamond symbols on the pavement. Restricted to vehicles meeting minimum occupancy requirements during specified hours.
Do Not Enter Sign
A rectangular red and white regulatory sign (R5-1) indicating that traffic is prohibited from entering a roadway or area. Commonly seen at exit ramps and one-way street exits.
Double Solid Yellow Line
Two parallel solid yellow lines marking the center of a two-way roadway, indicating a no-passing zone in both directions. Crossing is generally prohibited except for left turns into driveways or to avoid obstructions.
Double White Line
Two parallel solid white lines indicating lane separation where crossing is prohibited. Commonly used to separate through lanes from turn-only lanes or to protect bike lanes and HOV lanes.
Edge Line
A solid white or yellow line marking the edge of the roadway. White edge lines mark the right edge of the roadway; yellow edge lines mark the left edge on divided highways or one-way streets.
Expressway
A divided highway with partial or full access control, designed for higher-speed traffic. May have at-grade intersections with traffic signals, unlike freeways which have no at-grade crossings.
Examples:
- US Routes with limited access
- State highways with divided lanes
Flashing Yellow Arrow
A traffic signal indication permitting left turns after yielding to oncoming traffic and pedestrians. Indicates a permissive left turn phase where drivers must use judgment.
Freeway
A controlled-access highway with no at-grade intersections, traffic signals, or stop signs. All traffic enters and exits via ramps. Typically has a posted minimum speed as well as maximum speed limit.
Examples:
- All Interstate highways
- Limited-access state routes
Gore Point
The triangular area where a freeway entrance or exit ramp separates from or merges with the main roadway. Entering the gore area is typically prohibited and marked with diagonal white stripes.
Guide Sign
Informational signs providing direction, distance, route markers, and points of interest. Typically rectangular with green (highway), blue (services), or brown (recreation) backgrounds.
High Occupancy Vehicle (HOV) Lane
A restricted lane designated for vehicles carrying a minimum number of occupants (typically 2 or 3+). Also known as carpool lanes or diamond lanes. Access and hours of operation are controlled by signs and pavement markings.
Intersection
The area where two or more roadways meet or cross at grade. Includes the entire width of the roadways and may be controlled by signs, signals, or uncontrolled (requiring yield to right).
Examples:
- Four-way intersections with traffic signals
- T-intersections with stop signs
- Uncontrolled intersections (yield to right rule)
Lane Line
Pavement markings separating lanes of traffic moving in the same direction. White broken lines indicate lane changes are permitted; solid white lines discourage lane changes.
Left on Red
A maneuver permitting left turns at a red signal from a one-way street onto another one-way street (where allowed by state law). Must come to complete stop and yield to all traffic and pedestrians first.
Median
The area separating opposing lanes of traffic on a divided roadway. May be raised, depressed, or marked with pavement markings. Can include barriers, landscaping, or turn lanes.
MUTCD
Manual on Uniform Traffic Control Devices - the federal standard defining all traffic signs, signals, and pavement markings in the United States. Published by the Federal Highway Administration (FHWA).
Examples:
- Defines sign colors, shapes, and sizes
- Standardizes pavement marking patterns
- Sets signal timing and display requirements
No Passing Zone
A section of roadway where passing is prohibited, marked by solid yellow centerlines and often accompanied by pennant-shaped yellow warning signs (W14-3).
One-Way Street
A roadway where all traffic must travel in a single designated direction. Marked with ONE WAY signs and sometimes by arrows on the pavement.
Pavement Markings
All lines, symbols, words, and patterns applied to roadway surfaces to regulate, warn, or guide traffic. Includes centerlines, edge lines, lane lines, crosswalks, and symbols.
Pedestrian Right-of-Way
The legal priority pedestrians have over vehicles when in a crosswalk or lawfully crossing at an intersection. Drivers must yield to pedestrians in crosswalks, whether marked or unmarked.
Permissive Turn
A turn made on a circular green signal or flashing yellow arrow, where the driver must yield to oncoming traffic and pedestrians. Contrasts with protected turns (green arrow).
Protected Turn
A turn made on a green arrow signal, where the driver has exclusive right-of-way and oncoming traffic is stopped by a red signal.
Regulatory Sign
A sign that informs drivers of traffic laws or regulations. Typically rectangular with white background and black text, or special shapes like STOP (octagon) and YIELD (triangle). Non-compliance may result in citations.
Examples:
- STOP, YIELD, Speed Limit
- NO TURN ON RED, DO NOT ENTER
- ONE WAY, NO PARKING
Right Turn on Red
A permitted maneuver allowing right turns at a red signal after coming to a complete stop and yielding to all traffic and pedestrians, unless prohibited by a NO TURN ON RED sign or red arrow.
Right-of-Way
The legal right of a vehicle or pedestrian to proceed in priority over other traffic. Determined by traffic control devices, traffic laws, and established rules (e.g., vehicle on right at uncontrolled intersections).
Roundabout
A circular intersection where traffic flows counterclockwise around a central island. Entering traffic must yield to circulating traffic. Designed to reduce speeds and conflict points compared to traditional intersections.
School Zone
A designated area near schools with reduced speed limits during specified times (typically when children are arriving or departing). Marked with pentagonal yellow-green signs and often includes flashing beacons.
Shared Lane Marking (Sharrow)
A pavement marking showing a bicycle symbol with two chevrons above it, indicating a lane shared by bicyclists and motor vehicles. Alerts drivers to expect bicyclists and shows cyclists proper lane positioning.
Shoulder
The paved or unpaved area adjacent to the roadway edge, available for emergency use, disabled vehicles, or as specified by signs. Driving on shoulders is typically prohibited except in emergencies.
Solid White Line
A pavement marking discouraging lane changes. When used as a lane line, crossing is legal but discouraged. When doubled, crossing is typically prohibited.
Solid Yellow Line
A pavement marking on the left side of a lane indicating passing is prohibited from that side. On a two-lane road, one direction may have solid yellow (no passing) while the opposite has broken yellow (passing permitted).
Stop Bar
A solid white line extending across approach lanes at an intersection or crosswalk, indicating where vehicles must stop when required by a sign or signal.
Traffic Control Device
Any sign, signal, marking, or device placed on, above, or adjacent to a roadway to regulate, warn, or guide traffic. Includes traffic signals, signs, and pavement markings.
Turn Lane
A dedicated lane for turning traffic, often marked with arrows on the pavement and separated by solid white lines. May be exclusive (turn only) or optional (turn or through).
Two-Way Left Turn Lane (TWLTL)
See Center Left Turn Lane. A center lane marked by solid yellow and broken yellow lines, reserved exclusively for left turns from either direction of travel.
U-Turn
A 180-degree turn that reverses direction of travel. Legality varies by state and location. Often prohibited near curves, hills, at intersections with signals, and within business districts unless signed otherwise.
Warning Sign
A sign alerting drivers to conditions or hazards ahead. Typically diamond-shaped with yellow background and black symbols or text. Examples include curve ahead, merge, and pedestrian crossing signs.
Yellow Line
Pavement markings separating traffic flowing in opposite directions. May be solid (no passing), broken (passing permitted), or a combination.
Yield Sign
A downward-pointing triangular sign with red border and white background, requiring drivers to slow down and give right-of-way to other traffic. Unlike STOP signs, a full stop is only required if traffic conditions demand it.
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Legal Disclaimer
This glossary is for educational purposes only and should not be considered legal advice. Traffic laws and their interpretations vary by jurisdiction and change over time. Always consult your state's traffic code, local authorities, or legal professionals for specific situations and official guidance.