Traffic Laws Study Guide

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Speed Limits

Speed limits are legally enforceable maximum speeds for specific road types and conditions. Understanding and following speed limits is crucial for safety and avoiding traffic violations.

Standard Speed Limits

Residential Areas

Typically 25 mph unless otherwise posted. School zones may reduce this to 15-20 mph during school hours.

Business Districts

Usually 25-30 mph. Heavy pedestrian traffic requires extra caution regardless of posted limits.

Rural Highways

Generally 55-65 mph. State highways outside city limits typically allow higher speeds.

Interstate Highways

Usually 65-75 mph depending on state. Some western states allow up to 80 mph on certain stretches.

Key Principles

Posted limits are maximums — You must drive slower when conditions warrant (rain, fog, ice, heavy traffic).
Basic speed law — Never drive faster than is safe for current conditions, even if below the posted limit.
Minimum speeds — Some highways post minimum speeds (usually 40-45 mph). Driving too slowly can also be dangerous.
School zones — Reduced speed limits (15-25 mph) during specified hours, usually when children are present.
Work zones — Fines are often doubled in active construction zones. Workers' safety is paramount.

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Right-of-Way Rules

Right-of-way rules determine which vehicle proceeds first in various traffic situations. Understanding these rules prevents accidents and keeps traffic flowing smoothly.

Intersections

Stop signs — First vehicle to arrive proceeds first. If multiple vehicles arrive simultaneously, the vehicle on the right has right-of-way.
Uncontrolled intersections — Vehicle on the right has right-of-way. Slow down and be prepared to yield.
T-intersections — Vehicles on the through road have right-of-way over vehicles on the terminating road.
Left turns — Must yield to oncoming traffic and pedestrians. Only proceed when safe and clear.
Traffic circles/roundabouts — Vehicles already in the circle have right-of-way. Enter only when there's a safe gap.

Special Situations

Emergency Vehicles

Always yield to emergency vehicles with sirens/lights. Pull to the right and stop if necessary.

Pedestrians

Always yield to pedestrians in crosswalks (marked or unmarked). They have absolute right-of-way.

School Buses

Stop when red lights flash, regardless of direction. Never pass a stopped school bus with flashing lights.

Funeral Processions

Yield to funeral processions. Don't cut through or pass a procession.

Important: Even if you have the right-of-way, you must do everything possible to avoid a collision. Right-of-way is yielded, not taken.

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DUI/DWI Laws

Driving under the influence (DUI) or driving while intoxicated (DWI) is one of the most serious traffic offenses, carrying severe legal and safety consequences.

Blood Alcohol Concentration (BAC) Limits

0.08% — Adult Drivers

Legal limit for drivers 21 and over in all 50 states. Commercial drivers have stricter limits.

0.04% — Commercial Drivers

Lower limit for CDL holders operating commercial vehicles.

0.00-0.02% — Under 21

Zero tolerance laws for minors. Any detectable alcohol is illegal.

Enhanced Penalties

BAC of 0.15% or higher often results in increased fines and longer license suspensions.

Consequences

First offense — License suspension (3-12 months), fines ($500-$2,000), possible jail time (up to 6 months), mandatory DUI classes.
Second offense — Longer suspension (1-2 years), higher fines ($1,000-$5,000), jail time (10 days to 1 year), ignition interlock device required.
Third offense — Felony in many states, extended jail time (1-5 years), license revocation, vehicle impoundment.
Refusal to test — Implied consent laws mean automatic license suspension (often longer than DUI suspension).

Other Impairing Substances

DUI laws apply to all impairing substances, including:

Illegal drugs (marijuana, cocaine, methamphetamine, etc.)
Prescription medications (opioids, benzodiazepines, sleep aids)
Over-the-counter drugs (antihistamines, cough medicine with DXM)
Combinations of alcohol and drugs (even small amounts)

Zero Tolerance: If you're under 21, any detectable amount of alcohol in your system is illegal. This includes mouthwash or "non-alcoholic" beer.

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Traffic Signals and Lights

Understanding traffic signal meanings and proper responses is essential for safe driving and obeying traffic laws.

Standard Traffic Lights

Solid Red

Stop completely behind the stop line or crosswalk. Remain stopped until light turns green.

Solid Yellow

Caution — light is about to turn red. Stop if you can do so safely; otherwise proceed with caution.

Solid Green

Proceed when safe. Yield to vehicles and pedestrians still in intersection.

Arrow Signals

Green arrow — Protected turn. Oncoming traffic is stopped. You have right-of-way.
Yellow arrow — Protected turn is ending. Stop if safe to do so.
Red arrow — No turn allowed in that direction. Treat like solid red light.
Flashing yellow arrow — Permitted turn. Yield to oncoming traffic and pedestrians before turning.

Flashing Lights

Flashing Red

Treat as stop sign. Come to complete stop, yield to traffic, then proceed when safe.

Flashing Yellow

Proceed with caution. Slow down and be alert for hazards or cross traffic.

Red Light Right Turns

In most states, you may turn right at a red light after coming to a complete stop and yielding to all traffic and pedestrians, unless:

A "No Turn on Red" sign is posted
A red arrow is displayed instead of a solid red
Local law prohibits it (some cities/intersections ban all red light turns)

Malfunctioning Signals: If a traffic signal is completely dark or malfunctioning, treat the intersection as an all-way stop.

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Common Traffic Violations

Understanding common violations helps you avoid tickets, points on your license, and potential license suspension.

Moving Violations (Add Points to License)

Speeding — Fines increase with speed over limit. 20+ mph over can result in reckless driving charge.
Running red light/stop sign — Major violation, usually 3-4 points plus fines ($100-$500).
Improper lane change — Failure to signal, unsafe lane changes, crossing solid lines.
Following too closely (tailgating) — Must maintain safe following distance (3-4 seconds minimum).
Failure to yield — Not yielding to pedestrians, emergency vehicles, or vehicles with right-of-way.
Improper passing — Passing in no-passing zones, passing on right where illegal, passing school bus.
Reckless driving — Serious offense, potential license suspension and criminal charges.

Non-Moving Violations (Usually No Points)

Parking violations (illegal parking, expired meter, fire hydrant)
Equipment violations (broken taillight, missing mirror, illegal tint)
Registration/insurance violations (expired tags, no proof of insurance)
Seatbelt violations (driver and passengers not buckled)

Point System

Most states use a point system to track driving violations:

Minor Violations

2-3 points (speeding 10 mph over, improper turn, etc.)

Major Violations

4-6 points (reckless driving, DUI, hit and run, etc.)

License Suspension

Typically occurs at 12 points within 12 months (varies by state)

Point Reduction

Points usually expire after 1-3 years. Some states offer traffic school to reduce points.

Commercial Drivers: CDL holders face stricter violations and can lose their commercial license with fewer points or certain violations.

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Sample Practice Questions

Test your knowledge with these sample traffic law questions. The full quiz contains many more questions across all topics.

Question 1

You are driving on a highway with a posted speed limit of 65 mph. It begins to rain heavily. What should you do?

A) Maintain 65 mph since that's the speed limit
B) Reduce speed to match weather conditions
C) Increase speed to get through the rain quickly
D) Turn on hazard lights and continue at 65 mph

Answer: B — The basic speed law requires you to drive at a speed that is safe for current conditions, even if below the posted limit. Heavy rain reduces visibility and traction.

Question 2

At an intersection with a flashing red traffic light, you must:

A) Slow down and proceed with caution
B) Stop only if other vehicles are present
C) Stop completely, then proceed when safe
D) Yield to traffic on the right only

Answer: C — A flashing red light must be treated as a stop sign. You must come to a complete stop, yield to all traffic, and proceed only when it is safe to do so.

Question 3

What is the legal BAC (Blood Alcohol Concentration) limit for drivers under 21?

A) 0.08%
B) 0.04%
C) 0.02% or less (zero tolerance)
D) Same as adults, 0.08%

Answer: C — All states have zero tolerance laws for drivers under 21. Any detectable amount of alcohol (typically 0.00-0.02%) is illegal and results in license suspension and other penalties.

Question 4

Two vehicles arrive at an uncontrolled intersection at the same time. Which vehicle has the right-of-way?

A) The larger vehicle
B) The vehicle on the left
C) The vehicle on the right
D) Whichever vehicle arrived first

Answer: C — When two vehicles arrive simultaneously at an uncontrolled intersection, the vehicle on the right has the right-of-way. The driver on the left must yield.