DRTS Light-Vehicle Theory cheat sheet

Sign shapes carry meaning independent of text: octagon = stop, inverted triangle = yield, pennant = no-passing zone, diamond = warning, vertical rectangle = regulatory, horizontal rectangle = guide or information.

Sign colors: red = prohibitive or stop/yield; yellow = warning; fluorescent yellow-green = school, pedestrian, bicycle warning; orange = temporary work zone; white = regulatory; green = guide and permitted movement; blue = services and disability parking; brown = recreation and cultural.

A flashing red signal is treated as a stop sign: full stop, yield, then proceed when clear. A flashing yellow signal requires slowing and caution but no mandatory stop.

A steady circular green permits through and turning movements but does not by itself protect a left turn; a green arrow gives protected right-of-way for that movement.

Solid white lines separate traffic moving the same direction and should not be crossed; dashed white lines permit lane changes when safe. Solid yellow lines separate opposite directions and prohibit crossing; double yellow indicates no passing in either direction.

A red X over a lane means the lane is closed to your direction; a green arrow over a lane means the lane is open. A white steady left-pointing arrow over a lane may indicate a required turn.

Pavement markings: white crosswalk lines, yellow center lines, white stop bar before the crosswalk or intersection, and painted arrows indicating mandatory direction of travel.

Warning signs are placed in advance of the condition; the posted advisory speed on a yellow warning sign is the maximum recommended speed for the hazard, not a legal limit.

At an uncontrolled intersection, the first vehicle to arrive has the right-of-way; if two arrive at the same time, the vehicle on the left yields to the vehicle on the right.

A vehicle turning left must yield to oncoming traffic going straight or turning right, and to pedestrians in the crosswalk it enters.

A vehicle entering a roadway from a driveway, alley, or private road must yield to all traffic already on the roadway and to pedestrians on the sidewalk.

At a four-way stop, vehicles proceed in order of arrival; simultaneous arrivals resolve by yielding to the vehicle on the right.

A right turn on red is permitted after a full stop only where not prohibited by sign, and only after yielding to pedestrians and cross traffic.

Roundabouts: yield to traffic already circulating inside the circle, enter to the right, and do not stop inside the circle unless required by traffic.

Emergency vehicles with lights and siren have right-of-way; drivers must pull to the right and stop until the vehicle passes, and must not follow within 500 feet.

Pedestrians in a marked or unmarked crosswalk have the right-of-way; a driver must yield and may not pass a vehicle stopped at a crosswalk.

The basic speed law requires driving at a speed reasonable and prudent for conditions regardless of the posted limit; the posted limit is a maximum, not a target.

Three-second rule: watch the rear of the vehicle ahead pass a fixed object, count three seconds, and ensure your front bumper reaches that object no sooner. Add one second for each adverse condition (rain, darkness, heavy load, poor visibility).

At 55 mph, three seconds covers about 243 feet of travel; total stopping distance adds perception-reaction distance (about 1 second, roughly 60 feet at 55 mph) to braking distance.

Stopping distance grows with the square of speed: doubling speed roughly quadruples braking distance.

Common statutory limits: 15 mph in school zones or alleys (varies), 25 mph in residential or business districts, 55 mph on many two-lane rural roads, 65-70 mph on rural interstates unless posted otherwise.

Work zones with posted reduced limits are enforceable even when workers are absent; fines are commonly doubled for violations in work zones.

Minimum speed limits exist on some limited-access highways; driving unreasonably slowly impedes traffic and is a violation.

Following distance should increase behind motorcycles, large trucks, and vehicles carrying hazardous or loose loads, and in rain, fog, or snow.

Seat belts are required for the driver and all passengers in most jurisdictions; children under a specified age or height must use an approved child restraint in the rear seat.

A driver must signal intent to turn or change lanes continuously for at least 100 feet before the maneuver (more at highway speeds in some states).

Passing is prohibited on a solid yellow line, on hills and curves with limited sight distance, at intersections and railroad crossings, and where a no-passing pennant is posted.

A left turn on red is permitted only from a one-way street onto another one-way street, and only where local law allows it.

Drivers must stop for a school bus with flashing red lights and extended stop arm in both directions unless separated by a physical median or barrier.

Texting while driving is prohibited for all drivers in most states; many jurisdictions ban handheld phone use entirely and restrict novice drivers further.

Move Over laws require changing lanes or slowing when approaching stopped emergency, tow, or maintenance vehicles with lights flashing.

Headlights are required from sunset to sunrise, when visibility is reduced (commonly 500 feet or 1,000 feet in rain/fog), and whenever wipers are in continuous use in several states.

Tire tread must be at least 2/32 inch (1/16 inch) deep in most states; check with a penny inserted into the groove - Lincoln's head covered means tread is adequate.

Tire pressure should be checked cold and set to the vehicle manufacturer's placard value, not the maximum molded on the tire sidewall; pressure drops about 1 psi per 10°F drop in temperature.

Brake fluid absorbs moisture over time and should be flushed per manufacturer interval; a spongy pedal or sinking pedal indicates a hydraulic problem.

Headlights, taillights, brake lights, turn signals, and the horn are required equipment; a burned-out brake light is a common cause of rear-end collisions.

Windshield wipers and washer fluid must be functional; cracked windshields in the driver's line of sight are generally illegal.

Tire blowouts: grip the wheel firmly, ease off the accelerator, avoid hard braking, and steer to a controlled stop off the roadway.

Engine overheating: turn off the air conditioner, turn on the heater to draw heat from the engine, and stop safely; never open a hot radiator cap.

Jump-starting order: connect positive to positive first, then negative to a bare metal ground on the dead vehicle, not to the battery terminal.

Bicycles are vehicles with the same rights and duties as cars; drivers must give at least 3 feet of clearance when passing a cyclist in most states.

Motorcycles are entitled to a full lane; a motorcycle's small profile makes speed and distance judgments harder, so allow a larger following gap.

Large trucks have large blind spots (No-Zones) on both sides, directly behind, and in front; if you cannot see the truck driver's mirror, the driver cannot see you.

Trucks need far more distance to stop and swing wide when turning right; never pass a truck on the right when it is preparing to turn.

Pedestrians: yield at crosswalks; at night a pedestrian in dark clothing may be visible only about 200 feet ahead in low beams.

School zones require reduced speed during posted hours; watch for children who may enter the roadway unpredictably between parked cars.

When passing a horse-drawn vehicle or someone on horseback, slow down and give wide clearance; horses may spook at engine noise.

Leave extra room for vehicles displaying a slow-moving vehicle triangle (orange triangle with red border), which travel at 25 mph or less.

Scan 12-15 seconds ahead in urban driving and 20-30 seconds on the highway; check mirrors every 5-8 seconds to maintain a full picture.

The Smith System: Aim High in Steering, Get the Big Picture, Keep Your Eyes Moving, Leave Yourself an Out, Make Sure They See You.

Space cushion: maintain at least a 2-second gap, 3 seconds at higher speeds, and position the vehicle so an escape route exists on at least one side.

Hydroplaning occurs when water depth and speed lift tires off the pavement; it can begin around 35 mph on wet roads. Ease off the accelerator and avoid braking hard.

Black ice forms first on bridges, overpasses, and shaded areas; the road may look merely wet. Reduce speed before reaching the bridge.

Fog: use low beams, not high beams, which reflect off the moisture and reduce visibility; reduce speed and increase following distance.

Skids: ease off the accelerator and steer in the direction you want the front of the vehicle to go; avoid slamming the brakes.

Distraction and fatigue: drowsy driving produces impairment comparable to alcohol; symptoms include lane drifting, missed exits, and difficulty focusing. Stop and rest.

The national illegal per se limit is 0.08% blood alcohol concentration (BAC) for drivers 21 and older; a lower limit of 0.00-0.02% applies to drivers under 21 under zero-tolerance laws.

Commercial drivers are held to a 0.04% BAC limit in most jurisdictions.

Alcohol is eliminated at roughly 0.015% BAC per hour; nothing - coffee, cold showers, food - speeds this rate.

Impairment begins below 0.08%: at 0.05% BAC, judgment, alertness, and coordination are already measurably reduced.

Implied consent laws require submitting to a chemical test when lawfully arrested for DUI; refusal typically triggers license suspension and can be used as evidence.

Prescription and over-the-counter drugs, including antihistamines and sleep aids, can impair driving; combining them with alcohol multiplies the effect.

Standard field sobriety tests include the horizontal gaze nystagmus, walk-and-turn, and one-leg stand; they estimate impairment but do not measure BAC.

Fatigue, illness, and untreated vision problems are driver-fitness hazards; a driver who cannot stay in lane should not be driving at all.