Signs, Signals and Markings: Eight Sign Colors and Their Meanings, the Shapes You Must Know at a Distance, Damaging a Sign as a Misdemeanor or Felony, Stop, All-Way, Yield and the Red Circle, Regulatory Signs From School Zones and Lane Controls to Center Lane Only, Keep Right, Do Not Pass and No Trucks, Yellow Warning Signs for Signals, Divided Highways, Low Clearance, Merges, Lane Ends, Hills, Deer, Bridges and Pedestrians, Reflectors and Barricade Stripes, Railroad Advance Signs and Stopping 15 to 50 Feet Back, Crossbucks, Flashing Lights, Gates and Quiet Zones, Orange Work Zone Signs With Double Fines, Flagpersons and Channeling Devices, the Slow-Moving Vehicle Emblem, Guide, Milepost and Service Signs, Every Traffic Light and Arrow, Turns on Red, Pedestrian and Lane Control Signals, and Yellow and White Lines

Written for aiforu2 as the source for a practice-test bank and the on-device tutor for the Oklahoma Class D driver license written test. The facts follow the official manual; the wording is ours.

Source: Oklahoma Driver Manual (Service Oklahoma, November 2025), Chapter 4 "Signs, Signals and Markings" (pages 19–27).

Colors, shapes and the basic signs

Signs tell you about the road, the highway system, traffic flow and local laws, warn of hazards, identify routes and direct speed and movement, from the big green overhead interstate signs to the small blue rectangles pointing to a library or hospital. Learn the standard colors and shapes so you know a sign's meaning at a distance or even when it is damaged or covered by snow: a red octagon always means stop, a rectangle is always regulatory. Red means stop or "not allowed"; orange construction and maintenance warning; yellow general warning; fluorescent yellow-green high-emphasis warning for schools, pedestrians and bicycling; white with black regulations and instructions; green guide; blue driver guidance and services; brown recreation, culture and history. Obstructing or damaging roads, or defacing, damaging, destroying or removing any traffic control device, sign or post, is a misdemeanor, and if it causes injury or death a felony punishable by up to two years in prison and a $1,000 fine. The stop sign, a red octagon, requires a complete stop at the intersection, before the pedestrian crosswalk even if it is unmarked, staying stopped until the way is clear in all directions; a red 4-Way or All-Way rectangle below it means every approach must stop. The yield sign, a red-and-white triangle, means slow, be ready to stop and let oncoming vehicles pass before crossing or entering the flow. A red circle with a line through it means "do not" or "not allowed."

Regulatory signs

Regulatory signs, black-and-white rectangles, tell you what you must and must not do, and you obey them like any law. A School Zone sign requires slowing to the limit shown when the yellow light flashes, watching for children and being ready to stop. Lane control signs show which movements each lane may make: for example one lane must turn left while the next may go left or straight, one lane must go straight while the next may go right or straight, a lane that must turn left, or a lane with no turns allowed. Center Lane Only means enter the center lane only to make a left turn and never pass in it. The Speed Limit sign gives the highest speed allowed under ideal conditions. Do Not Enter means the road ahead carries one-way traffic coming toward you. Keep Right directs you to the right of an object or center divider. Do Not Pass forbids passing and crossing the yellow lines because you cannot see far enough ahead. Other common signs forbid right turns, U-turns (turning around in the street or intersection), trucks and bicycles. The international symbol for the disabled marks parking reserved for disabled people, which you may not use without a disabled plate or placard.

Warning signs

Warning signs are yellow diamonds with black letters that signal conditions immediately ahead, such as hazards or changes of direction, calling for extra caution: a traffic signal ahead (be ready to stop); a divided highway ending (two-way traffic resumes); low clearance (vehicles or loads taller than the figure cannot pass under); a gentle curve (slow, keep right, do not pass); a divided highway ahead with a median (keep right); two-way traffic ahead (drive in the right lane and expect oncoming traffic on the left); two roads joining with a new lane added (no need to merge, but watch the new lane); merge (other traffic may enter your lane, so be ready to change speed and lane so others can merge safely); right lane ends (prepare to merge); steep hill (approach with caution, perhaps in a lower gear); deer crossing; stop sign ahead; a narrow two-lane bridge or culvert; and pedestrian crossing (slow, prepare to stop, watch both sides and yield). Fluorescent yellow-green school signs mark school zones and school crossings. Reflectors mark objects near the road edge such as culverts and center piers, show road alignment at night, stand before obstructions and short alignment changes, and sit on the end rails of narrow bridges. A T-intersection sign means you must turn right or left and be ready to yield. On a striped warning sign or barricade, stripes sloping down to the right mean bear right and stripes sloping down to the left mean bear left, showing which side traffic passes.

Railroad, work zone and slow-vehicle signs

The round yellow-and-black railroad advance sign tells you tracks are ahead: slow and be ready to stop within 15 to 50 feet of the first track, drive very slowly if your view is blocked until you can see down the track, and stop if a train is coming. School buses, church buses, motor coaches and vehicles hauling explosives or flammable liquids must stop at crossings, and you may not pass a vehicle that is required to stop except on a multi-lane highway. Crossbucks stand at most crossings: slow, look, listen and be ready to yield to a train, and a plaque gives the number of tracks where there is more than one. Flashing lights on a crossbuck mean a train is coming; stop and stay stopped until it has passed, checking that every track is clear at a multi-track crossing. With a gate, stop when the lights start flashing and before the gate comes down, and stay stopped until the gates rise and the lights stop. Quiet Zones, marked by a "No Train Horn" sign, are crossings where trains do not sound their horns in normal operation, though engineers may still sound them in emergencies or for safety, and such crossings may have extra safety measures funded by local governments. Orange means a work zone: signs, barricades and channeling devices such as cones and barrels guide you through and protect workers and flagpersons; most signs are diamonds, some rectangles; you must slow to the posted speed, and speeding fines are doubled in a construction or maintenance zone when workers or equipment are present; be ready to slow or stop, change lanes, follow instructions and react quickly. Flashing arrow panels guide you into the proper lane, showing a move left or a closed lane. Flagpersons stand in the road in orange hats and orange vests, shirts or jackets, holding red signs or flags, and the law requires obeying them: when told to stop, stop in your lane without veering, do not move until signaled, then proceed with caution expecting workers and machinery and watching for oncoming vehicles in your lane. Channeling devices include barricades, panels, cones and drums. Failing to obey construction and maintenance signs, signals and markings is a misdemeanor punishable by a fine of $100 to $1,000 and/or up to 30 days in jail plus liability for damage, injury or death. The slow-moving vehicle emblem marks agricultural, construction and highway maintenance equipment traveling at 25 mph or less.

Guide and service signs

Guide signs, in green, white or brown, identify highways, show distances, mark exits and point to parks and recreation areas. A business route sign marks an officially designated highway that branches from the numbered route through a city's business district. Mileposts mark every mile of an interstate starting at the state line, numbered from the southern line on north-south highways and the western line on east-west highways, and they locate collisions and breakdowns for emergency calls. Green interstate guide signs are usually mounted overhead, with arrows showing the lanes for a given highway. Blue service signs give information and directions about service stations, restaurants, motels and hospitals, and the litter barrel sign marks the only lawful place on the highway to throw trash, found at all rest and picnic areas and turnpike toll stations; the state litter hotline is 1-888-5-LITTER.

Traffic signals

Signals control vehicles and pedestrians at intersections by granting the right-of-way in each direction, and you obey them except when an officer directs traffic, whom you always obey. Color-blind drivers read position: red on top, yellow in the middle, green at the bottom. Adjust your speed approaching an intersection so you can slow or stop if the light changes, and even on green yield when yielding will prevent a collision, even if the other person is wrong. Green: go, crossing or turning where turns are allowed, after making sure the intersection is clear and watching for drivers racing to beat a red light. Steady yellow: the light is about to turn red; stop if you can stop safely before entering the crosswalk, adjusting speed for a smooth stop, never speeding up to beat it, since collisions often happen here. Red: come to a complete stop before the crosswalk or intersection and stay stopped until green; after a complete stop you may turn right on red, and left from a one-way street into a one-way street, unless signs forbid it, yielding to all pedestrians and vehicles using the intersection, including bicycles. Green arrow: you may turn in the arrow's direction even while the red light is on; in a turn-only lane you must wait for the arrow, you may make only the movement shown unless signs say otherwise, and with turn lanes you must be in the proper lane. Enter cautiously, yielding to pedestrians in the crosswalk and vehicles legally in the intersection. Flashing yellow arrow: reduce speed and cautiously turn left after yielding to oncoming traffic and pedestrians, since oncoming traffic has the right-of-way. Flashing red: used at dangerous intersections where cross traffic may not stop, it means the same as a stop sign, so go when it is safe to cross. Red arrow: all turns in the arrow's direction are prohibited until a green signal. Flashing yellow: caution, slow, look both ways and drive slowly and carefully through, ready to stop. Pedestrian signals, Walk and Don't Walk, direct and protect people crossing on foot or in wheelchairs, who obey them instead of the traffic signal: Walk means leave the curb and cross; a flashing Don't Walk means do not leave the curb but finish if already in the intersection; a steady Don't Walk means do not leave the curb. Lane control signals over reversible lanes show a red X (do not use the lane), a yellow X (clear the lane, or when flashing, a left turn is permitted) and a green arrow (lane open).

Pavement markings

Yellow and white markings regulate traffic, showing which lane to use, where visibility is limited and passing is dangerous, where traffic in the next lane comes toward you, and where you may safely wait to turn left. A broken yellow line marks two-lane, two-way traffic where passing is permitted. A solid yellow line in your lane means do not pass: two solid yellow lines forbid passing in either direction, and the center line may be crossed only to turn left; a solid line beside a dashed line forbids passing for the lane with the solid line.

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