Road signs and markings are the driver's lingua franca. Everything about them conveys an important message-not just the words, but also their shape, color and placement.

"Road signs and pavement marking are the most important way engineers have to convey information, provide guidance for motorists and warn them of impending hazards," says Mark Kulewicz, the Club's director of Traffic Engineering and Safety Services. "Engineers try to pack as much information into them as possible, so the shapes, symbols and everything else help convey the meaning."

After driving for years, you probably think you know everything you need to know about road signs and markings. But do you, really? Take our quiz and find out.

1. On a Sunday evening, you're driving home after a weekend ski trip. It's getting late-at least three hours after sunset. You're tired. You're running low on gas. You notice a sign saying "Gas-Exit 44," with the logo of a service station. What won't you find there?

A. A pay phone
B. Public rest rooms
C. A sign saying, "Closed on Sundays."
D. A sign saying: "Winter hours: 7 a.m.- 11 p.m."

"Businesses pay a fee to be on those 'Gas,' 'Food' and 'Lodging' signs at exits," says Kulewicz, who also served on the committee that drafted the federal guidelines for tourist information signs. "But they have to meet certain requirements." Gas stations, for example, must be no more than 3 miles from the exit and offer public rest rooms, drinking water and pay phones in addition to fuel. They also must stay open at least 16 hours a day, seven days a week, on freeways and expressways. So you can be absolutely sure that you'll never see a "Never on Sunday" sign (C).

2. On the same ski trip, you notice a round sign alongside a two-lane road. Recent snowfall has stuck to the sign, completely obscuring its lettering and color. You can make out only its shape-a perfect circle. What should you do?

A. Proceed cautiously and prepare to stop.
B. Refrain from parking alongside the road.
C. Start fishing for change to pay a toll.
D. Watch out for livestock crossing ahead.

As you learned way back in driver's ed class, a sign's shape helps convey its meaning. On U.S. roads, four shapes have specific, unique meanings: the familiar octagon only means stop; the X, or cross-buck, always identifies a railroad crossing; the pennant, or isosceles triangle pointing to the right, always identifies a no-passing zone in construction areas; and the only round sign is the railroad advance warning sign. It's yellow, with a big black X between the letters "RR." You'll find it as you approach railroad tracks, in advance of the X-shaped sign, at the crossing itself.

In this case, you should slow down and prepare to stop in case a train is approaching (A). By the way, if you answered "B," give yourself credit for a nice try. You'll find a red circle with a slash through a "P" at places where you're not allowed to park; similar circles and slashes prohibit bicycles, U-turns and such. But you'll always find them on a square sign.

3. Late one night, on a winding rural road with no street lamps, this sign looms ahead of you in the dark: a tall, skinny rectangle with alternating yellow and black stripes, slanting down to the left. Without looking at the edge lines or anything else, you know immediately you should:

A. Drive to the right of the sign.
B. Drive to the left of the sign.
C. Stop immediately; the road is about to end.
D. Wonder, "What's a funny-looking barber pole doing way out here?"

You've encountered what traffic engineers call an "object marker," warning of a bridge abutment or some other intrusion in the roadway. Its slanted lines always point down toward the lane you're supposed to follow-in this case, the left (B). Similar slanted lines guide you around construction zone barriers.

4. Taking a cross-country drive, you get on I-22 at Exit 35 and get off at Exit 151. In what direction are you traveling?

A. West.
B. East.
C. South.
D. Toward the Presidential ranch, where the Secret Service has renumbered the exits for security purposes.

After living in New York State for so many years, you might not have noticed that most other places follow federal guidelines and number their exits according to mile markers. On even-numbered Interstates, mile markers begin in the west and increase as you move east; on odd-numbered Interstates, the mile markers begin in the south and increase as you move north.

On our fictional I-22, going from Exit 35 to Exit 151, you'd be traveling east (B). New York State, which numbers its exits consecutively west to east and south to north without regard to mile markers, is only one notable exception to this rule. California, which for some reason doesn't number its exits at all, is another.

5. On a dark, foggy night in an unfamiliar part of town, you're looking for the entrance ramp to the highway. When you finally find it and make the turn, you notice these edge lines: a continuous white line on the left and a continuous yellow line on the right. You should:

A. Proceed cautiously.
B. Accelerate quickly to highway speed.
C. Turn around.
D. Regret that you didn't ask for directions at the gas station you passed a mile back.

Whoa! Yellow edge lines always separate traffic traveling in the opposite direction or mark the left edge of the highway. If you ever see them on your right, you're headed directly into opposing traffic. White edge lines always delineate the right edge of the roadway; they should always be on your right. In this case, you've mistakenly turned onto an exit ramp. Stop immediately and turn around (C).

6. While passing another car on a highway, you notice painted tick marks protruding about two feet from the edge line to the left. They seem regularly spaced, every few hundred feet or so. You should:

A. Plan another route for the way home.
B. Check your speedometer.
C. Begin counting the marks and check your odometer for accuracy.
D. Keep your eyes peeled for hitchhikers along the left side.

It wouldn't be a bad idea to glance at your speedometer and make sure you're at or under the legal limit (B). Big Brother may be watching from above. Those tick marks, known as "speed measurement markings," help law enforcement time a vehicle's travel over a given distance and catch speeders. Think of them as primitive radar guns. Airborne officers in particular find them helpful.

7. You're driving in a quiet residential neighborhood in New York City when you encounter a series of horizontal white lines on the pavement, forming the pattern shown at left. You respond by:

A. Bracing yourself to roll over rumble strips ahead.
B. Pulling to the side quickly to avoid oncoming traffic.
C. Preparing to reduce your speed.
D. Reporting graffiti artists to local authorities.

The series of gradually lengthening lines signal a speed bump or other traffic-calming device ahead, so you should prepare to slow down (C). You shouldn't be going fast in the first place. The speed bump itself may be marked by a series of small triangles nested inside large chevrons, pointing in the direction of traffic flow.

8. On a multi-lane urban expressway, a single, solid white line separates lanes of traffic moving in the same direction. You're driving in the center lane. Suddenly, the single white line on your left turns into a double white line. Under what circumstances may you move to the left lane?

A. Anytime.
B. Never.
C. Only when you have a safe gap in traffic to your left.
D. During nonrush hours, as specified by signs.

If you answered anything but B, you could find more trouble than you bargained for. Crossing a double white line is not just illegal; it's downright dangerous.

White lines always separate traffic streams moving in the same direction. Single ones are often used at the beginning of exit or entrance ramps or in areas where road construction forces lanes to shift positions; they discourage lane changing, but don't strictly prohibit it. Double white lines, on the other hand, forbid lane changes. Cross them at the risk of a ticket or some greater peril. For example, double white lines are often used to divert traffic around obstacles in the roadway. Locally, you might have noticed them on the Verrazano Narrows Bridge into Brooklyn (where they separate traffic headed either for the Gowanus Expressway or Belt Parkway) or on the Belt Parkway in Queens (where they divert traffic around bridge supports).

9. You're preparing to turn right at a big-city intersection. The traffic light has a red arrow pointing right. Since there are no cars coming on the cross street, the guy behind you starts blowing his horn, urging you to exercise your right-turn-on-red option. You should:

A. Wait for the light to turn green.
B. Turn right on red after stopping.
C. Give up, go straight, and turn right at the next intersection.
D. Flip the bird at the guy blowing his horn.

In roadway math, one red arrow pointing right equals one no-turn-on-red sign. Despite what the guy behind you thinks, you must legally wait for a green light (A).

10. You're on a two-way neighborhood street. In mid-block, you see a row of short, evenly spaced parallel white lines stretching across the roadway. You should:

A. Prepare to yield to pedestrians.
B. Stop immediately before crossing the lines.
C. Prepare to yield to a trolley or other light-rail transport.
D. Make a mental note to have your glasses checked.

Typically, this pattern identifies a crosswalk at mid-block or other location where there isn't a traffic light or stop sign. Consequently, you should prepare to yield to pedestrians when they step off the curb-whether they're coming from the right- or left-hand side of the street (A).

Why doesn't this crosswalk design include two long, transverse white lines typical of other crosswalks?

Those long lines across the road, explains Kulewicz, require repainting more often as thousands upon thousands of tires roll over them every day. In this case, painting only the "rungs" of the ladder and omitting its sides mean fewer return trips for maintenance crews-which only proves that there's more to designing road signs and markings than meets the eye.