If you are under age 21, Pennsylvania's laws do not permit you to drive with any measurable alcohol in your system. If you are under 21, you are considered to be driving under the influence if your blood alcohol level is 0.02 percent or greater.

Highway and expressway guide signs are green with white letters.

Pennant-shaped signs usually indicate no passing zones. Text will also be on the sign to confirm that it is a no passing zone.

The only situation during which you are not required to stop for a school bus that is stopped with its lights flashing and stop arm extended is if you are driving on the opposite side of a divided highway.

Driving at night is more dangerous than driving during the day for several reasons. It is harder to see in the dark, you may be temporarily blinded by the glare from other vehicles' lights, and there are likely to be more drivers on the road who are tired or under the influence.

White lines separate traffic lanes traveling in the same direction. You may cross broken white lines to pass, as long as the passing lane is clear.

It is against the law for anyone under 21 to buy or consume alcohol, have it in their possession, or have it in a vehicle that they are driving.

A flashing yellow light at an intersection means "caution." If you approach such a light, slow down, look, and proceed with care.

Drivers entering a roundabout or traffic circle must yield the right-of-way to drivers already in the circle.

Warning signs prepare drivers for upcoming road conditions and hazards and are usually yellow with black markings. This sign warns drivers that they are approaching a T intersection and should prepare to turn either right or left.

Emotions can have a great effect on your driving ability. You may not be able to drive well if you are overly worried, excited, afraid, angry, or sad. Stress can lessen your concentration on the task of driving. It is better to wait to drive than to risk driving while you are emotionally unstable.

The law does not give anyone the right-of-way at intersections; it only says who must yield. Even when one driver is legally required to yield the right-of-way, if they fail to do so, other drivers are still required to stop or yield as necessary to avoid a crash.

Always stop before entering the roadway from a driveway and yield to any approaching vehicles or crossing pedestrians. The stop should be made before crossing the sidewalk area. Failure to stop is unlawful.

When turning left at a traffic signal, you must yield the right-of-way to pedestrians and oncoming traffic.

Your tires become less effective at clearing water from the road as you increase your speed. If you drive too fast, they may lose their grip entirely, leaving the vehicle sliding on a film of water. This is known as "hydroplaning."

Yellow lines are used to separate traffic moving in opposite directions. Dashed lines indicate that drivers directly next to the line are permitted to pass when it is safe to do so.

When the flashing yellow lights on a school zone sign are activated, or during an indicated school zone time period, you may travel no faster than 15 mph.

You should always reduce your speed and use extra caution when children are in the vicinity. They may fail to understand the danger and may run out in front of you without looking.