Have you ever been driving on the road only to be scared half out of your skin by a car that zooms past you like you are standing still? Or, have you ever been on the road and realize that you’re about to run right over a car that’s going so slowly you’re sure the occupants could get to their destination faster by walking?

Both situations are common enough, and they’re both against the law. Maryland has specific laws that require drivers to maintain a safe speed. That’s a speed that is neither too fast — nor too slow — for the circumstances.

What exactly does that mean? Well, that’s where things can get somewhat complicated and confusing for drivers.

Generally speaking, there’s no trick to understanding how the absolute maximum speed limit works: You can’t drive faster than the posted speed limit. There are times, however, where the maximum safe speed you can drive is actually a lot slower than what’s posted. For example, if the roads are icy and snow is coming down, it’s not really safe to travel 60 mph down the highway. At times, it’s necessary to use your best judgment.

On the other hand, you also can’t go too slow without putting yourself and others in danger. For example, some drivers panic when they get in a construction zone that is guarded on all sides by concrete barriers. They may creep along, creating a real hazard for everyone. Anything less than 10 mph below the posted speed limit is usually too slow — unless there are weather conditions or some additional reason that makes it unsafe to drive a normal speed.

Defending against a ticket based on speed isn’t impossible. Sometimes, you can prove that you had a valid reason for exceeding the speed limit (or going much slower than normal). Other times, you may be able to contest the officer’s identification of your vehicle. For example, maybe an officer used a radar gun to clock a speeder in traffic but pulled you over by mistake. If you believe you’ve wrongly received a traffic ticket based on speed, an attorney can protect your interests in court.