Overtaking other vehicles is sometimes considered as American as apple pie, encompassing the urge to win, to get to the front of the line, to be first among equals. And sometimes you just need to pass because the car ahead of you is going 20 miles under the speed limit. So, should you pass? That depends on the rules of the road, the traffic, the terrain and the weather.
Illegal to Pass
Passing is not always permitted, especially on two-lane roads. If you aren't up on the road markings that indicate when passing is allowed, take a moment to review them. If the center line is a double solid yellow line, neither side can pass. If there is a solid yellow line on your side, you cannot pass. If the other side has a solid yellow line, drivers going the other way cannot pass. And it's always illegal to pass if there is a "Do Not Pass" sign on the roadway.
It's also illegal to pass cars going at or very near the speed limit. That's because you will have to exceed the speed limit when you pass. Despite rumors to the contrary, state laws do not make an exception to the posted speed limit for passing. An individual officer may or may not give you a break in that case, but she isn't required to.
On a street or highway with two-way traffic, you should pass only on the left. In some states, like California, it is illegal to pass on the right unless you are on a one-way street or you are on an open highway clearly marked for two or more lanes of travel in your direction. Don't ever use the shoulder to pass.
Dangerous to Pass
It is dangerous to pass, and may be illegal in some states, when the terrain makes it difficult to see the roadway ahead. Even if the roadway is not marked with double yellow lines, you should never pass another vehicle when you are approaching a curve or topping a hill unless you have a very clear view of the road ahead. Often you won't be able to see oncoming traffic at a sufficient distance to assess whether you can pass safely.
It is likewise dangerous and sometimes illegal to pass within 100 feet of a bridge or railroad crossing, or when the vehicle ahead is a school bus that is loading or unloading children.
Oncoming traffic affects your right (as well as ability) to overtake the vehicle ahead of you. And it's always dangerous to try to pass a long line of cars.
Weather Changes Traffic Rules
Bad weather can make driving maneuvers dangerous that would otherwise be safe. In most states, the posted speed limits and traffic signs are not the end-all and be-all. The ultimate rule is that you must drive safely for road conditions. So, passing another vehicle at 65 mph in heavy fog or torrential rain may be breaking the law, even if you are in a zone posted for 65 mph.