In North American terminology, the passing lane is often known as a left lane or leftmost lane, due to left hand drive (driving on the right). In British/Irish terminology, the passing lane is termed an outer lane or outside lane, while a normal lane nearer the hard shoulder is termed an inner lane (or inside lane). Note that in some other countries, like Hungary and Australia, the passing lane is called the inner lane (belső sáv in Hungarian), because this lane is the closest to the middle of the road, thus it is the innermost.
In modern traffic planning, passing lanes on freeways are usually designed for through/express traffic, while the inner lanes have entry/exit ramps. However, many freeways often have ramps on the passing lane, these are known as "left exits" in North America.
A passing lane is often colloquially referred to as a fast lane because it is often used for extended periods of time for thru traffic or fast traffic. In theory, a passing lane should only be used for passing, thus allowing, even on a road with only two lanes in each direction, motorists to travel at their own pace. Good driving practice is to slip out of the passing lane once slower cars have been passed.
Upon all roadways any vehicle proceeding at less than the normal speed of traffic at the time and place and under the conditions then existing shall be driven in the right-hand lane then available for traffic ...The Massachusetts Institute of Technology's website on "Keep Right Laws" points out that:
It is also illegal in many states in the U.S. to use the "far left" or passing lane on a major highway as a travelling lane (as opposed to passing), or to fail to yield to faster moving traffic that is attempting to overtake in that lane. For example, Colorado's "Left Lane Law" states:This law refers to the "normal" speed of traffic, not the "legal" speed of traffic. The 60 MPH driver
A person shall not drive a motor vehicle in the passing lane of a highway if the speed-limit is sixty-five miles per hour or more unless such person is passing other motor-vehicles that are in a non-passing lane...(emphasis added)
Other examples, such as Massachusetts (General Statute 89-4B), New Jersey, Maine, Illinois, Pennsylvania, and others, make it illegal to fail to yield to traffic that seeks to overtake in the left lane, or to create any other "obstruction" in the passing lane that hinders the flow of traffic. As a result, heavy trucks are often prohibited from using the passing lane.
A common problem arising from misuse of the "fast lane" is that it forces faster moving traffic that wishes to overtake on the left to change lanes, do so on the right, and then change lanes again. Further, if the vehicle misusing the passing lane is going slower than the flow of other traffic, it forces those using the middle "travel" lane (but who are moving faster) to pass on the right as well, even though they have no intention of doing so.
A driver hoping to pass a slow motorist in the "fast lane" is stuck in an awkward situation. One strategy is to signal a lane change toward the center median. Another is to flash headlights. A third, which sacrifices safety, is to drive very close to the "fast lane" driver's bumper (this is known as tailgating). In Germany it is common to signal a lane change toward the center of the road, as if there where another lane to the left of the "fast lane".
Most commonly, motorists will attempt to overtake the outer car on the inner lane either to continue at a fast pace or to pass a car that is simply going too slow in the passing lane. For high-capacity multilane freeways (three or more lanes per direction), many motorists often pass on the inner lane, largely in response to misuse of the "passing lane" by slower traffic.
The hammer lane is another term for the passing lane. Its etymology originated with truckers in North America and compares a foot pressing hard on an accelerator pedal with the slamming action of a hammer. Truckers often use the hammer lane in moderate traffic, where it is legal to do so, since they travel long distances. In many areas, tractor trailers are banned from using the hammer lane for safety reasons; these restrictions are normally found along urban, often congested highways with multiple lanes (e.g. Interstate 40 west of Raleigh, North Carolina), or on rural freeways with 6 or more lanes (3 in each direction). HOV lanes are not usually considered hammer lanes, but are also used for express travel by commuters.