Passing lane

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Diagram showing lanes and road layout, with Irish road markings.

A passing lane (North American English) or overtaking lane (British, Irish and Australian English) is the lane on a multi-lane highway or motorway closest to the center of the road (the central reservation). In Californian terminology, the passing lane is often known as the number one lane,[1] left lane, or leftmost lane, due to left hand drive (driving on the right), and the rightmost slow lane is sometimes called the "outside lane", because the lane nearest the center of the roadway is considered "inside". Some regions of the world reverse the definitions of "inside" and "outside", as described under #Regional terminology.

In modern traffic planning, passing lanes on freeways are usually designed for through/express traffic, while the outer lanes have entry/exit ramps. However due to routing constraints, some freeways may have ramps exiting from 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 through traffic or fast traffic. In theory, a passing lane should be used only for passing, thus allowing, even on a road with only two lanes in each direction, motorists to travel at their own pace.

Regional terminology[edit]

The official British Highway Code uses the term right hand lane, due to right hand drive (driving on the left). Unofficially, the overtaking lane is also called the outer or outside lane, since the edge of the road nearer to the verge (or nearer the hard shoulder, if there is one) is considered "inside" the other lanes. The lane nearest to the verge (or hard shoulder) is officially the left hand lane, or unofficially the "inner" or "inside lane".

The official Irish Rules of the Road use the term "Lane 1 (also known as the Inner Lane)" for the lane next to the hard shoulder. The overtaking lane is officially Lane 2 (also called "the outside lane") on a two-lane motorway, or Lane 3 on a three-lane motorway.

The Australian Road Rules use the terms left lane and right lane but in the opposite senses to American usage, due to right hand drive (driving on the left). Thus the overtaking lane is the right lane.

Note that in some other countries, like Hungary (driving on the right), the lane nearest to the centre of the road is considered "inside". Thus the passing lane is called the inner lane (belső sáv in Hungarian).


The use of the left lane for faster traffic is sometimes acknowledged with signs using phrases such as "Slower Traffic Keep Right"[2] (in Canada, where the passing lane is to the left). In a study by the AASHTO Subcommittee on Traffic Engineering, all 24 US states involved used some form of passing lane courtesy signage, 9 of which only use those signs for steep graded roads.[3]

Misuse and common practice[edit]

An SUV prepares to pass a slower moving car, using a passing lane in rural Utah
A car passes a slower moving truck, using a passing lane on the A2 motorway in Slovenia

Common practice and most law on United States highways is that the left lane is reserved for passing and faster moving traffic, and that traffic using the left lane must yield to traffic wishing to overtake. The United States Uniform Vehicle Code states:

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 ...

It is also illegal in many states in the US to use the "far left" or passing lane on a major highway as a traveling 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:

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...[4]

In Quebec, it is also illegal to travel in the left lane if you are not passing when the speed limit is over 80 km/h (50 mph).[5]

In other states, such as Massachusetts,[6] New Jersey,[7] Maine,[8] Illinois,[9] Pennsylvania,[10] and others,[11] it is 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, overtake 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.

A driver hoping to pass a slow motorist in the "fast lane" can be 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 is dangerous and illegal, is to drive very close to the "fast lane" driver's bumper (this is known as tailgating).

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 going too slowly in the passing lane. On 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.[citation needed]

In some areas, such as the US states of Colorado and Kentucky, vehicles in the left lane are required to yield to faster traffic only if the speed limit is above 65 miles per hour. In other areas, like Alaska, there is no law requiring slower traffic to move over for faster traffic.[11]

Proper use[edit]

Many areas which make it illegal to fail to yield to faster traffic, also have exceptions to those rules. Some of these exceptions include preparing to make a left turn, taking an exit located on the left side of the roadway, avoiding traffic merging onto the roadway, or overtaking and passing another vehicle.

Hammer lane[edit]

The hammer lane is another term for the passing lane. Its etymology originated with truckers in North America in reference to the action of a Hammer (firearm) causing a bullet to be fired from a gun. (It has nothing to do with slamming the accelerator with a foot like 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.

Climbing lane[edit]

Main article: Climbing lane

In hilly terrain, some standard highways (not dual carriageway) are built with three lanes, with the extra added pavement known as the "climbing lane" or "crawler lane". Two lanes are used for traffic heading in the uphill direction, with one lane being a passing or climbing lane, and one lane is used for downhill traffic. On dual carriageways, the climbing lane may be marked with a broken double white line.

Cultural references[edit]


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