Shoulder (road) - General Characteristics

General Characteristics

The shoulder is usually slightly narrower than a full traffic lane. In some cases, particularly on old rural roadways, shoulders do not exist or are made of gravel rather than hard asphalt or concrete. These are known as soft shoulders in comparison. Because the road surface changes at that point, they are less safe if they need to be used for emergency maneuvers, so modern practice is to build a hard shoulder whenever possible.

To save money, the hard shoulder is sometimes not paved to the same thickness as the through lanes, so if vehicles were to attempt to use it as a through lane regularly, it would rapidly deteriorate. The shoulder also often collects various bits of road debris that can make driving there unsafe.

Drivers will sometimes drift into the shoulder when being overtaken by passing vehicles, particularly on two-lane roads. However, it is extremely unsafe, as well as often illegal, to abuse the hard shoulder by 'undertaking' passing vehicles that are nearer the centre of the road. (Some roads and expressways have a hard shoulder that is of such a narrow width that 'undertaking' is impossible.)

On many roads, the shoulder disappears for short periods, particularly near exits and sometimes when going across or under bridges where the cost savings outweigh the disadvantages of not having the shoulder. However, some roads have a narrow shoulder for significant distances. This makes it difficult for large vehicles to pull into the hard shoulder altogether.

The Jingjintang Expressway in northeastern China is an example of this phenomenon. Its hard shoulder is 2.4 metres wide, which is not wide enough for some automobiles. As a result, some motorists are unable to fully exit the mainline when they need to pull over, so they end up in a position that is halfway in the rightmost lane and halfway in the hard shoulder. The result is often a traffic jam and occasionally a collision.