Main line (railway) in the context of "Great Western Main Line"

Commuter rail or suburban rail is a passenger rail service that primarily operates within a metropolitan area, connecting commuters to a central city from adjacent suburbs or commuter towns. Commuter rail systems can use locomotive-hauled trains or multiple units, using electric or diesel propulsion. Distance charges or zone pricing may be used.

The term can refer to systems with a wide variety of different features and service frequencies, but typically refers to mainline rail services connecting suburban communities with city centres over medium distances; it is distinguished from rapid transit systems which operate inside the urban core.

A tram (also known as a streetcar or trolley in Canada and the United States, or a Tramcar) is an urban rail transit type in which vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some include segments on segregated right-of-way. Trams are a variant of light rail and are included within this broader category. However, they differ from it in their frequent integration into urban streets, lower traffic signal priority, coexistence with other vehicles, and lower capacity. Their units are capable of forming motor coaches or motorcars, which allows for the operation of longer trains.

Trams are usually lighter and shorter than main line and rapid transit trains. Most trams use electrical power, usually fed by a pantograph sliding on an overhead line; older systems may use a trolley pole or a bow collector. In some cases, a contact shoe on a third rail is used. If necessary, they may have dual power systems—electricity in city streets and diesel in more rural environments. Occasionally, trams also carry freight. Tramlines or tram networks operated as public transport are called tramways, or simply trams or streetcars, including systems separated from other traffic. Some trams, known as tram-trains, may have segments that run on mainline railway tracks, similar to interurban systems. The differences between these modes of rail transport are often indistinct, and systems may combine multiple features.

A branch line is a secondary railway line which branches off a more important through route, usually a main line. A very short branch line may be called a spur line. Branch lines may serve one or more industries, or a city or town not located on a main line. Branch lines may also connect two or more main lines.

A refuge siding is a single-ended, or dead-end, siding off a running line, which may be used to temporarily accommodate a train so that another one can pass it. For example, a refuge siding might be used by a slow goods train to allow a fast passenger train to pass. It is similar in concept to a passing loop but is connected to the main line at only one end, rather than both ends.

A tram (also known as a streetcar or trolley in Canada and the United States, or a Tramcar) is an urban rail transit type in which vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some include segments on segregated right-of-way. Trams are a variant of light rail and are included within this broader category. However, they differ from it in their frequent integration into urban streets, lower traffic signal priority, coexistence with other vehicles, and lower capacity. Their units are capable of forming motor coaches or motorcars, which allows for the operation of longer trains.

Trams are usually lighter and shorter than main line and rapid transit trains. Most trams use electrical power, usually fed by a pantograph sliding on an overhead line; older systems may use a trolley pole or a bow collector. In some cases, a contact shoe on a third rail is used. If necessary, they may have dual power systems—electricity in city streets and diesel in more rural environments. Occasionally, trams also carry freight. Tramlines or tram networks operated as public transport are called tramways, streetcars or simply trams, including systems separated from other traffic. Some trams, known as tram-trains, may have segments that run on mainline railway tracks, similar to interurban systems. The differences between these modes of rail transport are often indistinct, and systems may combine multiple features.

Automatic train operation (ATO) is a method of operating trains automatically where the driver is not required or is required for supervision at most. Alternatively, ATO can be defined as a subsystem within the automatic train control, which performs any or all of functions like programmed stopping, speed adjusting, door operation, and similar otherwise assigned to the train operator.

The degree of automation is indicated by the Grade of Automation (GoA), up to GoA4 in which the train is automatically controlled without any staff on board. On most systems for lower grades of automation up to GoA2, there is a driver present to mitigate risks associated with failures or emergencies. Driverless automation is primarily used on automated guideway transit systems where it is easier to ensure the safety due to isolated tracks. Fully automated trains for mainline railways are an area of research. The first driverless experiments in the history of train automation date back to 1920s.

A rail yard, railway yard, railroad yard (US) or simply yard, is a series of tracks in a rail network for storing, sorting, or loading and unloading rail vehicles and locomotives. Yards have many tracks in parallel for keeping rolling stock or unused locomotives stored off the main line, so that they do not obstruct the flow of traffic. Cars or wagons are moved around by specially designed yard switcher locomotives (US) or shunter locomotives (UK), a type of locomotive. Cars or wagons in a yard may be sorted by numerous categories, including railway company, loaded or unloaded, destination, car type, or whether they need repairs. Yards are normally built where there is a need to store rail vehicles while they are not being loaded or unloaded, or are waiting to be assembled into trains. Large yards may have a tower to control operations.

Many yards are located at strategic points on a main line. Main-line yards are often composed of an up yard and a down yard, linked to the associated direction of travel. There are different types of yards, and different parts within a yard, depending on how they are built.