Rail transport operations
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A railway can be broken down into two major components. Basically these are the items which "move", the rolling stock, that is the locomotives, passenger carrying vehicles (coaches), freight carrying vehicles (goods wagons/freight cars) and those which are "fixed", usually referred to as its infrastructure. This category includes the permanent way (tracks) and buildings (stations, freight facilities, viaducts and tunnels).
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[edit] Operation
The operation of the railway is through a system of control, originally by mechanical means, nowadays, in most places, electronic and computerized. There are two main types or systems used to control the movement of traffic, fixed block signal and moving block signal (US) (absolute block and track circuit block (UK)).
[edit] Intrinsic factors
[edit] Signals
Fixed block signal
Most blocks are 'fixed' blocks, i.e. they delineate a section of track between two defined points. On timetable, train order, and token-based systems, blocks usually start and end at selected stations. On signalling-based systems, blocks start and end at signals.
The lengths of blocks are designed to allow trains to operate as frequently as necessary. A lightly-used branch line might have blocks many kilometres long, whilst a busy commuter railway might have blocks a few hundred metres long.
Moving block signal
A disadvantage of fixed blocks is that the faster trains are permitted to run, the longer the stopping distance, and therefore the longer the blocks need to be. This decreases a line's capacity.
With Moving Block, computers are used to calculate a 'safe zone', behind each moving train, which no other train may enter. The system depends on precise knowledge of where each train is and how fast it is moving. With Moving Block, lineside signals are unnecessary, and instructions are passed direct to the trains. It has the advantage of increasing track capacity by allowing trains to run much closer together.
[edit] Types of rail system
- Regional rail and rapid transit, the most common types of rail system, has reasonably high speeds and high axle loadings.
- Light rail systems are designed for lower speeds and loadings and often have simplified specifications.
- High-speed rail is a rail system designed to withstand high speed trains.
- Monorails are rarely used instead of light rail systems for commuter transport, etc.
- Maglev is a recent development with as yet only one real implementation.
- Rack railways are used to cross steep slopes on mountain railways.
- Industrial railway refers to specialized rail systems, such as those used inside factories or mines.
[edit] Permanent way and railroad construction
The permanent way trails through the physical geography. The tracks' geometry is limited by the physical geography.
[edit] Types of vehicle
Trains are pushed/pulled by one or more locomotive units. Two or more locomotives coupled in multiple traction are frequently used in freight trains. Railroad cars or rolling stock consist of passenger cars, freight cars, maintenance cars and in America cabooses. Modern passenger trains sometimes are pushed/pulled by a tail and head unit, of which not both need to be motorised or running. Some passenger trains, mostly commuter trains or trains on quiet rural lines and metros, consist of multiple units.
[edit] Passenger operations
Most public transport passenger operations happen in the train station and in the passenger car. The passenger buys a ticket, either in the station, or on the train (sometimes at a higher fare). There are two ways of validating a ticket. In one case the passenger validates the ticket himself (by perforating it, for instance) and this is randomly checked by a ticket controller. A conductor checks all persons on the train, validates the ticket and devaluates it, so it cannot be used again. Some passenger cars, especially in long distance high speed trains have a restaurant or bar. These need to be catered. In recent times, train catering has been diminished somewhat by vending machines in the train station or on the train.
[edit] Freight operations
Freight or cargo trains are loaded and unloaded in freight yards, by using cranes.
[edit] Locomotive operations
When inactive, locomotives are housed in a train depot. In engine facilities, or a Traction Maintenance Depot, locomotives are cleaned, repaired, etc. Decommissioned locomotives are sometimes used to heat passenger cars and defrost railroad switches in winter. After this period, locomotives (and other rail vehicles) are turned into scrap or are left to rust in a train depot. Some end up in railway museums or are bought by railway preservation groups.
Steam locomotives are housed in a circular train depot, a roundhouse that surrounds a turntable.
[edit] Train composition and operations
Trains are composed in a classification yard. These large, uninviting structures are excellent locations for train spotting and graffiti sighting. Switcher or shunter locomotives help the composing.
[edit] Background factors (feasibility)
Each transport system represents a contribution to a country's infrastructure, and as such must make economic sense or eventually close. From this, each will have a particular role or roles to perform. These may change with time but they will affect the specifications of each particular system.
[edit] Extrinsic factors
Rail transport systems are built into the landscape, including both the physical geography (hills, valleys, etc) and the human geography (location of settlements). The rail transport system may in turn feedback into the human geography.
[edit] Physical geography
The permanent way of a system must pass through the geography and geology of its region. This may be flat or mountainous, may include obstacles such as water and mountains. These will determine in part the intrinsic nature of the system. The slope at which trains run needs also be calculated correctly. In this stage, it is decided where tunnels will pass.
[edit] Human geography
Rail transport systems affect the human geography. Large cities (such as Nairobi) may be founded by a railroad passing through. Historically, when a station has been built outside the town or city it is intended to serve, that town has expanded to include the station, or buildings (especially Inns) sprung up near the station. The existence of a station may increase the number of commuters who live in a town or village and so cause it to become a dormitory town. The transcontinental railroad was a large factor in American colonization of the Western frontier. China's railroad expansion into Tibet may have similar consequences.
[edit] Historical factors
Rail transport systems are often used for purposes for which they were not designed, but have evolved into due to changes in the human geography. Politics can play a large part in decisions about railways, such as the Beeching Axe. In the UK, building or rebuilding a railway required an Act of Parliament.
