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Add notes on types of rail and sleepers used
'''Viaduct''': A viaduct is a particular type of bridge characterised by having a number of small spans, for crossing a valley or a gorge.
==Track, rails and sleepers==
[[File:Rail profile.svg |thumb|300px|right| Rail profiles (Wikipedia)]]
The majority of the SVR’s 16 miles of track uses bullhead rail. This type of rail was the standard on British railways between the mid-19th and mid-20th centuries. The rail sits in chairs which are in turn attached to the sleepers, and the rail is held fast to the chairs using metal wedges or keys.
After the mid-20th century, Britain’s railway network moved over to using flat-bottom rail. This sits directly on the sleepers without the need for chairs, and is held by to the sleepers using Pandrol clips. Some flat-bottom rail can be seen on the SVR, including the section near [[Country Park Halt]].
Individual rails of both types are typically 60 ft in length, and are joined to each other by fishplates. The fishplates allow a certain amount of longitudinal movement to cater for expansion and contraction of the rails with temperature changes. Each section of the line is regularly inspected to check for faults in the fishplates and rail fastenings.
Modern railway practice is to use continuously welded rail (CWR), in which adjacent lengths of rail are welded together, removing the need for fishplates. This gives a smoother ride and reduces maintenance costs. Heritage railways do not generally use CWR, although the section of track through [[Bewdley Tunnel]] was re-laid with CWR during the winter of 2011-12 in order to simplify future maintenance.
The 1960s track acquired by the SVR from BR predominantly used wooden sleepers, many of which were in less than ideal condition. Although wooden sleepers have generally been retained in stations for aesthetic purposes, the rest of the line has been re-laid over the years using more modern concrete sleepers.
<gallery>
File:Bullhead_Rail_20150528.jpg |A fishplate joining two lengths of bullhead rail
File: Flat-bottom_rail_20150528.jpg | Flat-bottom rail near Country Park Halt
File:Les sabots rouges (Pandrol clips) - geograph.org.uk - 667729.jpg | Pandrol clips (Wikimedia Commons)
</gallery>
