Editing Light rail (section)

==Infrastructure==
===Track gauge===
Historically, the [[track gauge]] has had considerable variations, with [[narrow gauge railways|narrow gauge]] common in many early systems. However, most light rail systems are now [[standard gauge]].<ref name="Bottoms" /> Older standard-gauge vehicles could not negotiate sharp turns as easily as narrow-gauge ones, but modern light rail systems achieve tighter turning radii by using [[articulated car]]s. An important advantage of the standard gauge is that standard railway maintenance equipment can be used on it, rather than custom-built machinery. Using standard gauges also allows light rail vehicles to be conveniently moved around using the same tracks as freight railways. Additionally, wider gauges (e.g. standard gauge) provide more floor clearance on [[low-floor tram]]s that have constricted pedestrian areas at the wheels, which is especially important for wheelchair access, as narrower gauges (e.g. metre gauge) can make it challenging or impossible to pass the tram's wheels. Furthermore, standard-gauge rolling stock can be switched between networks either temporarily or permanently, and both newly built and used standard-gauge rolling stock tends to be cheaper to buy, as more companies offer such vehicles.

===Power sources===
[[Overhead lines]] supply electricity to the vast majority of light rail systems.<ref name="APTA-def" /> This avoids the danger potentially presented by an electrified [[third rail]].<ref name=":3" /> The [[Docklands Light Railway]] uses an inverted third rail for its electrical power, which allows the electrified rail to be covered and the power drawn from the underside. Trams in [[Bordeaux tramway|Bordeaux]], France, use a [[Ground level power supply|special third-rail configuration]] where the power is only switched on beneath the trams, making it safe on city streets. Several systems in Europe and a few recently opened systems in North America use [[Diesel engine|diesel]]-powered trains.

===Ground-level power supply for trams===
{{Main|Ground-level power supply}}
When electric streetcars were introduced in the late 19th century, [[conduit current collection]] was one of the first ways of supplying power, but it proved to be much more expensive, complicated, and trouble-prone than [[overhead wires]]. When electric street railways became ubiquitous, conduit power was used in those cities that did not permit overhead wires. In Europe, it was used in London, Paris, Berlin, Marseille, Budapest, and Prague. In the United States, it was used in parts of New York City and Washington, D.C.<ref>{{Cite book|last=Post|first=Robert C.|title=Urban Mass Transit: The Life Story of a Technology|url=https://archive.org/details/urbanmasstransit00post|url-access=limited|publisher=[[Greenwood Press]]|year=2007|pages=[https://archive.org/details/urbanmasstransit00post/page/n61 45]–47|isbn=978-0-313-33916-5}}</ref> [[Third rail]] technology was investigated for use on the [[Gold Coast, Queensland|Gold Coast]] of Australia for the [[G:link]] light rail,<ref>{{cite web|url=http://www.pb.com.au/gclightrail |archive-url=https://web.archive.org/web/20030319223746/http://www.pb.com.au/gclightrail/ |url-status=dead |archive-date=19 March 2003 |title=Gold Coast Light Rail Feasibility Study |publisher=Commonwealth Government, Gold Coast City Council & Queensland Government Queensland Transport |date=23 December 2004 }}</ref> though power from [[overhead line]]s was ultimately utilized for that system.

In the French city of [[Bordeaux]], the [[Bordeaux tramway|tramway network]] is powered by a [[Ground-level power supply|third rail]] in the city center, where the tracks are not always segregated from pedestrians and cars.<ref>{{Cite press release|title=Bordeaux Light Rail Route Will Operate Without Overhead Lines |publisher=[[American Public Transportation Association]] |year=2003 |url=http://www.apta.com/services/intnatl/intfocus/bordeaux.cfm |access-date=21 December 2007 |url-status=dead |archive-url=https://web.archive.org/web/20081201155854/http://www.apta.com/services/intnatl/intfocus/bordeaux.cfm |archive-date=1 December 2008 }}</ref> The third rail (actually two closely spaced rails) is placed in the middle of the track and divided into eight-metre sections, each of which is powered only while it is completely covered by a tram. This minimizes the risk of a person or animal coming into contact with a live rail. In outer areas, the trams switch to conventional [[Overhead lines|overhead wires]]. The Bordeaux power system costs about three times as much as a conventional overhead wire system and took 24 months to achieve acceptable levels of reliability, requiring the replacement of all the main cables and power supplies.<ref>{{cite web|url=http://www.railway-technology.com/contractors/suburban/alstom/press17.html|access-date=26 December 2009|title=99% AVAILABILITY AND EXCEPTIONALLY HIGH PASSENGER LEVELS : THE BORDEAUX URBAN TRAMWAY IS A RESOUNDING SUCCESS|website=Railway-Technology.com|publisher=Net Resources International|archive-url = https://web.archive.org/web/20080613175705/http://www.railway-technology.com/contractors/suburban/alstom/press17.html |archive-date = 13 June 2008}}</ref> Operating and maintenance costs of the innovative power system still remain high. However, despite numerous service outages, the system was a success with the public, gaining up to 190,000 passengers per day.

===Automatic train operation===
{{Main|Automatic train operation}}
[[Automatic train operation]] is employed on light rail networks, tracking the position and speed of a train and hence adjusting its movement for safety and efficiency.<ref>{{Cite web |title=ATO: The Key to the Future of Rail? |url=https://criticalsoftware.com/multimedia/critical/en/q5rvGbO7c-CSW_-_Railway_-_White_Paper_-_Automatic_Train_Operation.pdf |access-date=24 July 2024 |publisher=[[Critical Software]] |quote=Serving as a fundamental component of metro and light rail networks, ATO utilises sensors and communication systems to monitor train positions and speeds, automatically adjusting train movements to ensure safe and efficient operations.}}</ref>