Editing Third rail (section)

== Description ==
Third-rail systems are a means of providing electric traction power to trains using an additional rail (called a "conductor rail") for the purpose. On most systems, the conductor rail is placed on the [[railroad tie|sleeper]] ends outside the running rails, but in some systems a central conductor rail is used. The conductor rail is supported on [[ceramic]] [[Insulator (electricity)|insulators]] (known as "pots"), at top contact or insulated [[Bracket (architecture)#Specialized brackets|brackets]], at bottom contact, typically at intervals of around {{Convert|10|ft|}}.{{what|i can't parse this sentence|date=March 2024}}

The trains have metal contact blocks called collector shoes (also known as [[contact shoe]]s or pickup shoes) which make contact with the conductor rail. The traction current is returned to the generating station through the running rails. In North America, the conductor rail is usually made of high conductivity [[steel]] or steel bolted to [[aluminium]] to increase the conductivity.  Elsewhere in the world, extruded aluminium conductors with stainless steel contact surface or cap, is the preferred technology due to its lower electrical resistance, longer life, and lighter weight.<ref>{{cite conference|last=Forman |first=Keith G.|date=16 April 2013|title=Aluminium/Stainless Steel Conductor Technology: A Case for its Adoption in the US|conference=2013 IEE/ASME Joint Rail Conference}}</ref> The running rails are electrically connected using wire bonds or other devices, to minimise resistance in the electric circuit. Contact shoes can be positioned below, above, or beside the third rail, depending on the type of third rail used: these third rails are referred to as bottom-contact, top-contact, or side-contact, respectively.

The conductor rails have to be interrupted at [[level crossing]]s, [[Crossover (rail)|crossovers]], and [[traction substation|substation]] gaps.  Tapered rails are provided at the ends of each section to allow a smooth engagement of the train's contact shoes.

The position of contact between the train and the rail varies: some of the earliest systems used top contact, but later developments use side or bottom contact, which enabled the conductor rail to be covered, protecting track workers from accidental contact and protecting the conductor rail from frost, ice, snow and leaf-fall.<ref name="rlhs">{{cite journal|last=Middleton|first=William D.|date=9 September 2002|title=Railroad Standardization – Notes on Third Rail Electrification|journal=Railway & Locomotive Historical Society Newsletter|volume=27|issue=4|pages=10–11}}</ref>
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=== Gallery ===
<gallery class="center" heights="160" widths="250" caption="Descriptions">
File:Thirdrailillustration.png|Third rail layout:<br>1:&nbsp;[[Plank (wood)#Coverboard|coverboard]] 2:&nbsp;[[Electricity|power]] [[Rail profile|rail]] 3:&nbsp;[[Insulator (electricity)|insulator]] 4:&nbsp;[[Railroad tie|sleeper]] 5:&nbsp;[[Rail profile|rail]]
File:Third Rail for Toronto Transit Commission.jpg|Third rail (top) at [[Bloor-Yonge station]] ([[Line 1 Yonge–University|Line 1]]) on the [[Toronto subway]]. Energized at 600 volts DC, the third rail provides electrical power to the [[Traction motor|power-train]], and [[Head-end power|ancillaries]] of the subway cars.
File:Metro Paris rubber wheel.jpg|[[Paris Métro]]. The [[Guide bar|guiding rails]] of the rubber-tyred lines also function as [[Electrical conductor|current conductors]]. The horizontal [[contact shoe]] is between the pair of rubber wheels.
File:Stansted Airport People Mover.JPG|London Stansted Airport people mover, showing rail switch
</gallery>