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{{main|Safeworking (railway)}}

{{main|Safeworking (railway)}}

In order to prevent trains from colliding, railroads use electrical signaling systems.  The most common systems in use today are based on variations of [[automatic block signaling]], which can be supplemented by [[positive train control]].

In order to prevent trains from colliding, railroads use electrical signaling systems.  The most common systems in use in the united states are based on variations of [[automatic block signaling]], which can be supplemented by [[positive train control]].

==== Automatic block signaling ====

==== Automatic block signaling ====

[[Positive train control]] is a technology by which "automatic control systems" are able "to override mistakes made by human operators" in order to prevent train collisions.<ref name="NTSB recommendation">http://www.ntsb.gov/recs/mostwanted/positive_train.htm</ref>  [[Amtrak]]'s Northeast Corridor, for example, uses a system that comprises two elements, "positive train stop" and "civil speed enforcement," which together provide the functionality of positive train control.<ref name="NTSB recommendation" />

[[Positive train control]] is a technology by which "automatic control systems" are able "to override mistakes made by human operators" in order to prevent train collisions.<ref name="NTSB recommendation">http://www.ntsb.gov/recs/mostwanted/positive_train.htm</ref>  [[Amtrak]]'s Northeast Corridor, for example, uses a system that comprises two elements, "positive train stop" and "civil speed enforcement," which together provide the functionality of positive train control.<ref name="NTSB recommendation" />

Positive train control systems can prevent those collisions that are caused by crewmember inattention to signal indications.<ref name="NTSB testimony">''See'' [http://www.ntsb.gov/speeches/s050428.htm National Transportation Safety Board:  statement on positive train control].</ref>

Positive train control systems can prevent those collisions that are caused by crew member inattention to signal indications.<ref name="NTSB testimony">''See'' [http://www.ntsb.gov/speeches/s050428.htm National Transportation Safety Board:  statement on positive train control].</ref>

== Trains ==

== Trains ==