Dark territory is a term used in the North American

railroad Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

industry to describe a section of running

track Track or Tracks may refer to: Routes or imprints * Ancient trackway, any track or trail whose origin is lost in antiquity * Animal track, imprints left on surfaces that an animal walks across * Desire path, a line worn by people taking the shorte ...

not controlled by

signals In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

Train In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and Passenger train, transport people or Rail freight transport, freight. Trains are typically pul ...

movements in dark territory were previously handled by timetable and train order operation, but since the widespread adoption of two way radio communications these have been replaced by

track warrant A track warrant is a set of instructions issued to a train crew authorizing specific train movements. The system is widely used in North America. The warrant is issued by the train dispatcher and delivered to the train crew via radio. The train cr ...

s and

direct traffic control Direct traffic control (DTC) is a system for authorizing track occupancy used on some railroads instead of or in addition to signals. It is known as "direct" traffic control because the train dispatcher gives track authority directly to the train ...

, with

train dispatcher A train dispatcher (US), rail traffic controller (Canada), train controller (Australia), train service controller (Singapore) or signaller (UK), is employed by a railroad to direct and facilitate the movement of trains over an assigned territory, ...

s managing train movements directly. Today most dark territory consists of lightly used secondary branch lines and industrial tracks with speeds ranging between and ; however, there do exist a small minority of main lines that fall into the category. In the UK and

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

the term applies to rail track where the

signalling system In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

does not pass the signal indications nor track occupancy back to a

signal box In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

. As such the position of trains is not visible to signallers, and so the track is "dark".

Safety concerns

The primary safety concerns with dark territory stems from the lack of any form of direct or indirect train detection along the route. Train detection systems such as

track circuits A track circuit is an electrical device used to prove the absence of a train on rail tracks to signallers and control relevant signals. An alternative to track circuits are axle counters. Principles and operation The basic principle behind t ...

not only alert other trains to the presence of a potential hazard, but can also alert dispatchers or other monitoring systems to the same. Dark territory also lacks the ability to control or lock

switches In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

onto the main track, detect misaligned switches, broken rails or runaway rail cars. In most cases these drawbacks are mitigated by the light traffic and low speed of the trains in dark territory, but a

runaway train A runaway train is a type of railroad incident in which unattended rolling stock is accidentally allowed to roll onto the main line, a moving train loses enough braking power to be unable to stop in safety, or a train operates at unsafe speeds d ...

(such as the

crude oil Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...

unit train in 2013's Lac-Mégantic derailment) will not respect limits on speed and is not detectable by

rail traffic controller A train dispatcher (US), rail traffic controller (Canada), train controller (Australia), train service controller (Singapore) or signaller (UK), is employed by a railroad to direct and facilitate the movement of trains over an assigned territory, ...

s on a line with no signals or track circuits. The total reliance on manual procedures to ensure safety has occasionally resulted in

train wreck A train wreck, train collision, train accident or train crash is a type of disaster involving one or more trains. Train wrecks often occur as a result of miscommunication, as when a moving train meets another train on the same track; or an acci ...

s, some with fatalities, due to either miscommunication or oversight on the part of operating personnel. In 1948 the

Interstate Commerce Commission The Interstate Commerce Commission (ICC) was a regulatory agency in the United States created by the Interstate Commerce Act of 1887. The agency's original purpose was to regulate railroads (and later trucking) to ensure fair rates, to eliminat ...

set a nationwide speed limit of for trains not protected by some kind of block system (including manual block and track warrants) and in 2012 this was expanded to include all lines considered dark territory. Since 1991 the

National Transportation Safety Board The National Transportation Safety Board (NTSB) is an independent U.S. government investigative agency responsible for civil transportation accident investigation. In this role, the NTSB investigates and reports on aviation accidents and incid ...

(NTSB) had recommended that railroads be required to install new forms of signaling technology, such as

positive train control Positive train control (PTC) is a family of automatic train protection systems deployed in the United States. Most of the United States' national rail network mileage has a form of PTC. These systems are generally designed to check that trains a ...

(PTC), that can stop trains from exceeding their procedural authorities and warn them of improperly lined switches. The

Rail Safety Improvement Act of 2008 The Rail Safety Improvement Act of 2008 is a United States federal law, enacted by Congress to improve railroad safety. Among its provisions, the most notable was the mandate requiring positive train control (PTC) technology to be installed on ...

and subsequent amendments requiring installation of PTC technology on parts of the U.S. rail network by December 31, 2018, may eliminate many sections of currently dark territory.

Safety concerns

See also

References

Further reading