Slow zone
Dual PSR on the 125 mph Midland Main Line at Belper
Temporary speed limit before a flange lubricator at Belper
A slow zone, in America, is an area where a train is forced to slow down for either structural, construction, power, signal, or track problems. Slow zones limit a train to about 10-35 MPH. Notification to train crews is referred to as a "slow order."
United Kingdom
In the United Kingdom the term "speed restriction" is used, either permanent (PSR), temporary (TSR) or emergency (ESR).
TSR and ESR
TSRs and ESRs are used where movement of the track is causing problems.
PSR
PSRs are usually only for curves or switches and crossings. PSRs may also be imposed where signal spacing is short relative to braking distances.
Dual PSR
As will be seen from the image, some PSRs are dual, allowing certain trains to pass at a higher speed, such as InterCity 125 (HST) and certain other classes.
See also
References
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