Uni-Directional (U/D) Facility - Siemens ST950 Handbook

32.4

Uni-Directional (U/D) Facility

If only vehicles travelling in one direction over a detector are required to activate it,
whereas vehicles travelling in the opposite direction are not, the controller includes the
Uni-Directional (U/D) facility.
The facility uses two inputs that are connected to two inductive loops that partially
overlap on the carriageway, such that vehicles travelling in the required direction
activate the 'A' loop first, then the 'U' loop.
If the 'A' loop is activated first, the controller processes the 'A' input as normal.
However, if the 'U' loop is activated first, the 'A' input will be forced to remain inactive
(subject to a configurable time-out period), even if the 'A' loop input to the controller is
actually activated. This condition remains until both inputs return inactive when the
vehicle has passed.
Security classification
Version
Last Editor
Document Name
Copyright © Siemens plc 2015. All Rights Reserved.
Unrestricted
4
Paul Cox
ST950 General Handbook
Mobility Division, Traffic Solutions
Sopers Lane, Poole, Dorset, BH17 7ER
Page 90 of 107
Status Issued
Date 16-Jul-2015
Document No. 667/HB/46000/000
Mobility is a division of Siemens Plc