UTC System Handbook - Siemens

System Handbook for an STC UTC System 666/HE/16940/000
(6) An optional plan description field may be completed with a textual
description of any changes made.
7.5.5 Temporary Amendments
The System provides a facility for varying an implemented plan 17 . This allows the
stage durations, offsets and cycle time to be modified. Once the plan has been
changed it is treated by the System as an operator imposed fixed time plan; this
means that the next timetable action to select SCOOT or another fixed time plan
will fail causing an operational alarm.
7.6 Green Waves
7.6.1 Introduction
The green wave facility is intended to control a number of junctions and/or
pelicans so that a vehicle travelling on a predetermined route may pass through
the junction or crossing with minimum delay. Typically it is used to provide a
quick means for fire engines to get from their base through the city to the area of a
fire. It could also be used to provide a smooth path for an ambulance carrying a
critically ill patient, or for VIPs. Equipment for a particular green wave can be
associated with any number of TCCs.
Individual controllers are only affected just before and whilst the vehicle passes
through. The green wave can be operated for controllers under fixed time or
SCOOT control. If Controller Checks is active the checks are abandoned in favour
of the green wave, see section 7.14.
The System allows a route to be called again before the first call has been
completed. This has the effect of initiating another wave down the route.
If more than one route attempts to use the same controller at the same time then
the first request is honoured and no warning given that the second, or third, wave
has not been honoured.
7.6.2 Defining the route
In order to access the route an SCN must be created for it. Once this is done a
special "plan" is created. The plan defines both the controllers affected by the
green wave and what they are expected to do during one. This is defined in terms
of the duration of time a specified stage is held and when it should start, timed
from the beginning of the wave.
The duration is typically set to 60 seconds. This gives time for the current stage to
complete its minimum, the intergreen and a clearance period to have occurred
before the vehicle arrives and a 30-second leaving window to the vehicle.
It is a normal requirement of each controller on the route that the stage to be used
for the green wave must be accessible from all configured controller stages. If this
is not true then the controller moves through the stages in a cyclic order until the
17 The temporary data created using these commands is stored in plan 47. Consequently no data
can be entered for plan 47 nor can it be prepared.
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