Specifications
ST900 Family General Handbook
667/HB/32900/000 Issue 10 Page 99 of 265
The far side pedestrian lamp sequence includes an extendable blackout period that
extends the inter-green time between the pedestrian phase and any conflicting
vehicle phases.
The complete inter-green consists of:
a fixed minimum blackout clearance time (PBT),
an extendable period (CMX) plus its switched clearance period (CDY),
a fixed red clearance period (CRD)
a fixed two second vehicle red/amber time
The fixed part of the inter-green from a far side pedestrian phase to a vehicle phase
is controlled by larger of either:
The configured inter-green time (IGN)
OR
The fixed blackout and red clearance times (PBT+CRD) plus the red/amber time
The controller will use the configured inter-green time unless that would allow the
vehicle red/amber time to start before the clearance red period has finished, i.e.
when IGN is set lower than PBT plus CRD plus two seconds. If a customer does not
specify an inter-green time, a value of 5 seconds will be used.
Consider the example below.
IGN:9
2
R/A
CMX+CDYPBT
PED:
VEH1:
IGN:5
ign
GREEN
RED GREEN
RED
R/A
VEH2: RED GREEN
CRD
BLACKOUT
ign
The configured inter-green time (IGN:5) for PED to VEH1 is set below the required
minimum clearance time (PBT:4) plus the required red clearance period (CRD:2)
plus the red/amber time (2 seconds). Therefore the actual inter-green (shown as
‘ign’) would run longer than the configured inter-green value and would actually run
for eight seconds governed by the PBT, CRD and red/amber times. This would be
the normal case on a stand-alone pedestrian stream where the IGN time is zero.
However, if the configured inter-green time to one vehicle phase is increased to say
nine seconds (VEH2), it controls the actual inter-green time and thus delays the
vehicle phase by an extra one-second. Note that the vehicle is always delayed by
one second, regardless of how long the extendable period actually runs for, and so
always appears one second later than the other vehicle phase.