Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 10 Page 103 of 265
vehicle period mode (see section 23.3) and for a ‘linked’ changed, UTC, local link or
CLF.
However, if the speed discrimination or speed assessment facility is enabled on the
stream (because of the higher speed of the traffic), the all-red time runs for at least 3
seconds in order to meet UK requirements. Also see section 9.4.2.
6.11.5 Fixed Clearance Period
Even though the Pedestrian lamp sequences default to including the extendable
blackout period, if the clearance maximum (CMX) time is set down to zero, the
phase will run a fixed blackout period determined solely by PBT and a fixed
minimum all-red period determined solely by CRD.
Note that for non UK, the blackout period can be configured to show flashing green
for example.
MIN
Amber
PAR PBT3 2CRD
Blackout
Red
Green
Red R/A
Green
Green
RedPed:
Veh:
Figure 20 – Fixed Pedestrian Clearance Period
The controller checks that the IGN inter-green time is not shorter than the required
clearance period. After the pedestrian phase, the controller will ensure that if
PBT+CRD are set longer than IGN, the vehicle red/amber period does not start until
the pedestrian blackout period (PBT) and the minimum red clearance period (CRD)
have finished.
On a stand-alone stream, the above is true even if the red clearance time CRD is
set to zero, i.e. the vehicle red/amber time will start when the blackout time PBT
expires.
However, on an intersection stream, if the red clearance time CRD is set to zero (as
well as CMX), the controller reverts to its original style of operation to be backward
compatible. If CRD is zero, the inter-green between the pedestrian phase and the
vehicle phase is controlled solely by the IGN handset command, even if the blackout
time PBT is set longer. This ensures that existing configurations, which will default
to having CMX and CRD times set to zero, operate exactly as before.
6.11.6 Parallel Pedestrians
In the case where the pedestrian phase is running in parallel with a vehicle phase,
the pedestrian could be configured to terminate on a minimum green using special
conditioning. If the parallel vehicle phase was still being extended after the
pedestrian terminated, the pedestrian clearance periods could be completed by the