Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 175 of 265
the offset time internally; in this case calculating that an offset of just ‘1’ second is
actually needed (the difference between the offset and cycle times).
21.6.3 Using Different Start Times (Non Base Time CLF Only)
This system defines the offset between the controllers by altering the time at which
the plan starts. If this system is used, all the plans at each controller can request the
main road to appear at green at time 0 within the cycle time for example.
Note that this alternative is only available with the Non Base Time CLF system,
since in the Base Time CLF system, all plans are synchronised to a ‘base time’ so
the time that the plan is introduced does not synchronise the plan.
Figure 31 illustrates the offsets for the introduction of Plan 0 (morning peak), which
is introduced at ‘C’ at 08:30:00, at ‘B’ at 08:30:20 seconds, and at ‘A’ at 08:30:35
seconds.
Similarly, during the evening peak (Figure 32), Plan 1 is introduced at ‘A’ at
16:40:00, at ‘B’ at 16:40:19, and at ‘C’ at 16:40:46.
21.6.4 Using Different Group Times (Either CLF System)
This system defines the offset between the controllers by modifying the group times,
i.e. the start times of each group influence. It can be used with the Base Time CLF
system or the Non Base Time CLF system. However, with the Non Base Time CLF
system, the CLF plans should all be configured to start at exactly the same time, e.g.
8:30:00 or 16:10:00.
The plans at each intersection all reach time ‘0’ within the cycle time at the same
time, and the cycles at each intersection remain synchronised until the plan is
requested to finish.
Normally the group times would be configured as follows:
Plan 0 A B C Plan 1 A B C
Group 0
(Main Road)
0 0 0
Group 0
(Main Road)
0 0 0
Group 1
(Side Road)
40 45 35
Group 1
(Side Road)
30 25 25
Cycle Time 60 60 60 Cycle Time 45 45 45
However, to provide the required offsets between the controllers, the group times
should be modified as follows: