Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 247 of 265
In the following diagram, phases A and B are losing right of way and conflict with
phase D that is gaining right of way. Phase C is also losing right of way and conflicts
with phase E. The requirement is that phases D and E appear at green at the same
time on this stage to stage movement.
Example 1 shows the normal operation where a 10-second phase delay delays the
appearance of phase E.
Example 2 shows what happens when phase A has one missing red lamp. It delays
the appearance of phase D by 5 seconds. If a red lamp monitor time from A to E of 5
seconds is also specified, even though phases A and E do not conflict, phases D
and E still appear at green at the same time.
Example 3 shows what happens when phase B has missing red lamps and not
phase A. Phase D would be delayed since the inter-green time plus RLM delay from
B to D is 11 seconds. Given that there is already a 10-second phase delay on E, a
red lamp monitor time from B to E of 1 second would also give 11 seconds.
Phase D
Phase C
Phase E
Example 1
Example 2
Phase B
Phase A
10 Second Phase Delay
Phase D
Phase E
10 Second Phase Delay
Phase D
Phase E
Example 3
10 Second Phase Delay 1s
IGN A D:10
IGN B D:7
IGN C E:5 RLT C E:4
RLT A D:5
RLT A E:5
RLT B D:4
IGN A D:10
IGN A D:10
IGN B D:7
RLM times for this example are: A B C D E
A - - 5 5
Required delays when B - - 4 1
this phase terminates C - - - 4
with missing reds D - - - -
E - - - -
Figure 42 – First Red Lamp Failure Delays (Example 2)