Sunday, November 01, 2009
Signal at Ustick and Mitchell, bike lanes and trash carts, signal at Overland and Silverstone
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| | Dear Road Wizard: Can you please explain the signal at Ustick and Mitchell streets? Which street has higher priority? J.H.@ |
| | On October 4, 2009, I described the "fully actuated" signal at Ten Mile and McMillan roads. Ustick/Mitchell is another fully-actuated signal.
Ustick traffic volumes are higher than Mitchell's. The signal rests in green for Ustick traffic. In this sense, Ustick has "priority" over Mitchell.
Scenario One: Sensors in Ustick have "seen" no traffic on Ustick for two seconds AND someone shows up on Mitchell. The controller quick-quick gives Ustick yellow, then all-red, a total of five seconds. Mitchell gets green. Mitchell may seem to have "priority" because five seconds is a very short wait.
Scenario Two: Thru and left-turn traffic is heavy-heavy on both streets. The controller goes to built-in maximums and a take-turns routine. Left turn moves for each street get 20 seconds (15 green + 4 yellow + 1 all red). Ustick's maximum thru green is 65 seconds (60G + 4Y + 1AR) before it surrenders to Mitchell. Mitchell's maximum thru green is only 45 seconds (40G + 4Y + 1AR). In this circumstance, Ustick has "priority" with more thru green time.
Scenario Three: Once you get the hang of this, prepare for ACHD to change things! In the works is a synchronization program for Ustick between Cole and Five Mile roads, at least for the evening peak hour. Estimated time of launch: January 2010.
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