Term
| What are the disadvantages of fixed timing? |
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Definition
-Does not have the ability to react to demand fluctuations in real-time
-Demand values assumed
-Requires manual monitoring and updating
-Imposes unnecessary delay during very low-flow |
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Term
| What is the advantage of actuated signals? and what is required to use them? |
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Definition
-Signal timing adapts to demand
-Requires vehicle detection and specific 'local' control |
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Term
| What is the purpose of the Local controller in actuated signals? |
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Definition
-Collects data from detectors
-Programmed to respond |
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Term
| How does an actuated signal adapt? |
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Definition
-changing phase structure
-changing green interval for a phase
-changing cycle length to incorporate changes in intervals |
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Term
| What is a partially and fully actuated signal? |
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Definition
Partially actuated signal only has the detector on minor road, which defaults green on major road.
-Fully actuated has detectors on all approaches |
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Term
| What happens when the flow becomes to high? |
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Definition
| the actuated signal then acts as a fix timing signal |
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Term
| What is the unit extension interval? |
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Definition
-time added to green when vehicle is detected-
-must be long enough for the vehicle to travel from the detector to the stop line |
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Term
| What is the purpose of minimum green (Gmin)? |
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Definition
-Avoid sudden phase switching
-allow clearing of vehicles queued |
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Term
| What is the purpose of Gmax? |
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Definition
| -to avoid the locking into green on one phase |
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Term
| What are the 6 steps in designed an actuated controller? |
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Definition
1)Establish phasing design
2)determine u for each phase
3)determine Gmin for each phase
4)Determine intergreen times and resulting amber and all red times
5)Determine Gmax for each phase and check cycle length
6)check pedestrian times |
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