wunder beta🚦 How does a traffic light system decide timing
Phases, detectors, and green waves — how signal timing shares the intersection.
What you’ll learn
- Signals Are a Shared ScheduleDefine phases, cycles, and green splits as the basic timing vocabulary.Traffic signals time-share the intersection; cycle length and splits allocate scarce green among competing movements.
- Fixed Timing Versus Sensing TrafficContrast pretimed and actuated control and explain clearance intervals.Clocks can run fixed plans; detectors allow demand-responsive greens; yellow and all-red protect transitions.
- Coordination and Smarter NetworksExplain offsets, adaptive control, and multimodal timing goals.Neighboring signals coordinate for progression; adaptive systems update plans with data; pedestrians and transit reshape objectives.
Questions this course answers
What is a signal cycle?
A cycle is the full loop through the phase sequence; its length is measured in seconds.
Match each idea to its role
Pretimed ignores live emptiness; detectors feed actuation; clearance intervals protect phase changes.
Order these steps for coordinating an arterial
Measurement informs timing parameters; offsets create progression; field observation validates the green wave.
If a simplified cycle is 100 seconds and the main street receives 45% of the cycle as green (ignoring yellow), about how many seconds of main-street green is that?
0.45 × 100 seconds = 45 seconds of green in this toy example.
Grounded in trusted sources
- U.S. Federal Highway Administration — Traffic Signal Timing Manual concepts
- Institute of Transportation Engineers — signal timing resources
- Highway Capacity Manual / TRB — intersection operations concepts
- Local DOT public explainers on actuated signals and coordination
Every Wunder lesson is built from real, reputable sources — never invented.
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