Part I: A Signal Timing Problem with Traffic Signal Systems

Part I: A Signal Timing Problem with Traffic Signal Systems

Here, George (Xiaozhao) Lu would like to introduce an innovative traffic signal system model he independently thought of, designed and implemented in VISSIM environment, with an aim to Contribute to solving a traffic problem regarding one major sustainable travel mode — walking.

The Highway Capacity Manual regulates that the parallel vehicle green interval must equal or exceed the “WALK” (equivalently ‘Green’) plus the “Flashing DONT WALK (FDW)” (equivalently ‘Yellow’). The length of “FDW” is calculated by a constant design walking speed and a specific crossing distance usually in terms of street width. So, the design speed is critical in determining how much clearance time is actually given to pedestrians.

Historical studies found the walking speed in a range of 1.0 to 8.0 feet/sec for varied populations. So, it is precarious to provide a uniform “FDW” length for a cane user and a young runner. Yet this is how an existing traffic signal system operates: the Manual on Uniform Traffic Control Devices designates 3.5 feet/sec for “FDW” timing. “What is the most appropriate design walking speed?” has kindled a nationwide debate, and a countermeasure is practiced via lowering design speed to lengthen the “FDW”.

However, let’s see what will happen if we invite a small design speed (1 foot/sec) to time the “FDW” in a NEMA signal system, with the intention of fully protecting a pedestrian population which has a foregoing range of walking speed change.

When the lengthened “FDW” exceeds the parallel green which is factually required for efficient vehicle movements, the additional green time resultant from this prolongation is operationally surplus. The longer vehicular right-of-way has to preempt an additional amount of green time from the next phase and consequently induce more red time which will inflict the whole intersection with increased queuing vehicular delays. Especially, as you observe later in video, this problem deteriorates enormously once those expeditious pedestrians vacate crosswalks: the residual “FDW” time is purely idle and the parallel vehicular green is underused; simultaneously, the long queuing vehicles halted by red are thirstily keen to enjoy their right-of-way.

An intelligent solution should be created for this sustainable mode being advocated, fostered, and nurtured worldwide for human well-beings.

We have limited fossil fuel on the only habitat, earth, in endless cosmos.
We have babies in cradles generation after generation.

Why not walk more??

Contact info (it’s True interest to know more from you in the era 🙂 ):
lu_xiaozhao@yahoo.com

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