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QAP diagrams for leading Protected-Permitted

Matthew Muresan
QAP diagrams for leading Protected-Permitted was posted on September 1st, 2022 at 5:56 PM UTC
regarding Chapter 31: Signalized Intersections: Supplemental

I have a question about QAP construction in protected-permitted cases.

In the HCM "r" is defined as the effective red time, which is the Cycle time (C) - the effective green times (g). For a protected-permitted signal, as I understand this would be C - gp - gl.

I am looking Exhibit 31-15 in the HCM 6th edition, a sample QAP for protected-permissive is shown. In this diagram "r" is used to calculate the queue accumulation in the red period that follows the permissive period (gp).

My question is why isn't this period defined as (r - l1,p) and l1,p included in Qq for QAPs for leading protected-permitted. The loss time in gp occurs before the start of gp (between gp and gl), but is included in r that is used to calculate queue accumulation after only the permitted period.

For greater clarity as to what I am asking, I have uploaded a picture of the diagram in the HCM with the way I understand the QAP should be constructed for this case to Google Drive here.


I realise this should actually be in the "questions and clarification" section, not sure if ths can be moved there.

(Edited September 1st, 2022 at 6:20 PM UTC)
Shen Dong
University of Florida
RE: QAP diagrams for leading Protected-Permitted was posted on October 19th, 2022 at 9:06 PM UTC

Hello Matthew,

After reviewing Page 31-3 and Exhibit 31-1, I realize that the effective red time r includes start-up lost time (l1), and the effective green time g doesn’t include l1. In other word, r= red interval + l1. And g= Dp-l1-l2 for exhibit 31-1. As indicated in the last paragraph of Page 31-3, “the queue reaches its maximum size l1 seconds after the green interval starts.” Please let me know if you have any other questions.

Thank you, Shen

(Edited October 19th, 2022 at 9:36 PM UTC)

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