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2 FINDINGS
Pages 13-28

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From page 13... ... Appendix 9-H recognizes that individual phase times are variable under traffic-actuated control and suggests that the average cycle length and phase times may be approximated by assuming that the controller is effective in its objective of keeping the critical approaches nearly saturated. Mathematically, this relationship may be stated as: CaV L/( ~ Y/XT) Read the entire page →
From page 14... ... Green Time Determination for Traff-lc-Actuated Controllers The detenn~nation of required Been time is a relatively straightforward process when the cycle length is given; however, traffic-actuated controllers do not recognize specified cycle lengths. Instead, they determine, by a mechanical analogy, the required green time given the length of the previous red interval and the arrival rate. Read the entire page →
From page 15... ... 8 :D ~6 ._ an _ a) ._ ~4 > o Proposed Analytical Model Green time based on phase extension time l As HCM Appendix II Green time based on target v/c ratio _ / Red Time At\ Time (seconds) Read the entire page →
From page 16... ... Minimum Phase Times The whole question of minimum phase time requires more attention. The specified minimum green time constraints are valid only for pretimed phases and phases that are set to recall to the minimum time regardless of demand. Read the entire page →
From page 17... ... In this figure, the x axis represents the approach volume, y axis shows free queue values, and the vertical axis is the estimated phase times by the proposed method. The effect of the Bee queue value may be easily observed from this three dimensional surface plot. Read the entire page →
From page 18... ... satisfactorily, either by simulation, or in the field, it is suggested that the analysis is robust and the HCM Chapter 9 procedure wall be enhanced if the free queue is included. EVALUATION OF THE SIGNAL TIMING ESTIMATION MODEL Phase Time Comparison between NETSIM and the Proposed AnalYtical Model The proposed signal timing estimation mode} was evaluated using simulation data Tom nine intersections and field data Tom one intersection. Read the entire page →
From page 19... ... , the regression line is close to I: ~ slope. The dispersion of the data poirts is small, indicating that the phase time estimates from the analytical model are close to the field data. Read the entire page →
From page 20... ... Phase time comparison between the proposed analytical mode! and field data ESTIMATION OF DELAY AT TRA~IC-ACTUATED INTERSECTIONS The traditional delay formulation used by virtually all analytical models is based on two terms which are added together to produce the total delay (D) Read the entire page →
From page 21... ... to determine the phase times, the value ofthe uniform delay, Du (i.e., the area contained within the QAP) , may be computed by a simple extension to the existing phase time prediction model. Read the entire page →
From page 22... ... The computation of the incremental delay term also adopts the delay model proposed by Ak~elik and Chung [61. The incremental delay, D2, can be computed by the following formula: NCHRP Project 3-48 Final Report: Page 22 Read the entire page →
From page 23... ... Note that the delay model proposed by Akcelik and Chung was derived by calibration of the general model using simulation data. NCHRP Project 3-48 Final Report: Page 23 Read the entire page →
From page 24... ... \| 0.084 \| 0.1 19 \| 0.125 \| 0.23 1 \| Comparison of Delav Estimates between Delav Models and NETSIM Simulation For traff~c-actuated operation, the accuracy of the delay model depends on the accuracy of the estimated signal timing plan. The different analytical models were incorporated as options into the computational structure described in Appendix E Read the entire page →
From page 25... ... Figure 6 shows the NET SIM delay estimates plotted against the corresponding estimates from the HCM delay mode! based on the phase times predicted by the Appendix IT technique. Read the entire page →
From page 26... ... Delay comparison between the lICM Delay Model and NETSIM Model ~ Delay Estimates Based on Timing Estimated by the Proposed Analytical Mode! Figure ~ plots the NETSIM total delay estimates against the corresponding estimates Dom Delay Mode} ~ associated with the phase times predicted by the proposed analytical model. Read the entire page →
From page 27... ... Figure 9 plots the NET SIM total delay estimates against the corresponding estimates Dom Delay Model II associated with the phase times predicted by the proposed analytical model. A small dispersion of the data points is shown in this figure, as confirmed by a high R square value of 0.90. Read the entire page →
From page 28... ... This rationale favors Delay Mode} IT. NCHRP Project 3-48 Final Report: Page 28 Read the entire page →

From page 13...

... Appendix 9-H recognizes that individual phase times are variable under traffic-actuated control and suggests that the average cycle length and phase times may be approximated by assuming that the controller is effective in its objective of keeping the critical approaches nearly saturated. Mathematically, this relationship may be stated as: CaV L/( ~ Y/XT)

2 FINDINGS Pages 13-28

2 FINDINGS
Pages 13-28