Concept explainers
Effectof cycle length when saturation flow rates at
Answer to Problem 17P
Explanation of Solution
Given information:
Repeat
Shows a detailed layout of the phasing system and the intersection geometry used.
Calculation:
Equivalent hourly flow for north approach at left turn is given by,
Equivalent hourly flow
Peak hour volume
Peak hour factor
Substitute the values in equation
Calculate for other approaches like left turn, right turn and through movement in
Approach | North | South | East | East |
Left turn | ||||
Through movement | ||||
Right turn |
Calculate the critical volume for other approaches like left turn, right turn and through movement in
Left to north approach is left turn is
Through movement is
Approach | North | South | East | East |
Left turn | ||||
Through movement |
For the saturation flow rates at
Similarly calculate the saturation flow rates for other approaches in
Approach | saturation flow rates,
|
Through lanes | |
Through right lanes | |
Left lanes | |
Left through lanes | |
Left through right lanes |
Maximum value of the ratios of approach flow using formula,
Maximum value of ratios of approach flow to saturation flow to all lanes
Flow on lane groups
Saturation flow on lane group
Substitute the values in equation
Calculate for other
Approach | Phase | Phase | Phase | Phase |
Sum of critical ratio is given by,
Total lost time is given by,
Total lost time
Number of phases
Lost time for phase
Total all red time
Substitute the values in equation
Cycle length is given by,
Total effective green time is given by,
Allocated green time for phase
Allocated green time for other phases is given in the table
Phase | Allocated green time in sec |
Minimum green time for phase
Crosswalk length
Average speed of pedestrians
Number of pedestrians crossing during an interval
Substitute the values in equation
Minimum Green time for other phases is given Table
Phase | Minimum green time in sec |
From the Table
Sum of green and yellow time is given by,
Total cycle length is given by,
Conclusion:
Therefore by increasingsaturation flow rates at
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Chapter 8 Solutions
Traffic And Highway Engineering
- 1.. Please show work and steps. If an approach has a PHF of 0.90 and a counted hourly volume of 800 veh/hr what is the maximum 15-minute volume and peak rate of flow? What is the highest and lowest possible value of PHF? At a given location, the space mean speed is measured as 70 mph and the rate of flow as 2200 pc/h/ln. What is the density at this location for the analysis period? How could you decrease the density by 10%?arrow_forwardHelp For two circulating lane, Conflicting flow rate of 675 pc/hr . find total entry lane capacity.arrow_forwardFor two circulating lane, Conflicting flow rate of 675 pc/hr . find total entry lane capacity.arrow_forward
- QUESTION 2 The service flow rate is the maximum flow rate for a designated level of service. O True O Falsearrow_forwardThe minimum cycle length for an intersection is determined to be 95 seconds. The cirtical lane group flow ratios were calculated as 0.235, 0.250, 0.170 and 0.125 for phases 1- 4 respectively. What Xc was used in the determination of this cycle length, assuming a lost time of 5 seconds per phase?arrow_forwardThe normal flows on two approach roads at an intersection are respectively 500 pcu/h and 300 pcu/h. The corresponding saturation flow is 1600 pcu/h on each road. The total lost time per single cycle is 16 s. The optimum cycle time by Webster's method is A) 72.5 s B 58.0 s c) 48.0 s D) 19.3 sarrow_forward
- QUESTION 12 60 10. 15-min Volumes 75 40 Lane Configurations Y Consider the left turn movement from main street. If the conflicting flow rate is 280 veh/hr, and the critical headway, adjusted for heavy vehicles and grade, is 4.2 seconds, and the follow-up time, adjusted for grade, is 2.29 seco nds, calculate the potential capacity, Cp,4 (veh/h). Provide your answer to the nearest integer. SRCParrow_forwardCompute the peak hour factor if the hourly volume of traffic is 1800 vehicles/hour and the highest 15-min. volume is 750. (A) 0.5 B) 0.6 c) 0.4 D) 0.3arrow_forwardPlzz help For one circulating lane, Conflicting flow rate of 675 pc/hr . find total entry lane capacity.arrow_forward
- QUESTION 13 60 10 15-min Volumes Y 75 40 Lane Configurations SUCP What is the movement capacity of the left turn from the main street if the potential capacity is 1,238 veh/h?arrow_forwardQUESTION 10 During one hour, 1800 pedestrians passed by the observation point on the pedestrian walkway. The flow appeared to be relatively consistent over the hour (i.e. PHF-0.90). The effective walkway width was 5 ft. Pedestrian were moving at roughly 4.25 ft/sec. What was the observed average spacing (ft2/ped)? Record your answer to the nearest integer.arrow_forwardThe average normal flow on cross roads A and B during design period are 400 and 250 pcu per hour. The saturations flow values on these roads are estimated as 1200 and 1000 pcu per hour respectively. The all-red time required for pedestrian crossing is 12secs. Calculate cycle time for two phase signal system.arrow_forward
- Traffic and Highway EngineeringCivil EngineeringISBN:9781305156241Author:Garber, Nicholas J.Publisher:Cengage Learning