Assignment 09 (Solution)

Quick Estimation Input Worksheet.  In this worksheet, you enter all of the input data.  The volume data are given.  The left-turn treatment is given as protected.  The cycle length range is given from 60 to 120 seconds.  The lost time per phase is 4 seconds.

Left-Turn Treatment Worksheet.  Even though we are given that the left turn treatment is protected, using this worksheet (left turn lane check, minimum volume check, and minimum cross product check) shows that protected left turn treatment is not needed.

Quick Estimation Lane Volume Worksheet.  The LT adjustment factor (0.95) is used to modify the left turn volumes.

Quick Estimation Control Delay and LOS Worksheet.  The critical sum is 105 + 250 + 53 + 150 = 558.  The lost time per cycle = 16.  The reference sum  = 1710.  The minimum cycle length is 23.5 seconds, which means that we should use 60 seconds.  The critical degree of saturation is 0.44.  Thus, the intersection is "under capacity".

Increase in demand that can be accommodated?  The critical sum can be increased by 125 percent and the critical degree of saturation would still be slightly below 1.00.