Question #$3[60$ pts total$]$ Question #$3$a $[20$ pts$]$

Identify $($list$)$ the critical lane groups for each phase and determine the sum of the flow ratios for

the critical lane groups.

Question #$3$b $[10$ pts$]$

Determine both the minimum cycle length $(C_{\text{m}\text{i}\text{n}})$ and the Webster optimal cycle length $(C_{\text{o}\text{p}\text{t}}).$

Round both cycle lengths up to the nearest $5$ seconds.

Question #$3$c pts

An isolated, pre$-$timed signalized intersection with $1$ left$-$turn lane and $1$ through$/$right$-$lane on each

of the four approaches has the following timing phase plan. The volumes $($arrival rates$)$ for each

movement, and the phase plan are shown in the following image.

For each phase, the startup lost time is $2\mathrm{.}5$ seconds and the clearance lost time is $1\mathrm{.}5$ seconds. The

speed of traffic is $40$ mph on all approaches, the design vehicle is $20$ ft $,$ all lanes are $12$ ft wide,

and all approaches are on a level grade. The desired degree of capacity utilization is $0\mathrm{.}95.$ The

saturation flow rates for each movement are shown in the following table.