Sub-problem 1b: Maxwell Drive PM Peak Hour - With Conditions

In Scenario C-3 we’ve tested to see what happens if the throughs and rights are erroneously grouped together for the north and southbound approaches, thus assuming that some of the right turning vehicles will be in the through lane. You’ve created a double-right where the second right-turn lane is co-mingled with throughs. That’s a very uncommon (but not impossible) condition. In Scenario C-4, we’ve taken advantage of the fact that we have separate lanes for the northbound and southbound rights and had them move concurrent with the eastbound and westbound lefts. By doing this, we can accommodate all of the northbound and southbound lefts while the eastbound and westbound rights are moving. That means the signal timing for the northbound and southbound through-and-right movements (4 and 8) only needs to provide green time for the northbound and southbound through movements, not the rights. (The difference is 90 instead of 150 vehicles per hour northbound and 60 instead of 195 vehicles per hour southbound.)

Scenario C-5 puts the westbound right turns in a separate lane. This shrinks the westbound total volume and closely matches it to the eastbound through-and-right volume. The eastbound and westbound flows are more similar and the cycle length can be shortened. Scenario C-6 puts the northbound and southbound through-and-right movements in a single lane. The cycle time jumps to 204.9 seconds. In Scenario C-7, we offset that increase in demand for green time by providing double left turns northbound and southbound. The cycle length drops back to 106.7 seconds. Scenario C-8 shows the northbound and southbound approaches are handled in separate phases. We also assumed that the three lanes would be used “optimally” to accommodate the combined lefts, throughs, and rights. Assuming that’s possible, the cycle length drops to the lowest value encountered, 84.4 seconds.