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Sub-problem 5a: Two-Phase Traffic Signal Control

The application of the QEM sneaker check to this sub-problem is summarized as follows:

Exhibit 3-37. QEM Results Summary
Left turn volume 120 vph
Left turn equivalence 9.6 (i.e., > 3.5)
Cycle length 120 sec
Cycles per hour (3,600/120) 30
Capacity at 2 veh/cycle 60

So, the QEM sneaker check also suggests the need for a protected left turn.

The operational procedure offers the perspective of delay and v/c ratio for the left-turn movement. These more detailed performance measures are beyond the scope of the QEM. Applying the operational procedure using the signal timing plan given by the QEM, we see the following results for the WB left turn:

Exhibit 3-38. Operational Procedure Results Summary
v/c ratio 1.02
Control Delay per Vehicle 98 sec
Level of Service F

These results confirm from three different perspectives that a signal operation is unlikely to accommodate the westbound left turn satisfactorily without a protected phase. The next sub-problem will examine a three-phase operation with protection for this movement.

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