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Chapter 8: Left Turn Phasing—Permitted, Protected, or Both
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The purpose of this activity is to give you the opportunity to learn about protected plus permitted left turn
phasing.
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Describe the trade-offs and relative efficiencies between protected plus permitted and protected left
turn phasing
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Movie file: A49.wmv
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Prepare a document that includes your answer to the Critical Thinking Question
As you begin this activity, consider the following question. You will come back to this question when you
have completed the experiment.
1.
Why do the eastbound left turn and westbound left turn movements have lower delay when they are
operating as protected/permitted phasing as compared to the protected left turn case?
In the previous activity, you considered permitted and protected left turn phasing. Protected left turn
phasing offers some benefits over permitted left turn operations, such as reduced left turn delay when
opposing through volumes are high, but at the expense of increasing delay for other movements. In
this activity you will consider another type of left turn treatment, protected plus permitted phasing.
In this type of treatment, left turn movements have two separate green intervals, protected operations
followed by permitted operations.
Protected plus permitted phasing is shown in the ring barrier diagram in Figure 168.
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Comparing Protected/Permitted and Protected
Left Turn Phasing