左弯待转区

Case 4
* t tu * N Q2
Because t*>tu , the left-turn queue has exceeded the capacity of left-turn lane before starting into waiting area entirely, i.e. the spillback occurs.
The queue of left-turn vehicles overflows the leftturn lane during gT time.
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Left-turn queue accumulation polygon (case 3)
N Q2
There is no spillback occurred.
Meanwhile, due to N*<Q2 , some leftturn vehicles move into the left-turn lane, some residual vehicles remain outside. The spillback continues to the end of gT. The setting of WAFLT does not avoid spillback.
Case 2
* t tu * N Q2
Before the left-turn vehicles overflow the left-turn lane, the left-turn queue forming during tr has started into the waiting area, which indicates that the capacity of leftturn lane increases to N*.
For conflict point 1
Longer signal interval time
tTt ts t Lh ta1
For conflict point 2
t Lt ts tTh ta 2
Minimum green time
New condition
g L min tLt ts t ta 2
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WAFLT
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The contrast of non-spillback and spillback at approach A
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Left-turn queue accumulation polygon (case 1)
However, due to N*<Q2 the left-turn queue overflows the left-turn lane after t*u. The duration of left-turn spillback de to setting WAFLT.
WAFLT
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The rule of WAFLT

Lagging protected left-turn phase When the green time of through phase begins at the same approach, the left-turn vehicles start to run into the waiting area for left-turn and wait to complete their turning movement in green time for left-turn.
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The change after setting WAFLT
Case2
Case1
Case3
Case4
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The sketch of conflict points
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Timing condition（绿尾滞留）
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Analysis on Waiting Area for Left-turn
Vehicles at Signalized Intersections
Yongheng Chen, PhD Transportation Colloege Jilin University The People’s Republic of China cyh2009@
N Q1
The queue of left-turn vehicles overflows the leftturn lane during tr time.
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Left-turn queue accumulation polygon (case 2)
Q1 N Q2
* L
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THANK YOU
Case 1
Before the left-turn vehicles overflow the left-turn lane, the left-turn queue forming during tr has started into the waiting area, which indicates that the capacity of leftturn lane increases to N*.
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Outline

What’s WAFLT Left-turn spillback After setting WAFLT Timing condition
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What’s WAFLT



A new type of channelization Increasing use Lack of methods to design and analyze them
* t tu * N Q2
Meanwhile, due to N*≥Q2, the queue of left-turn does not spill back and other vehicles release smoothly during the gT time. The spillback problem is solved by setting WAFLT.
Case 3
* t tu * N Q2
Because t*>tu , the left-turn queue has exceeded the capacity of left-turn lane before starting into waiting area entirely, i.e. the spillback occurs. Moreover, due to N* ≥ Q2, all of leftturn vehicles overflowed the left-turn lane moved into WAFLT after t*. The spillback ends. The duration time of left-turn spillback decreases to (t*-tu) due to setting WAFLT.