Empirical Features of Moving Jam Emergence

1
Empirical Features of Moving Jam Emergence

• Chapter 12

2
Agenda

• Pinch effect in synchronized flow
• Strong and weak congestion
• Moving jam emergence in synchronized flow away
  from bottlenecks
• Pattern formation at off-ramp bottlenecks

3
The general pattern type 1

• The downstream front is fixed at the bottleneck.
• The region of synchronized flow is widening
  upstream
• At P speeds sharply decrease, flow decreases,
  leading to an increase in density.
• This self compression is called the pinch effects
  in synchronized flow. Which leads to the
  formation of a pinch region.

4
The general pattern type 1

• Narrow moving jams emerge spontaneously in the
  pinch region.
• Narrow moving jams grow in their amplitude as
  they propagate upstream.
• Some transform into a wide moving jam while
  others disappear.

5
Pinch effect in synchronized flow GP type 1

• The congested pattern can occur only if the
  upstream front of synchronized flow starts to
  propagate upstream.
• A GP appears upstream of the bottleneck if the
  pinch effect is realized within synchronized flow
  upstream of it.

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Pinch effect in synchronized flow Narrow moving
jam emergence

• In synchronized flow in the GP, a pinch region is
  formed where narrow moving jams emerge, and grow
  propagating upstream.
• The upstream front of synchronized flow is
  determined by the location where a narrow moving
  jam has just transformed into a wide moving jam.
• Suppression effect -When a wide moving jam
  occurs, the jam suppresses the further growth of
  a narrow moving jam.

Jlt--S
SF
J
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Pinch effect in synchronized flow Narrow moving
jam emergence
q
All points in the pinch region
3000
1500
0
?
8
Pinch effect in synchronized flow Narrow moving
jam emergence
q
A subset between narrow moving jams
3000
1500
0
?
9
Pinch effect in synchronized flow Limit flow
rate in pinch region

• The decrease in the average flow rate in the
  pinch region has a limit

q
q
6000
6000
D5 day 1
D5 day2
40
40
t
t
0620
0720
0820
0620
0720
0820
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Pinch effect in synchronized flow S?J
SF
J
Can widen and increase
Over time
J
J
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Pinch effect in synchronized flow Flow rate in
GP

• The downstream front of the synchronized flow is
  fixed, however the discharge rate does not depend
  on spatial coordinates.

Nearly constant
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Pinch effect in synchronized flow Flow rate in
GP

• The differences in q(pinch) are correlated with
  the differences in the out flow of a wide moving
  jam q(out) .
• Within the pinch region, we are usually above the
  J line however the flow rates are lower than
  q(out) .

13
Pinch effect in synchronized flow Flow rate in
GP

• The mean time between narrow moving jams Tj , is
  limited by Tj,lim .
• Tj,lim . is correlated with the minimum distance
  between narrow jams and both decrease with the
  average speed of the SF.
• The existence of Tj,lim . , and hence
  the maximum frequency fmax is a saturation effect.

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Pinch effect in synchronized flow Saturation
and dynamics

• The limitation on q(pinch) is a saturation
  feature
• Narrow moving jams emergence is a dynamic feature
  of the pinch effect.
• If the mean distance between narrow moving jams
  in the pinch region and wide moving jams is
  small, some will disappear during their
  transformation into wide moving jams.
• The mean time between the transformation of a
  narrow moving jam into a wide moving jam, is
  almost constant.

Valid only when q(pinch) is in the vicinity of
its limit
15
Strong and weak congestion
16
Strong and weak congestion
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Moving jam emergence in synchronized flow away
from the bottlenecks

• An F?S transition occurs away from the
  bottleneck.
• Later, the pinch effect in SF is observed, in the
  pinch region, a narrow moving jam emerges
  spontaneously.
• The narrow moving jam grows propagating upstream.
  The subsequent growth of this narrow moving jam
  leads to wide moving jam formation.

18
The general pattern type 2

• An F? S transition occurs
• This leads to WSP formation
• The downstream front of WSP is fixed at the
  bottleneck
• Over time the average speed in synchronized flow
  decreases and the density increases leading to a
  pinch region.

19
The general pattern type 2

• Narrow moving jams emerge spontaneously in the
  pinch region.
• Narrow moving jams grow in their amplitude when
  they propagate upstream.
• Some transform into a wide moving jam while
  others disappear.

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Pattern formation at off-ramp bottlenecks

• An F ? S transition usually occurs at some
  distance upstream of the off- ramp bottleneck.
  The downstream front of the GP is also located at
  some distance upstream of the bottleneck.
• In all measurements conducted, GPs have been
  observed at off-ramp bottlenecks only under weak
  congestion conditions

21
Induced F ? J Transition

• An induced F ? J transition can occur when flow
  rate in free flow is greater than the q(out) .
• This induced effect can be observed with a
  decrease in vehicle speed occurs in the off-ramp
  lane of an off-ramp.

22
Induced F ? J Transition
An abrupt decrease in average speed in the
off-ramp lane
?
The local perturbation propagates upstream in the
off-ramp lane
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Thank you for your attention