Empirical Features of Wide Moving Jam Propagation

1
Empirical Features of Wide Moving Jam Propagation

• Chapter 11

2
Contents

• Characteristic Parameters of Wide Moving Jams
• Empirical Determination of Line J
• Propagation of Wide Moving Jam through
  Synchronized Flow
• Conclusions

3
Characteristic Parameters of Wide Moving Jams

• When outflow is free and control parameters are
  fixed
• Approximately same mean values for different
  jams Downstream front velocity vg, flow rate
  qout, avg. speed vmax and vehicle density ?min in
  jam outflow and density in the jam ?max.
• Maximum possible flow rate in free flow
  qmax(free, emp) can be much larger than qout.

4
Determining line J with empirical data

• Use distance between detectors and time series of
  vehicle speed to determine vg
• ?min and qout are measured in the outflow of the
  wide moving jam.

5
Characteristics of wide moving jams

• Using the J line avg. vehicle density within the
  wide moving jam ?max is estimated from the
  intersection of line J with the x-axis.
• Different characteristics for different lanes
  (same slope vg) because of long vehicles.

6
Dependence on traffic conditions
April 15, 1996
March 23, 1998
Vg
-16
-14
qout
5000
4200
Intense snow fall
7
WMJ propagation through SF
When synchronized flow is formed in the wide
moving jam outflow
qout lt qout
(syn)
?min gt ?min
(syn)
Happens when a WMJ propagates through a region of
SF, e.g. at a bottleneck.
(?min , qout )
(syn)
(syn)
is a point on the J line
8
Conclusions

• Wide Moving Jams propagate through different
  states of traffic while maintaining mean vg.
• To determine the line J only vg and traffic
  variables in the jam outflow are necessary.
• When SF is formed in the outflow, the values of
  traffic variables lie on the line J.