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I-355 Veterans Memorial Tollway (I-88 to I-55) Congestion and Crash Scans

The Chicago region traffic congestion scans were created by averaging five minute speed data obtained from freeway loop detectors, radar, and mobile technology data. The traffic scans display average speed on a freeway corridor as a function of time of day (the x-axis) and location (the y-axis) along a freeway corridor.

Crash scans show the rate of total highway crashes per 100 million vehicle-miles traveled (VMT) for 1/10 mile segments.  The purpose of these crash scans is to show highway planners and system managers how crashes are related to congestion.  Understanding where crashes are concentrated can help planners and engineers focus on improving those locations with the worst performance.  

Congestion Scans

I-355, Veterans Memorial Tollway from I-55 to I-88 Congestion Scan, 2011. Showing average speed by milepost by time of day. 

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I-355, Veterans Memorial Tollway from I-55 to I-88 Congestion Scan, 2009. Showing average speed by milepost by time of day.

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I-355, Veterans Memorial Tollway from I-55 to I-88 Congestion Scan, 2007. Showing average speed by milepost by time of day.

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Crash Scan

I-355 Veterans Memorial Tollway, I-88 to I-55 Crash Scan, 2008-12. Showing average speed by milepost by time of day.

Performance Data

Non-holiday Tuesdays, Wednesdays, and Thursdays:

South-bound I-355/Veterans Memorial Tollway

Measure 2007 2008 2009 2010 2011
Free-Flow Travel Time
(Minutes)
7.95 8.19 8.25 8.63 8.73
Average AM Peak-Period
Travel Time (Minutes)
8.73 9.05 9.31 9.59 9.40
AM Travel Time Index 1.10 1.10 1.13 1.11 1.08
Average PM Peak-Period
Travel Time (Minutes)
9.07 10.44 9.46 9.98 9.99
PM Travel Time Index

1.14

1.27

1.15

1.16 1.14
AM Peak-Period
95th Percentile Travel Time
(Minutes)

9.22

9.54

10.63

10.49 9.90

AM Peak-Period
Planning Time Index

1.16

1.16

1.29

1.22 1.13
PM Peak-Period
95th Percentile Travel Time
(Minutes)

10.17

13.06

11.02

13.18 11.89
PM Peak-Period
Planning Time Index

1.28

1.59

1.34

1.53 1.36
Congested Hours

4.66

6.09

4.15

4.48 2.77

North-bound I-355/Veterans Memorial Tollway

Measure

2007

2008

2009

2010 2011
Free-Flow Travel Time
(Minutes)

8.21

8.34

7.99

8.53 8.57
Average AM Peak-Period
Travel Time (Minutes)

13.37

15.88

9.74

10.91 10.82
AM Travel Time Index

1.63

1.90

1.22

1.28 1.26
Average PM Peak-Period
Travel Time (Minutes)

8.52

8.90

8.38

8.98 8.92
PM Travel Time Index

1.04

1.07

1.05

1.05 1.04
AM Peak-Period
95th Percentile Travel Time
(Minutes)

24.71

28.81

13.79

18.23 16.27

AM Peak-Period
Planning Time Index

3.01

3.45

1.73

2.14 1.90
PM Peak-Period
95th Percentile Travel Time
(Minutes)

8.84

9.88

8.89

9.52 9.28
PM Peak-Period
Planning Time Index

1.08

1.18

1.11

1.12 1.08
Congested Hours

2.10

3.42

3.92

2.89 2.39

 

About the Data

Data provided by IDOT, Illinois Tollway, and HERE. 

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