THE MOVING DYNAMIC NATURE OF PROGRESSION CURVES FOR FREEWAY
INCIDENT RELATED CONGESTION
Neveen ShlayanPhD Student
Transportation Research CenterUniversity of Nevada, Las Vegas
Introduction Incidents on urban freeways Causing congestion and delays in both
directions Secondary impact has been poorly
defined by using static time and length thresholds
Does not cover the full range of effects, Resulting in erroneous datahttp://www.youtube.com/watch?v=q0FIO775hEE
Why Does it Matter? Incident Management Policy Making Studying the overall impact of an incident
Financial Fatalities Productivity
Proper Definition of Secondary Incidents Secondary incidents compose 20 percent
of all nonrecurring events (Federal Highway Administration, FHWA-OP-04-052, 2004)
Outline Thorough study of freeway incidents and
the progression curve Classical progression curves Case study in the Seattle, Washington VISSIM simulations Proposed Novel Progression Curve Conclusion
FACTSTexas Transportation Institute, FHWA-HOP-09-005, 2008
Incidents cause 33% to 60% of all delays The capacity of the facility is reduced by
up to 17% (shoulder only) 63% one lane obstruction 77% two lane obstructions 50% due to “rubbernecking” effect
NHP Average Arrival, Management, and Clearance times for incidents
on the I15 interchange in the Las Vegas Area
Static Thresholds for Secondary Congestion
The maximum queue clearance length and clearance time for the incident
Carlos Sun and Venki Chilukuri Secondary Accident Data Fusion for Assessing Long Term Performance of Transportation Systems. US Department of Transportation, (MTC Project 2005-04):1–38, 2007.
Dynamic Thresholds for Secondary Congestion
It was found that static and dynamic thresholds can vary in incident definitions by 30 percent.
Carlos Sun and Venki Chilukuri Secondary Accident Data Fusion for Assessing Long Term Performance of Transportation Systems. US Department of Transportation, (MTC Project 2005-04):1–38, 2007.
Case StudyThe I-5 and I-405 interchange near Linwood north of Seattle, WA
An accident occurred at 2:55pm
Queue length of 2.3 “rubbernecking”
Progression of the
queue after the incident clearance extends to twelve miles even after an hour from clearance
VISSIM Simulations
Artificially Creating Accidents by Lane Obstructions and Speed Reduction
Simulations Scheme Tracking the locations
of front and back of the queue
In the direction of the accident
In the opposite direction of the
accident “rubbernecking”
Low traffic volume (3000 vph)
Moderate traffic volume (5000 vph)
High traffic volumes (8000 vph)
Four, three, and two lane obstructions
Moving Dynamic Progression Curve
Conclusion
Secondary congestion is highly dynamic
Secondary Incidents definition must be case specific
Future Work• Development of detailed models that
will study all types of secondary congestion based on Shock wave analysis
A software is being built that will process data using the above analysis that will identify secondary incidents mapped to their primary ones
Thank You!