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 data

http://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!