Civil Engineering Reference
In-Depth Information
Chapter 15
Managing Nonrecurring Congestion
15.1 Introduction
Nonrecurring congestion accounts for over half of all traf
c delays in the United
States [
1
] and accounts for up to 2/3 of traf
c delays in urban areas larger than one
million population [
2
]. Therefore preventing and reducing the impact of nonre-
curring congestion is a key strategy for improving traf
c conditions.
c delays from nonrecurring events have
emerged in recent years, and they are now receiving the same level of priority given
to strategies that address recurring congestion.
These nonrecurring strategies are keyed to the type and causes of delay
Various strategies for addressing traf
—
whether delays are caused by incidents (e.g., crashes, vehicle breakdowns), work
zones, special events that generate surges in traf
c demand, inclement weather, or
construction zones, and major evacuations.
To effectively minimize the adverse road user impacts of nonrecurring con-
gestion requires the use of accurate real-time information that enables transportation
agencies to proactively and quickly respond to changes in traf
c conditions caused
by incidents, adverse weather, road maintenance, or random surges in traf
c
demand from special events. These changes can consist of traveler advisory
information in maintaining safe speed, lane changes, or dynamic traf
c control
policies that minimize delay, and that inform travelers about the location and extent
of congested conditions. Real-time information is a major bene
t of Intelligent
Transportation Systems (ITS) technology that enables the emerging practice of
Active Transportation and Demand Management (ATDM) [
3
].
