Event Type: PhD Defense

Use of Advanced Traveler Information Systems (ATIS) are considered a
promising way to improve traffic condition by helping travelers to
efficiently use existing transportation facilities. The research
examines a wide variety of information dissemination schemes under
technologies such as in-vehicle navigation systems, changeable message
signs, GPS-based location systems and wireless or Internet based
vehicle communication and routing. This study evaluates various route
guidance systems via static and dynamic network optimization and
traffic simulation models. Parametric studies are conducted on certain
aspects, due to the lack of good models on driver response/compliance
to ATIS information. The dissertation also develops preliminary
insights on networks with multiple information service vendors and the
complex dynamics that result from it. The research methodology
incorporates non-linear network optimization algorithms, heuristic
optimizations as well as traffic network simulation schemes.

The process of activity scheduling is crucial to the
understanding of travel behavior changes. In-depth research is urgently
needed to unearth this process. To reveal this process, a new computer
program, REACT!, has been developed to collect household activity
scheduling data. The program is implemented as a stand-alone program with
Internet connectivity for remote data transmission. It also contains a GIS
for location identification and a special feature that traces the
decisions in scheduling process. A pilot study was conducted in Irvine,
California to evaluate the program performance. Experience from the pilot
study validated the program’s capability of guiding participants to
complete data entry tasks on their own, thus the objective of reducing the
cost and human resource of such a computerized survey is achieved. Other
positive results regarding objectives of reducing instrumental biases and
expanding program capabilities were also obtained. Areas for improvement
were also identified.

Based on the pilot data, activities with shorter duration were found more
likely to be opportunistically filled in a schedule already anchored by
their longer duration counterparts. In addition, the situations (e.g.,
location, involved person, and day of the week) under which an activity
occurred were found related to its scheduling horizon. Analyses were also
performed to validate that the above findings hold in the presence of a
third factor (i.e., in-home vs. out-of-home, and work/school vs.
non-work/school). Additionally, analysis of tour structure reveals that a
certain portion of trip-chains was formed opportunistically. The
proportion of opportunistic stops tends to increase as stop sequence
increase. Travel time required to reach an activity is also positively
related to scheduling horizon of the activity, with distant stop being
planned earlier.

This research describes an innovative distributed approach for the provision of real-time decision support to Transportation Management Center (TMC) operators for coordinated, multi-jurisdictional traffic congestion management on freeway and arterial networks. Coordinated responses among the agencies that share responsibilities for urban traffic management avoids the implementation of operations that may be conflicting or counter-productive.

A distributed software architecture, called CARTESIUS (Coordinated Adaptive Real-Time Expert System for Incident management in Urban Systems) was designed, developed and evaluated. CARTESIUS is composed of two interacting, real-time decision-support systems for TMC operator that are able to perform cooperative reasoning and resolve conflicts, for the analysis of non-recurring congestion and the formulation of suitable integrated control responses. The two agents support incident management operations for, respectively, a freeway and an adjacent arterial subnetwork. Each module interacts with a human operator in one of the agencies, is able to receive real-time traffic and control data, and provides the operator with control recommendations in response to the occurrence of incidents. The multi-decision making approach adopted by CARTESIUS reflects the spatial and administrative organization of traffic management agencies, providing a coordinated solution that attempts to satisfy all parties, preserves their own levels of authority, and reflects the inherent distribution of the decision-making power.

The structure of the distributed processing and the interaction between the agents is based on the Functionally Accurate, Cooperate (FA/C) paradigm, a distributed problem solving approach aimed at producing consistent global solutions even when complete and up-to-date information is not directly available to the agents, in order to reduce communication requirements and synchronization time delays.

The contribution of this research lies in demonstrating the validity of the assumption that satisficing control solutions can be efficiently obtained by relaxing the requirements that agents have shared access to all globally available information, and the application of theoretical principles of the FA/C paradigm to traffic control, through the development of CARTESIUS. The simulation-based validation of the system performance has demonstrated the effectiveness of such an approach in producing real-time, integrated traffic control solutions that reduce the adverse impact of incidents on traffic circulation, network-wide.

A radically new approach which analytically embeds a hydrodynamic flow
model into an optimization framework is developed to solve the dynamic
traffic assignment (DTA) problem. This is the first analytical DTA model
that incorporates simulation equations as constraints to respect the
first-in-first-out (FIFO) requirement in an optimization formulation.
Network assignment is accomplished for the time-dependent
origin-destination demands based on a two-level optimization framework
which fixes the incidence indicator between the time-dependent paths and
their constituent links at one level, and then assigns traffic similar to
a static traffic assignment at the other level. Using this framework,
four DTA models are developed to address different requirements in
ATMS/ATIS. Solution procedures have been designed, implemented and
applied to various networks, including the Anaheim Testbed network, with
considerable success.