Page 48 - Undergraduate Research Opportunities Program Proceedings 2017-18

School of Science
Department of Physics

Traffic congestion is caused by many factors, such as the road capacity and the traffic density. Besides the internal
factors, congestion may also be caused by external factors, such as different days of the week, different hours of the day,
and the weather conditions (e.g. the temperature, precipitation, wind speed, visibility). In this study, we collect the data
from Taiwan highway system and The Central Weather Bureau Observation Data Inquire System to investigate the
impact caused by rainfall on the traffic. Among all the weather conditions, we believe that rainfall will cause the greatest
effect on highway traffic. To find out the impact, we will look at how road capacity, traffic density and traffic latency are
influenced by the rainfall.

Supervisor: WONG Michael Kwok Yee / PHYS
Student: SIU Kwong Tai / PHYS Course: UROP1100, Spring
UROP2100, Summer

Hypercongestion is a controversial traffic state in recent studies of congestions. By analyzing the real traffic data from
the Taiwan highway system, we find that hyper congestion exists on some road segments of the Taiwan National
Freeway. In the study, we focus on the speed-flux distribution of highway segments, and some of the features are
consistent with theoretical predictions of the hypercongestion state. In addition, we discuss briefly some possible
reasons that will probably determine the occurrence of hyper-congestion based on some preliminary observations.

Supervisor: WONG Michael Kwok Yee / PHYS
Student: TAI Yee Man / PHYS Course: UROP1100, Spring
UROP2100, Summer

Kerner’s Three-phase Traffic Theory summarizes traffic states into three phases, namely “free flow”, “synchronized flow”
and “wide moving jams”. The theory shows contradictory findings to the earlier fundamental diagram approaches to
traffic studies, in which “synchronized flow” traffic does not lie on the curve of the fundamental relation of traffic flow in
the flow-density plane, but occupies a separate two-dimensional region. To investigate the theory, we attempted to
verify Kerner’s findings using Taiwan real data. Flux-versus-density graphs and space-time diagrams are plotted to make
comparison between real data and the theory, and disagreements are detected. The reasons for the inconsistencies and
limitations of Kerner’s theory are discussed.

Space Orbit Design

Supervisor: WONG Michael Kwok Yee / PHYS
Student: LAU Albert Wai Kit / PHYS Course: UROP4100, Fall

During the design of space trajectories, it is crucial to know where the spaceship can go for a given amount of fuel and
within a time constraint, and this is known as the reachability problem. In ballistic trajectories, the analytical solution of
reachable region exists as function of the initial states. For low-thrust trajectories, the problem of computing the
accurate reachable region in a reasonable time remains unsolved. The low-thrust reachability problem is of interest to
the planning of future missions as many low-thrust missions have been launched in the past two decades and more are
expected in the near future. Previously, a superposition method for estimating the low thrust reachable region is
developed by our team with a greedy optimization method to choose the boundary solutions. The result has been
published in International Astronautic Congress 2017, Adelaide. In this report, a brief summary of the published method
is stated, and some possible enhancements including the polar form superposition algorithm is discussed.

38