| Summary: | 碩士 === 國立成功大學 === 土木工程研究所 === 86 === By regulating the input volume of a freeway system through
ramp metering, ramp control is a good technique to smooth the
traffic flow on main line and keep the system at a more
efficient level. Although the use of ramp control is not a new
traffic management concept, how to determine the appropriate
metering rates is still unclear. When the overall situation of
the freeway system is complex, determining the metering rates by
making reference to predetermined plots and figures is
questionable. On the other hand, solving the problem purely with
mathematical programming may not appropriately express the time-
space relation of traffic flow. Hence in this research we
propose a time-space networkbased model to solve for a set of
optimal metering rates. In this research, firstly we discuss
the characteristics of dynamic network and formulate our model.
We import a heuristic algorithm, the threshold accepting
heuristic, to solve for vehicle-mile. We use the geometric and
traffic data of Sun Yat-sen Freeway as an example to verify the
model. By adjusting the original traffic data to produce new
demand composition, we alter the long-trip and short-trip demand
at certain interchanges to verify certain properties of the
model. The result indicates that the mode relaxes the metering
rate of those interchangeswhich has more long-trip demand, and
at the same time tightens the metering rate of those
interchanges which has more short-trips as the traffic flow of
long-trip arrived. By limiting the entrance of huge quantity of
short-trip demand, the speed of the main line has been
maintained, thus total vehicle-mile is increased.
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