The bypass analysis portion of the project
is concerned with developing methods for the Iowa DOT personnel
to develop a model and use the model to evaluate a potential bypass
project. Improvements to this area include modeling techniques
that would forecast the number of vehicles expected on the new
facility and display turning movement counts for selected intersections
along the bypass. In addition, the modeling methods would allow
for the evaluation of multiple scenarios (different alignments,
access points and levels of access) quickly and graphically.
The National Highway Cooperative
Research Program defines a highway bypass as an existing roadway
that previously passed through town, splits off before entering
the town, continues around the town and ties back into the previous
alignment on the other side of town (NCHRP 210).
Within the bypass analysis section,
a series of steps were developed to assist user construct traffic
models and develop forecasts of roadways volumes. The first
step is to gather appropriate data sets to support the traffic
model. This is followed by establishing the network structure,
both traffic analysis zones and streets to be included in the
model. After deciding on the network, the network is digitized
using a MapBasic program that guide the user through several
steps. The socio-economic characteristics, and corresponding
productions and attractions are enter for the new network and
the model can then be used to provide traffic forecasts. The
final items include a MapBasic program to develop the bypass
to the network and expansion factors to forecast future traffic
volumes.
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