Without Model
Without an existing traffic model, the interchange justification procedures
requires the following of the GIS-based Quick Model Building Technique
outlined in the bypass section of this guide. Following the links provided
below will take the user to the information on bypass analysis and small
area model development. Note that for the interchange justification, the
model needs to be developed and run through Tranplan for the original
assignment and modified to represent the interchange and run through Tranplan
to retrieve the ramp volumes.
Following the model development methodology, a MapBasic program has been
written to assist in the updating of the network to represent the interchange.
The program allows the user to digitize new nodes and links to represent
the interchange location and then automates the process of updating coordinate
values, node numbering, distance calculations and enters default speeds
and capacities.
This program can be very useful as the policy considerations indicate
that all feasible alternative without and different alternative with the
interchange need to be examined. A recommendation is to develop each alternative
as a separate directory where the modeling is performed. This will help
structure the model runs and help avoid potential losses in results or
confusion about which results are for which alternative.
As for the socio-economic modification to the network, the user needs
to change the productions and attractions around the new interchange to
accurately reflect the amount of development that is expected to occur
in the area as a function of the new interchange. This step is very important
because one of the policy considerations looks at making sure that the
land-use entered for the alternatives is reasonable.
At this point, the user can either continue and examine the GIS-Traplan
analysis or the HCS analysis.
Select any of the options to receive more
information or click on the continue to bypass analysis for instruction
on developing the model or click on the back button to return to the main
interchange justification page or the site map button to go to the site
map.
