|
Sub-problem 5a - Page 1 of 3 |
ID# C405A01 |
Sub-problem 5a:
Network Simulation
Step 1. Setup
VISSIM is the traffic
simulation package we chose to use, so the specific input data files reflect the
needs of that software. However, many of these characteristics and inputs
would be required for other modeling software as well. A summary of the inputs
and assumptions we used is as follows:
 |
network
configuration (highway sections and their connections) |
|
link distances set
to values obtained from the local MPO (Metropolitan Planning Organization)
accurate to the nearest 10 feet |
|
geometrics for all
highway segments |
|
freeway free-flow
speed density functions set to a minimum of 50 mph and a maximum of 60 mph |
|
ramp speed density
functions for the loop ramps, etc., set to a minimum of 22 mph and a
maximum of 28 mph |
|
ramp speed density
functions for the right-hand ramps and semi-direct ramps set to a minimum
of 43 mph and a maximum of 48 mph |
|
ramp speed density
functions for all remaining facilities set to a minimum of 27 mph and a
maximum of 35 mph |
|
trip matrix using
locations A through M in Exhibit 4-78 as
the origins and destinations |
|
heavy vehicle
percentages set nominally at 5% throughout the network |
The O-D trip matrix
was obtained from the Capital District Transportation Committee (CDTC), which
serves as the local MPO. The matrix is derived from the outputs of the
travel forecasting model that CDTC uses in all of its planning studies.
Since it is generated data rather than observed volumes, we do not expect
exact matches between the traffic volumes observed in the field and those
predicted by the O-D trip matrix. The traffic volume on a given link in a
given time period predicted by the O-D trip matrix may be different from the
value that was actually observed in the field. The difference is that the
predicted value uses a routing algorithm to assign flows to network paths
that might not be consistent with the way drivers choose routes.
Consider:
|
What type of output or measures of effectiveness might
we expect to obtain from simulation models that would provide value above
and beyond using HCM methodologies? |
|
How does a
simulation model help develop engineering solutions? |
Discussion:
 Take
a few minutes to consider these questions. Click continue when you are ready
to proceed.
[
Back ] [
Continue ] with Sub-problem 5a |
