Sub-problem 1c - Page 2 of 9
Sub-problem 1c: Analysis of
Let's consider the answers to these questions.
What is the appropriate future year for this analysis? The appropriate horizon for a future year analysis depends on a number
of factors. Often, an agency has a standard target year (based on a
regional travel demand model) on the order of five,
ten, or twenty years. Sometimes the horizon is selected based on the
level and type of the investment under consideration. For a major
freeway investment, twenty years is often used. For a new signal
installation, ten years is often used. We will use a ten year horizon
for this analysis.
Which default values should be used for this future
analysis? While we can take field measurements to determine the
appropriate input data and default values to use for the analysis of
existing conditions, this is not possible for a future analysis. What we
must do is to use the existing data as a guideline and then, based on what we know
about the projected changes in traffic conditions and in the transportation
system itself, make estimates of these future values.
For the analysis of future conditions at the intersection, we must
also consider how to establish reasonable values
for other critical analysis parameters. For an unsignalized intersection
analysis, the additional critical parameters include peak hour factor, critical gap, follow
up time, and heavy vehicle percentage. For a signalized intersection
analysis, these critical parameters include arrival
type, saturation flow rate, peak hour factor, and heavy vehicle percentage.
[ Back ] [
Continue ] with Sub-Problem 1c