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Sub-problem 1a - Page 2 of 8

ID# C101A02

Sub-problem 1a: Analysis of the existing TWSC intersection

Let's discuss each of these issues and how each affects the operational analysis that we are about to complete.

Which tool or tools from the HCM should be used for this analysis? The analysis tools for unsignalized intersections are contained in chapter 17 of the HCM 2000. Chapter 17 includes analysis tools for two-way stop-controlled (TWSC) intersections, all-way stop-controlled (AWSC) intersections, and roundabouts. In this analysis, we will use the procedure for TWSC intersections. Since we are interested in existing conditions at the intersection, at a fairly detailed level, we will use the operational analysis procedure in chapter 17.

What data are required for the analysis? Since we are interested in determining the average control delay that drivers experience at the existing intersection, we will use the operational analysis method that is included in chapter 17 of the HCM. The following data are needed to conduct an operational analysis:

bullettraffic volumes for each movement
bulletnumber of lanes and lane configuration for each approach
bulletproportion of heavy vehicles
bulletpeak hour factor
bulletgrades on each approach
bulletother geometric features (channelization, medians)

We should note one potential point of confusion in the aerial photograph for this intersection. While the eastbound approach striping does not show this explicitly, this approach does operate as if it is configured with an exclusive left turn lane and a shared through/right turn lane.  These details are always important to check in the field.

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