DRAFT Comprehensive Transportation Plan Update: February 23, 2018 version

EXISTING

CONDITIONS

Modeled Traffic Congestion Sophisticated models can simulate the interaction of estimated demand and available supply at a regional scale. The Triangle Regional

Model comprises both the Raleigh urbanized area and the Durham-Chapel Hill urbanized area. For the purposes of this Existing Conditions

Summary, current congestion levels are derived from the Triangle Regional Model 2010 Base Year Model and are symbolized in Figure 2-

17 based on volume-to-capacity ratios. The model represents the roadway network and traffic volumes as they were in 2010 and does not

necessarily reflect the impact of intersections and railroad crossings on traffic congestion. Actual congestion near these locations may be

greater than what is shown in the travel demand model. However, modeled traffic congestion provides systems-level insight into overall

congestion issues and can indicate corridors that warrant higher levels of study and analysis. The information provided in Table 2-4

provides an overview of volume-to-capacity ratios and descriptions of each category.

Table 2-4: Understanding Volume-to-Capacity Ratios

CATEGORY

DESCRIPTION

A roadway with a V/C less than 0.50 typically operates with free-flowing conditions and is underutilizing available roadway capacity.

Very Below Capacity V/C < 0.50

A roadway with a V/C between 0.50 to 0.85 typically operates with efficiency and is not considered congested.

Below Capacity V/C = 0.50 to 0.85

As the V/C nears 1.0, the roadway is becoming more congested. A roadway approaching congestion may operate effectively during non-peak hours but be congested during peak travel periods.

At Capacity V/C = 0.85 to 1.00

Roadways operating at capacity or slightly above capacity are heavily congested during peak periods and moderately congested during non-peak periods. A change in capacity due to incidents greatly impacts the travel flow on corridors operating within this V/C range.

Above Capacity V/C > 1.01

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