Tucson - Pima Association of Governments

Congestion and Pavement Conditions
Roadway Congestion
Volume-to-Capacity Ratio (V/C ratio)
One way to measure roadway congestion is with a roadway
volume-to-capacity ratio (V/C ratio). Congestion levels are defined
as follows:
Severe Congestion: V/C Ratio Greater than 1 (0.56% of VMT in 2010)
Heavy Congestion: V/C Ratio .75 to 1: (4.96% of VMT in 2010)
Moderate Congestion: V/C Ratio .5 to .74: (21.05% of VMT in 2010)
Low to No Congestion: V/C Ratio less than .5: (73.43% of VMT in 2010)
In 2010, about 5.5 percent of total VMT in the region occurred
under heavy to severe congestion conditions, up from 4.5 percent
in 2005.
Note: VMT traveled under heavy to severe congestion is considerably lower than what
was estimated in some past reports, owing to a change in the way in which the V/C
ratio is calculated. Earlier reports, such as the 2000 to 2005 System Performance Assessment,
derived the V/C ratio by using an Average Daily Traffic method to measure
traffic volume, an approach that tends to result in higher congestion level estimates.
V/C ratio is now calculated by modeling peak period and non-peak period volumes
proportional to total VMT, a method that yields a more accurate reflection of actual
travel conditions.
Percent
80
70
60
50
40
30
20
10
0
Roadway Congestion
2005-2010
Low to No
Congestion
Moderate
Congestion
2005
2010
Heavy
Congestion
Severe
Congestion