Development of the MOVES2010b Compliance Factor for Shelby County Tennessee

The IM Compliance Factor used in this analysis was determined in accordance with section 3.10.6 

of the MOVES Technical Users Guide, which states that this factor “accounts for I/M program 

compliance rates, waiver rates, and adjustments needed to account for the fraction of vehicles 

within a source type that are covered by the I/M program”. For areas with I/M programs that are 

administered countywide, the Compliance Factor is defined by the following equation:

Compliance Factor = percent compliance rate times (100 percent minus the percent waiver rate) 

times (regulatory class coverage adjustment percentage)

where,

1. percent compliance rate is the percentage of vehicles in the fleet covered by the I/M 

program that complete the I/M program and receive either a certificate of compliance or a 

waiver.

2. percent waiver rate is the percentage of vehicles that fail an initial I/M test and do not pass 

a retest, but do receive a certificate of compliance.

3. regulatory class coverage adjustmen percentage is percentage of vehicle miles traveled 

(VMT) by the various regulatory weight classes within a source type. Default adjustments 

are provided in Table A.3, pages 46-47, EPA-420-B-10-023, April 2010.

For areas with I/M programs that are not administered countywide, Sean Hillson, of the USEPA, 

OTAQ MOVES Team, provided guidance on how to develop Compliance Factors, as follows:

“The process for adjusting the compliance factor based on the fraction of VMT that occurs in the 

area covered by an IM program is straightforward. If you are modeling an entire county, but the IM 

program only covers some of the vehicles, then the compliance factor can be adjusted according to 

the fraction of VMT that is driven by the covered vehicles:

Assume that 1 million miles are driven by passenger cars (source type 21) in the county and 50% of 

those miles are driven by cars that are covered by an IM program. In this example, the compliance 

factor would be multiplied by 0.5 to correctly estimate the reductions provided by the IM program 

in the entire county. “

In accordance, the components of the compliance factor were developed with the guidance outlined 

above, and then, the result was multiplied by the percentage of vehicles covered by the I/M program 

(I/M split). The SCHD (Shelby County Health Department) compliance factor is defined by the 

following equation:

SCHD Compliance Factor = IM Split x (Compliance Rate x (1 - Wavier Rate) x Regulatory Class 

Coverage Adjustment)

Sample Calculation for sourcetype 11:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 1.00) = 0.5740 or 57.40%

Sample Calculation for sourcetype 21:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 1.00) = 0.5740 or 57.40%

Sample Calculation for sourcetype 31:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 1.00) = 0.5740 or 57.40%

Sample Calculation for sourcetype 32:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 1.00) = 0.5740 or 57.40%
Sample Calculation for sourcetype 42:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.50) = 0.2870 or 28.70%

Sample Calculation for sourcetype 43:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.50) = 0.2870 or 28.70%

Sample Calculation for sourcetype 51:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.50) = 0.2870 or 28.70%

Sample Calculation for sourcetype 52:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.49) = 0.2812 or 28.12%

Sample Calculation for sourcetype 53:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.48) = 0.2755 or 27.55%

Sample Calculation for sourcetype 54:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.50) = 0.2870 or 28.70%

Sample Calculation for sourcetype 61:

SCHD Compliance Factor = 0.6149 x (0.9336 x (1 – 0.0001) x 0.48) = 0.2755 or 27.55%