Variable name and definition

Variable explanation

Values used in EISINGER20051

Values used in this study (Range, PDF)


PartiRate: % of all vehicles required by I/M participate in the programs

Although I/M programs require all vehicles regulated by the programs to take the inspection process, there may be a certain fraction of vehicles operating illegally without participating in I/M. This variable is not in the “I/M Design” spreadsheet2 PT, but is developed by this study to reflect the levels of participation in the programs in the study area.



(80% - 100%, triangular3)

It has been proposed that the new PM-related I/M programs should be linked to vehicle registrations and managed by a central database in order to significantly improve the levels of participation in the programs. It is expected that, with the government’s strong will and efforts to curb severe air pollution in the BMR, the participation rate of the programs can be high. A mean estimate of 90% participation rate is assumed in this study. However, sensitivity analysis will test the role of this variable on the overall emission reductions by I/M. For simplicity, it was assumed that the fraction of problem vehicles is the same in the participation group as in the “non-participation group”, although in reality, problem vehicles are more likely to escape from the inspection process.

IndenRate: % of inspected problem vehicles that are identified by I/M

Although I/M programs aim at identifying all the problem vehicles (defined as vehicles whose emission rates exceeds I/M testing cut-points) that are inspected, the inherent limitations of I/M make a 100% identification rate unrealistic. It is accepted that some problem vehicles, e.g. 10% of all problem vehicles, will falsely pass I/M.

Upper: 90%

Lower: 71%

50% (0% - 100%, triangular)

This variable reflects the ability of I/M programs to identify problem vehicles. Given that at present the test protocol and program implementation for PM-related I/M programs is not as well developed as that for traditional I/M, and both may be less well developed in developing countries, the identification rates associated with these I/M programs are expected to be lower. Based on this, a 50% identification rate is assumed in this study. In uncertainty analysis, the range of this variable is set to be 0% - 100%, reflecting the worst case that none of the problem vehicles are identified and the ideal case that all problem vehicles are identified.