ScrapFrac: % of failed vehicles that are scrapped

Early scrappage of problem vehicles results in emissions reduction, if the replacement vehicles generate less emission. For simplification, “I/M Design” does not account for replacement vehicle deterioration, and all replacement vehicles are assumed to pass I/M two years following their purchase.

Upper: 13.3%

Lower: 6.7%

5% (0% - 10%) for motorcycles, 2.5% (0% - 5%) for light duty trucks, 0.5% (0% - 1%) for buses and heavy trucks (Triangular distribution)

A World Bank study [10] predicts that 5% of failed motorcycles will be scrapped. This result indicates that the early scrappage rates attributable to I/M programs may be lower in developing countries than in developed countries. 5% is applied to motorcycles in this study, and a 2.5% scrappage rate is assumed for light-duty trucks and 0.5% for buses and heavy trucks, given that these vehicles are generally more expensive and thus less likely to be scrapped.

VehWaive: % of identified problem vehicles waived by an I/M program

I/M design in the U.S. generally allows some fraction of problem vehicles to be waived from the programs, usually because of economic hardship.

Upper: 1%

Lower: 4%

1% (0-2%, uniform)

In Bangkok, the government may also consider waivers in the implementation of I/M programs. In particular, for public transit such as buses, high repair costs are likely to result in significant increases in bus fares, which may prevent low income people from using them. However, given the severity of the air pollution problem in the area, a high waiver rate should be restricted. A 1% waiver rate was assumed for all vehicle types.