It can be seen that all but the last three strategies considered would costless than U.S.$2000per ton of NOx reduced.Keeping emission costs below U.S.$2000indicates a very costeffective level based on international experience.From thisbroad analysis，several potential scenarios were developed in the World Bank/SEPAstudy to represent packages of measures for all categories of new vehicles.In selectingstrategies to be adopted，several factors were taken into account，including thefollowing ：旳ir quality need ；昉otential effectiveness of the measure ；旵ostof the measure，including hardware ，maintenance，and fuel economy ；昈verallcost effectiveness；and，echnical feasibility.Considering each of the abovefactors ，the choice of standards that promote the lowest emissions in new vehicleswere narrowed down to the two scenarios summarized in Table 6.The options for finalconsideration were：昐cenario 2：Adopting the standards which were introducedin Europe in 1992followed four years later by the new 1996European standards andcompleting enforcement by 2000.昐cenario 4：Adopting the standards introducedin Europe in 1996and completing enforcement by 2002.Analysts at SEPA determinedthat both scenarios are very cost effective （See Table 7）。After consideringall these factors ，as well as the technological capability of the domestic vehicleindustry，SEPA and its support team recommended S
