No abstract

Nonattainment areas taking advantage of EPA’s modified enforcement of the 1990 Clean Air Act mandates for unpopular emissions control measures will be required to identify alternative measures to reduce emissions, and several areas have indicated their intention to implement scrappage programs for older vehicles as a means of “replacing” the emissions reductions originally expected to result from these other measures. The potential reductions in fleetwide motor vehicle emissions from scrappage of all older light-duty vehicles in a typical urban area’s fleet are analyzed, and the sensitivity of those reductions to the timing of the program’s implementation and to alternative assumptions about more intensive use of vehicles remaining in the fleet are explored. The cost-effectiveness of such a program in reducing ozone precursor emissions is investigated and the reliability of estimates of the program’s effectiveness developed by using the MOBILE5a vehicle emissions model are evaluated. The likely emissions reductions from even so comprehensive a vehicle scrappage program cannot replace those anticipated to result from measures such as enhanced inspection and maintenance and sales of reformulated gasoline, but smaller-scale retirement programs may be a cost-effective element of a larger package of emissions reduction strategies.

Soak period distribution is a key input for modeling the emissions factors for mobile sources. Methods for deriving soak period distributions from travel survey data are discussed. Data from the 1995 Nationwide Personal Transportation Survey (NPTS) were analyzed to derive soak times. Detailed analyses were conducted to relate soak time variability to geographic, trip-purpose, and time-of-day variables. The findings reinforce the prevailing general guidance on inputs to modeling the emissions from mobile sources. That is, whenever possible, local data should be used to derive soak distribution inputs to the emissions models. Alternatives are offered to accurate but more expensive local surveys as well as to the roughly aggregate and potentially inaccurate national defaults on soak period inputs to emissions factor models such as MOBILE6. On the basis of a detailed statistical analysis, a grouping scheme is devised to consolidate soak distribution inputs by time period. The grouping scheme will enhance the utility of survey data in deriving the soak distributions and reduce the effort in providing soak distribution inputs to MOBILE6. The soak periods derived from the NPTS data also can be used for deriving the operating-mode fractions inputs needed for MOBILE5B and modal emissions models.

No abstract

The recent disastrous financial performance of the airline industry is probably thought by many to indicate that deregulation is not workable. But simulations suggest that the current recession and the 1979 fuel price increase are primarily to blame. Deregulation has caused transitional losses for some segments of the industry; but the new freedoms accorded to the airlines probably have helped rather than hurt the profitability of the industry.