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Data collected along transects are becoming more common in environmental studies as indirect measurement devices, such as geophysical sensors, that can be attached to mobile platforms become more prevalent. Because exhaustive sampling is not always possible under constraints of time and costs, geostatistical interpolation techniques are used to estimate unknown values at unsampled locations from transect data. It is known that outlying observations can receive significantly greater ordinary kriging weights than centrally located observations when the data are contiguously aligned along a transect within a finite search window. Deutsch (1994) proposed a kriging algorithm, finite domain kriging, that uses a redundancy measure in place of the covariance function in the data-to-data kriging matrix to address the problem of overweighting the outlying observations. This paper compares the performances of two kriging techniques, ordinary kriging (OK) and finite domain kriging (FDK), on examining unexploded ordnance (UXO) densities by comparing prediction errors at unsampled locations. The impact of sampling design on object count prediction is also investigated using data collected from transects and at random locations. The Poisson process is used to model the spatial distribution of UXO for three 5000 Â 5000 m fields; one of which does not have any ordnance target (homogeneous field), while the other two sites have an ordnance target in the center of the site (isotropic and anisotropic fields). In general, for a given sampling transects width, the differences between OK and FDK in terms of the mean error and the mean square error are not significant regardless of the sampled area and the choice of the field. When 20% or more of the site is sampled, the estimation of object counts is unbiased on average for all three fields regardless of the choice of the transect width and the choice of the kriging algorithm. However, for non-homogeneous fields (isotropic and anisotropic fields), the mean error fluctuates considerably when a small number of transects are sampled. The difference between the transect sampling and the random sampling in terms of prediction errors becomes almost negligible if more than 20% of the site is sampled. Overall, FDK is no better than OK in terms of the prediction performances when the transect sampling procedure is used.

The first round of Federal Test Procedure (FTP) emissions testing of variable-fuel ethanol vehicles from the U.S. Federal fleet was recently completed. The vehicles tested include 21 variable-fuel E85 1992 and 1993 Chevrolet Lumina sedans and an equal number of standard gasoline Luminas. Results presented include a comparison of regulated exhaust and evaporative emissions and a discussion of the levels of air toxics, as well as the calculated ozone-forming potential of the measured emissions. Two private emissions laboratories tested vehicles taken from the general population of Federal fleet vehicles in the Washington, D.C., and Chicago metropolitan regions. Testing followed the standard U.S. Environmental Protection Agency's FTP and detailed fuel changeover procedures as developed in the Auto/Oil Air Quality Improvement Research Program. Variable-fuel vehicles were tested on single respective batches of E85, E50, and California Phase 2 reformulated gasoline (RFG) blended specifically for this test program.

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The first round of emissions testing of light-duty alternative fuel vehicles placed in the U. S. federal fleet under the provisions of the Alternative Motor Fuels Act was recently completed. This undertaking included 75 Dodge B250 vans, of which 37 were dedicated compressed natural gas models, and 38 were standard gasoline controls. Data were collected on regulated exhaust emissions using the federal test procedures, and on a number of other quantities, through a statistically controlled program of investigation. Fuel economy results were also recorded. All test vehicles were operated in routine federal service activities under normal working conditions, adhering as closely as possible to Chrysler's prescribed maintenance schedules. The data analysis conducted thus far indicates that the compressed natural gas vehicles exhibit notably lower regulated exhaust emissions, on average, than their gasoline counterparts, and that these values are well within U.S. Environmental Protection Agency standards. In addition, lower levels of toxic constituents are emitted by the compressed natural gas vehicles relative to their gasoline counterparts, and they produce lower levels of ozone precursors as well-both characteristics that are highly desirable in contemporary transportation fuels. The compressed natural gas vehicles obtain slightly lower fuel economy than their gasoline counterparts on an energy equivalent basis. To promote the use of alternative fuels and development of an alternative fuel vehicle (AFV) industry, the Alternative Motor Fuels Act (AMFA) of 1988 requires the U.S. federal fleet to include as many AFVs as practicable. The Energy Policy Act (EPACT) of 1992 tightened the requirements for the federal fleet, requiring new vehicle purchases to be comprised of an increasing percentage of AFVs, up to a maximum of 75%, by 1999. The U.S. Department of Energy is responsible for tracking and reporting the performance of these vehicles on an annual basis to facilitate ongoing evaluation of AFV technology, and for assessing the viability of AFVs in commercial and private applications. Performance measures include driver acceptance, fuel economy, operational cost, cost and level of maintenance, and emissions output. The most extensive effort of its kind, the AMFA evaluation program targets three alternative fuels-methanol, ethanol, and compressed natural gas (CNG)-and encompasses several different types of vehicles, makes, and models operated in a number of federal service applications at various sites around the country. Light-duty passenger cars, vans, and trucks are included, along with school buses, transit buses, and heavy-duty trucks. The earliest AMFA vehicles have been in service since 1991. One of the objectives of the AMFA light-duty test program is to compare the emissions of AFVs in actual service to those of otherwise identical vehicles operating on conventional fuel. Detection of emissions deterioration as a result of age and use is of particular interest. In all cases, reformulated gasoline (RFG) is used...

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