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The Texas Department of Transportation (TxDOT) began using an ultra-low-sulfur, low aromatic, high cetane number diesel fuel (TxLED, Texas Low Emission Diesel) in June 2003. They initiated a simultaneous study of the effectiveness to reduce emissions and influence fuel economy of this fuel in comparison to 2D on-road diesel fuel used in both their on-road and off-road equipment. The study incorporated analyses for the fleet operated by the Association of General Contractors (AGC) in the Houston area. Some members of AGC use 2D off-road diesel in their equipment. One off-road engine, two single-axle dump trucks, and two tandem-axle dump trucks were tested. The equipment tested included newer electronically-controlled diesels. The off-road engine was tested over the TxDOT Telescoping Boom Excavator Cycle. The dump trucks were tested using the “route” technique over the TxDOT Single-Axle Dump Truck Cycle or the TxDOT Tandem-Axle Dump Truck Cycle.

The Texas Department of Transportation (TxDOT) began using an emulsified diesel fuel as an emissions control measure in July 2002. They initiated a study of the effectiveness of this fuel in comparison to conventional diesel fuel for TxDOT's Houston District operations and included the fleet operated by the Associated General Contractors (AGC) in the Houston area. Cost-effectiveness analyses, including the incremental cost per ton of NOx removed, were performed. NOx removal was the focus of this study because Houston is an ozone nonattainment area, and NOx is believed to be the limiting factor in ozone formation in the Houston area. The cost factors accounted for in the cost-effectiveness analyses included the incremental cost of the fuel (including an available rebate from the State of Texas), the cost of refueling more often, implementation costs, productivity costs, maintenance costs, and various costs associated with the tendency of the emulsion to separate.

The Texas Department of Transportation (TxDOT) began using an emulsified diesel fuel in July 2002. They initiated a simultaneous study of the effectiveness of this fuel in comparison to 2D on-road diesel fuel, which they use in both their on-road and off-road equipment. The study also incorporated analyses for the fleet operated by the Associated General Contractors (AGC) in the Houston area. Some members of AGC use 2D off-road diesel fuel in their equipment. The study included comparisons of fuel economy and emissions for the emulsified fuel relative to the conventional diesel fuels. Cycles that are known to be representative of the typical operations for TxDOT and AGC equipment were required for use in this study. Four test cycles were developed from data logged on equipment during normal service: 1) the TxDOT Telescoping Boom Excavator Cycle, 2) the AGC Wheeled Loader Cycle, 3) the TxDOT Single-Axle Dump Truck Cycle, and 4) the TxDOT Tandem-Axle Dump Truck Cycle.

The Texas Project was a multi-year study of aftermarket conversions of a variety of light-duty vehicles to CNG or LPG. One aspect of this project was to examine the factors that influence the economics of fleet conversions to these alternative fuels. The present analysis did not include longer-term effects (such as possible increases in exhaust system life or increases in tire wear). Additionally, assumptions were required to estimate the costs of repairs to the alternative fuel system and engine. Other factors considered include conversion cost, fuel prices, annual alternative fuel tax (as applied for the state of Texas), annual miles accumulated, and the percent miles traveled while using the alternative fuel for dual fuel conversions.

The Texas Project is a multi-year study of the emissions and fuel economy of aftermarket conversions of light-duty vehicles, including passenger cars, light light-duty trucks, and heavy light-duty trucks. The test fleet, consisting of 86 mostly 1994 model year vehicles, includes eight different types of light-duty vehicles that have been converted to dual fueled operation for either CNG or LPG and corresponding gasoline controls. Virtually every type of aftermarket conversion technology (referred to as a “kit” for convenience) is represented in the test matrix: eight different CNG kits and seven different LPG kits, all of which have closed loop control systems. One goal of The Texas Project is to evaluate the different kits for each of the applications. One method used for evaluating the different kits was by assessing their potential for attaining LEV certification for each of the vehicle applications.

The Texas Project involves the conversion of light-duty vehicles, up to and heavy light-duty trucks, to bi-fueled vehicles using commercially available aftermarket CNG and LPG conversion systems. The test fleet includes 68 dual fueled conversions. Virtually every type of aftermarket conversion technology for CNG and LPG was evaluated: eight different CNG and seven different LPG conversion “kits”, all of which are modern systems incorporating closed-loop control. The kits were installed and calibrated according to the manufacturer's guidelines and recommendations. The emissions when operating on the alternative fuel were compared to those when operating on certification gasoline to determine the “success” of the conversion. Many of these conversions, performed according to the manufacturer's requirements, were not “successful” (worse emissions than for gasoline operation). In almost all cases, the problem was NOx emissions that were too high when operating on the alternative fuel.

Improved submodels for use in a dynamic engine/vehicle model have been developed and the resulting code has been used to analyze the tip-in, tip-out behavior of a computer-controlled port fuel injected SI engine. This code consists of four submodels. The intake simulation submodel is similar to prior intake models, but some refinements have been made to the fuel flow model to more properly simulate a timed port injection system, and it is believed that these refinements may be of general interest. A general purpose engine simulation code has been used as a subroutine for the cycle simulation submodel. A conventional vehicle simulation submodel is also included in the model formulation. Perhaps most importantly, a submodel has been developed that explicitly simulates the response of the on-board computer (ECM) control system.