An evaluation of criteria for selecting vehicles fueled with diesel or compressed natural gas

Abstract

We reviewed selection criteria for diesel and compressed natural gas (CNG) fueled vehicles, comparing engine emissions , fire and safety, toxicity, economics, and operations. Diesel-and CNG-fueled vehicles with the latest emission-control technology, including engine-exhaust aftertreatment, have very similar emissions of regulated and unregu-lated compounds, particles through all size ranges, and greenhouse gases. Although toxicity data are limited, no significant toxicity differences of engine emissions were reported. Operating and maintenance costs are variable, with no consistent difference between diesel-and CNG-fueled vehicles. The main operating concern with CNG vehicles is that they are less fuel efficient. Higher infrastructure costs are involved with implementing a CNG-fueled vehicle fleet, giving diesel vehicles a distinct cost advantage over CNG vehicles. For a given budget, greater emissions reductions can thus be achieved with diesel+filter vehicles. Finally, diesel vehicles have a significant fire-and-safety advantage over CNG vehicles. In summary, infrastructure costs and fire-and-safety concerns are much greater for CNG-fueled vehicles. These considerations should be part of the decision-making process when selecting a fuel for a transportation system.