This proposal is in response to the California Energy Commission research for advanced transportation technologies with renewable energy (AB118/8) that innovate a wide range of efficiency of engines with advanced emission control and aftertreatment technologies to enable or exceed current Tier 4 emission standards. UCR is teaming with Gradstein and Associates for a comprehensive approach and evaluation of NG technologies as they relate to off-road applications. The project will test the emission and operational performance of natural gas and RNG fueled yard hostlers alongside various yard hostler technologies, including electric and (Tier 4 final) diesel. The natural gas hostlers will be powered by 9 liter NZ engines (already funded) and 6.7 liter 0.1g NOx engines. The project will test fossil natural gas and various blends and sources of renewable natural gas, brought to the site from physical RNG production plants in both LNG and CNG form. To use CNG on the yard hostlers, CNG fuel systems will be required to be fitted on some of the hostlers. The fuel gas sensor will be integrated into an engine to measure gas quality (and make engine adjustments). Well-to-wheel analysis can be considered or the various fuel pathways. The existing funding of the 20 LNG yard hostlers will allow for significantly more extensive testing via this CEC PON award as the funds do not have to be spent on expensive hardware.