Po-Yao Kuo Frey, H. C., Kuo, P. Y., & Villa, C. (2009). Effects of idle reduction technologies on real world fuel use and exhaust emissions of idling long-haul trucks. Environmental Science & Technology, 43(17), 6875–6881. https://doi.org/10.1021/es900186e Frey, H. C., & Kuo, P. Y. (2009). Real-world energy use and emission rates for idling long-haul trucks and selected idle reduction technologies. Journal of the Air & Waste Management Association, 59(7), 857–864. https://doi.org/10.3155/1047-3289.59.7.857