Next Article in Journal
Analysis of Manufacturer Plug-In Electric Vehicle Incentives
Previous Article in Journal
Experimental behaviour of Li-ion and supercapacitors cells for HEVs under standardized and tailored-life cycle testing
World Electric Vehicle Journal is published by MDPI from Volume 9 issue 1 (2018). Articles in this Issue were published by The World Electric Vehicle Association (WEVA) and its member the European Association for e-Mobility (AVERE), the Electric Drive Transportation Association (EDTA), and the Electric Vehicle Association of Asia Pacific (EVAAP). They are hosted by MDPI on as a courtesy and upon agreement with AVERE.
Open AccessArticle

Heavy-Duty PHEV Yard Tractor: Controlled Testing and Field Results

Vehicle Test Engineer, Southern California Edison, Pomona, California, USA
Manager, Electric Drive Systems, Southern California Edison, Pomona, California, USA
Author to whom correspondence should be addressed.
World Electr. Veh. J. 2012, 5(1), 246-253;
Published: 30 March 2012
PDF [238 KB, uploaded 17 May 2018]


Diesel powered tractors are used to shuttle cargo trailers from point to point within the confines of a port facility, terminal or warehouse yard. Such operations are similar to those in ground support applications at airports and in industrial warehouses with lift trucks, in that the vehicles are used as tools to move goods in a semi-regular pattern. Southern California Edison Company (SCE) and the Electric Power Research Institute (EPRI) have partnered to help electrify vehicle operations in both of those venues with great success and see good prospects for the same at port operations. However, current port operations might require large investments in infrastructure and operational changes to implement electric drive all at once. To help demonstrate the benefits of electric drive without requiring large-scale changes, a plug-in hybrid electric vehicle (PHEV) yard tractor design was proposed by EPRI and member utilities as a means to reduce operational emissions and diesel fuel use. Four member utility companies with large port customers in their service area (SCE, Southern Company, CenterPoint Energy, and New York Power Authority) agreed to work with EPRI to study the benefits and impacts of a PHEV yard tractor. In 2007 the Electric Power Research Institute (EPRI) contracted US Hybrid Corporation (USH) to design and construct a unique PHEV yard tractor. SCE agreed to test and evaluate the PHEV yard tractor for EPRI. To properly evaluate the benefits realized by the yard tractor in comparison to unmodified conventional yard tractors as well as other alternative fueled tractors, SCE had to test the tractor in controlled conditions with realistic loads in addition to field testing. SCE developed test procedures for controlled testing and for field evaluation. The field testing was conducted in four ports across the United States, each with different operating conditions and climate: Long Beach, California; Houston, Texas; Savannah, Georgia; and New York City. SCE designed a test procedure that simulates an accelerated duty cycle of cargo operations. The accelerated duty cycle has multiple starts and stops and little idle time. SCE measured the idling fuel consumption separately so it can be inserted to match the duty cycle of any particular port. The test cycle was performed with the vehicle both unloaded and loaded to profile the effects of load on system efficiencies. SCE also tested the battery and charger performance of the PHEV, and as a comparison, tested an unmodified yard tractor. In the accelerated testing, SCE found the PHEV fuel savings were as high as 60% (on a per-cycle basis) when compared to a stock diesel Kalmar tractor, and up to 35% fuel savings versus operating the PHEV tractor as a hybrid (i.e, not charging it), In charge sustaining operation, the fuel savings are as high as 40% compared to the stock vehicle. On a daily-operation basis, the projected fuel savings on a duty cycle similar to the SCE test cycle could be as low as 35% but as high as 60% with significant amounts of idling and low speed operation. The field test results show good fuel economy but are complicated by reliability issues that reduced the operational time of the prototype PHEV vehicle. Also, it was difficult to get fleet fuel use data. It was the intention in the project to compare the test vehicle’s results with the fleet average fuel use per unit time. These results will be discussed in the body of the paper. Port operators, in general, appreciated the engineoff mode’s reduced noise and exhaust. The US Hybrid prototype PHEV yard tractor has the potential to significantly reduce fuel consumption, as demonstrated in the SCE tests. Performance issues with the prototype prevented full duty in the field tests. Further testing, with a more reliable vehicle incorporating the key system improvements learned from this project, is worth pursuing to determine if the potential fuel savings can be fully realized in larger scale. Furthermore, the techniques and testing methods described can be used for other alternatively-fueled yard tractors.
Keywords: Southern California Edison; EPRI; non-road; yard tractor; PHEV Southern California Edison; EPRI; non-road; yard tractor; PHEV
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

Kellogg, E.; Smith, J. Heavy-Duty PHEV Yard Tractor: Controlled Testing and Field Results. World Electr. Veh. J. 2012, 5, 246-253.

Show more citation formats Show less citations formats

Article Metrics

Article Access Statistics



[Return to top]
World Electr. Veh. J. EISSN 2032-6653 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top