Estimating vehicle operating costs (VOCs) allows individuals and organizations to make informed decisions about vehicle usage. As a wide variety of cars and roadway conditions exist, a relatively large amount of input must be provided to any VOC model. Developed as part of a civil engineering research project funded by the U.S. Department of Transportation, five VOC models were run initially in Microsoft Excel. While this early solution was practical and operational, to improve usability, including efficiency of data input, flexibility of running the models, and presentation of results, an alternative solution, a web-based application, was also designed and implemented. The VOC models that can be run on both Excel and the web-based application are: fuel economy, oil consumption, tire wear, mile-age-related vehicle depreciation, and repair and maintenance. This paper briefly introduces the VOC models, describes the two software interfaces created for running them, and presents the results of a user study conducted to evaluate and compare the two interfaces. The study involved 17 participants and focused on usability characteristics and the quality of the user experience. The independent variable was “user interface,” with two test conditions: Excel interface and web-based interface. The participants answered an entry questionnaire, performed tasks using both interfaces, and completed an exit questionnaire. Several dependent variables were measured and analyzed, including task completion time, number of incorrect data entries, and number of clarification questions asked to the user study facilitator. The results obtained showed that the web-based solution consistently outperformed the Excel-based solution, although the latter received some positive feedback as well.
