Research On The Methodologies To Evaluate Urban CNG Buses’ Gas Saving Condition

Public transportation is the important way for citizen transportation, and compressed natural gas(CNG) buses are the most important part of urban transportation for large cities. The energy conservation and emission reduction of urban buses already occupied the main part of transportation industry’s research, so the research on urban buses energy-saving evaluation methods can help us diagnose the weak parts of city buses’ energy conservation and emission reduction, and the research is also meaningful for the direction and promotion of energy conservation and emission reduction.Depended on the collected articles, materials and the survey acted in the Sixth Branch Company of Xi’an Bus Corporation, we summarized four traits of urban buses and the influence factors of fuel economy, and we divided the later summary into five parts which are bus conditions, maintaining, driving operations, bus management and traffic conditions. We combined the results above with the selection principles and traits of urban CNG buses, utilized the tower structure of analytic hierarchy process(AHP) to established index level and criterion level, finally we selected 20 indexes and expressed their concepts and calculate formulas. After comparing advantages and disadvantages of every evaluation methodology, we operated two evaluation methodologies to contrast their results, which are the improved information entropy model and the attribute mathematical model.We chose six CNG bus lines of Xi’an Bus Corporation as the examples to proof the two evaluation methodologies, the dates we used in this paper are the company’s whole year operation records of 2013. The evaluation results of these two methodologies are different, this is due to their mathematical differences. Because the improved information entropy model has a better applicability, we chosen this calculate result as the final result of this paper. According to this final result we provided some gas-saving advices for practical operation of urban CNG buses. The final weights’ rank and evaluation result are comparatively accurate to the real condition of these six bus lines, which means our evaluation methodology is reasonable and feasible, and we provided valuable reference frame for the improvement of urban CNG buses’ gas-saving effect.