Preventive Maintenance Intervals for Transit Buses (2010)

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41 INTRODUCTION This chapter summarizes conclusions, presents lessons learned from this synthesis project, and offers areas for further study. Material drawn from this work highlights the importance of developing a preventive maintenance (PM) program that considers approaches and information from several sources, but ultimately is one that meets the unique requirements of each agency. The chapter is organized in three sections: 1. Conclusions 2. Lessons Learned 3. Future Study. The future study needs offered at the end of this chapter focus on providing agencies with additional tools and resources to help enhance their PM programs. CONCLUSIONS This synthesis revealed that it takes a substantial amount of insight, ability, and experience to establish service intervals and carry out inspection, repair, and overhaul activities in such a way that the collective actions are effective at prevent- ing minor mechanical issues from resulting in mechanical breakdowns that disrupt passenger service. Given that nearly a half million service interruptions occur annually in the United States owing to mechanical failures, no PM opera- tion, regardless of how effective, will ever fully eliminate them. However, a PM approach that monitors unscheduled maintenance, determines underlying causes, and schedules activities to prevent them will improve bus reliability and customer satisfaction. Investigations made through this study make clear that agencies with effective PM programs are those that direct as much maintenance activity as possible into scheduled events where labor, parts, and vehicle downtime are anticipated and planned. The opposite is “reactive maintenance,” where emergency repairs are made in a triage setting in hopes of producing the minimum number of buses needed to meet peak service demands. Regardless of how well a PM program is developed and executed, certain factors cannot be controlled. For example, one agency identified and replaced a leaking wheel seal in early stages of failure. The perceptive action prevented the seal from saturating the brake lining, avoiding the cost of replacement and a potential safety incident. However, the new seal was defective and failed within days, resulting in a service interruption after all. Examples such as this cou- pled with new propulsion technologies, FTA requirements that buses operate a minimum of 12 years, and increased ridership in the face of reduced budgets make the job of PM formidable. Maintenance managers do not need this study to tell them how difficult PM is. Based on survey comments received they seek: • An indication of where they stand among other agen- cies with regard to PM intervals and related activities. • Sharing of information, especially examples of how other agencies approach PM. • Additional staff and resources to analyze data and fail- ure trends, and update PM procedures accordingly. • Additional staffing to allow dedicated quality assur- ance (QA) personnel to follow up on PM inspections and ensure all defects have been properly identified and repaired. • Additional software capabilities. • More reasonable PM schedules and specifications from original equipment manufacturers (OEMs). • A request for OEMs to place all vehicle PM requirements in one convenient, easy-to-access reference location. Study findings make evident that each agency approaches PM according to its own fleet makeup, operating conditions, and available resources. Although some approaches are com- mon across the industry, others are mixed. Various methods presented in this study allow agencies to consider them for applicability to their own operation. Collective approaches provided here can also provide a benchmark for others to gauge where they stand within the industry with regard to carrying out PM activities. One area of commonality pertains to bus preventive main- tenance inspections (PMIs), where all responding agencies use mileage-based intervals, with 6,000 miles being the norm. Only one agency is investigating the use of fuel con- sumption as the basis for establishing intervals, whereas another has gone to time-based intervals for its electric trolley bus fleet. There is virtually no common ground with regard to software programs used to schedule and guide PM activities CHAPTER SIX CONCLUSIONS AND LESSONS LEARNED

and only a slight majority is pleased with those programs. Most agencies surveyed base their intervals on the actual mileage of the previous interval, regardless if it was early, late, or on time. Only one survey respondent, Dallas Area Rapid Transit, uses a software program to predict part failures based on life cycles. These predictive tools are more commonly used in aerospace and other resource-rich transportation sectors. Most agencies base PM intervals on OEM specifications to maintain warranty coverage, and continue to follow that interval after warranties expire. All use checklists to guide PM activities, but only half develop ones unique to specific buses and equipment. Nearly all agencies surveyed include some type of pass/fail criteria for carrying out PM activities, and most provide technicians with written job instructions. Regarding the skill level of those performing PMIs, a slight majority use experienced technicians; others use entry-level personnel or a combination of both. Most use the same tech- nician to conduct all aspects of the PM activity as opposed to splitting responsibilities. It is assuring that the vast majority of survey responders have some type of QA measures in place to follow up on PM activities. An assessment of how effective they are at actually reducing unscheduled maintenance, how- ever, was outside the scope of this project. More than one in four agencies responding to the survey have not calculated the time needed to conduct PM activities, making it difficult to accurately determine staffing levels and budgets. Those making the calculations reveal that the mean time needed to conduct an “A” bus inspection is 3 h; 5 h for a “B” bus inspection; 8 h for a “C” bus inspection; 3 h for a heating, ventilation, and air conditioning PMI; and 2 h to conduct a wheelchair lift/ramp PMI. Two of three responders have calculated costs associated with PM. Those making the calculation indicated that the median cost for both parts and labor for conducting common PM activities is $162 for “A” bus inspections; $208 for “B” bus inspections; $448 for “C” bus inspections; $566 for heat- ing, ventilation, and air conditioning PMIs; and $140 for wheelchair lift/ramp PMIs. Only half of reporting agencies issue a parts kit with all needed parts when assigning PM work orders. Fewer than half repair defects noted during PM inspections as soon as they are identified; others reschedule as needed. Half of survey responders need 20% spare vehicles to support PM activities, consistent with the FTA maximum allowance. The percentage is high considering that addi- tional spare buses are needed to compensate for buses out of service as a result of accidents, awaiting parts, or in need of other maintenance activities. Remaining spare ratios reported by survey responders are between 5% and 15%, which is more representative of the actual spare fleet needed to conduct PM. 42 LESSONS LEARNED Synthesis findings convey that there is no one PM approach or formula suitable for all agencies owing to the variations that exist. Each maintenance operation must make use of all available information and then establish PM intervals and related activities tailored to its unique fleet and operating characteristics. Robert Johnson, writing for the National Truck Equipment Association, puts it succinctly: “It’s a com- bination of science with trial and error.” To help agencies enhance their existing PM programs, the following lessons learned from this study are offered: • A monitoring system that clearly distinguishes sched- uled and unscheduled maintenance is essential for benchmarking PM performance and for determining if changes made to the PM program are having a positive or negative effect. • Regulatory requirements and OEM specifications serve as the foundation for establishing PM intervals and activities. Becoming thoroughly familiar with these requirements helps ensure compliance. • Once the foundation PM program is established adjust- ments are best made through analyses of unscheduled maintenance data, specific equipment needs, operating conditions, local environment, and other local factors. Programs that violate legal requirements may result in penalties, whereas straying beyond OEM specifications may violate warranty coverage. Consulting with OEMs before making any changes makes use of their knowl- edge and ensures continued warranty reimbursement. • Effective PM programs are constantly evolving as new information is obtained and operating conditions and fleet equipment change. PM programs that remain stag- nant are most likely inadequate. • Monitoring the completion of PM activities at assigned intervals determines if they are being done according to schedule; a 10% early/late window is considered acceptable. • PM checklists are helpful in guiding technicians through the inspection process. • Unique PM checklists specific to each bus and equip- ment type that are continually updated tend to be more useful than generic checklists that cover a broad range of equipment and provide less detail. • Including as much pass/fail criteria as possible on PM checklists assists technicians in determining what is acceptable for inspection items based on regulatory and agency established requirements. • Printing up-to-date PM checklists just before the PMI ensures that technicians perform their tasks according to current information. • Providing technicians with work instructions helps to properly complete PM inspections, repairs, and other maintenance activities. A sound example is the Central Florida Regional Transportation Authority (LYNX) included as Appendix G.

43 • Skilled technicians are more capable of carrying out PM because of their experience and ability to identify equipment abnormalities. Inexperienced technicians can receive valuable instruction by working alongside experienced mentors. • Involving bus operators as an integral part of the PM program through improved communication with the maintenance department can greatly assist with early fault diagnosis and detection. • Although in its infancy, automated onboard monitoring and data downloads done as part of the service line func- tion provide expert means of identifying bus faults before they can escalate into failures and service interruptions. • QA measures put in place to oversee PM inspections and other activities performed by operators, service line per- sonnel, and technicians help ensure that bus maladies are properly identified and repaired. • A classification system that clearly identifies critical and safety-related defects from more routine ones helps satisfy legal requirements, prioritizes the repair of noted defects, and makes certain that buses with more serious faults are corrected before resuming revenue service. • Tracking of all other defects noted during the PM inspec- tion process (i.e., those that are not critical or safety related) helps ensure that they are repaired before or at the next scheduled PMI to prevent the gradual accumula- tion of defects that eventually leads to fleet deterioration. • Predictive models, software programs, and other analy- sis tools, although not used extensively in bus transit maintenance, can provide assistance in determining opti- mal replacement intervals for key parts and components. • Packaging all replacement parts needed for PMs into one convenient kit maximizes efficiency by not having tech- nicians wait while an order for multiple parts is filled. • Calculating the time and costs associated with each PM activity accurately determines budgetary and staffing requirements. SUGGESTED AREAS OF FUTURE STUDY Four areas of future study are offered as a result of the findings. 1. OEM PM materials consolidated into one concise doc- ument. This could be done by developing standard pro- curement language in APTA’s Standard Bus Procure- ment Guideline document. The request is in response to manufacturers that disperse PM requirements for inter- vals and related tasks throughout several documents, making them difficult to locate. The tendency to scatter PM material is understandable because bus manufac- turers use many different vendors for major bus sub- systems and components. Producing an integral PM document would help agencies more easily locate infor- mation needed for their PM programs. Requests were also made that spare parts and PM documentation be provided in electronic format. 2. An industry-sponsored PM peer review program. Managers have a difficult time assessing their PM programs and lack sources for feedback and guidance to improve overall maintenance performance. Dis- tance between service interruptions or road calls is one measure, ratio of scheduled and unscheduled mainte- nance is another. Research could be directed toward developing a program that would involve experienced maintenance managers traveling to agencies when requested to investigate the PM program, make a peer assessment regarding agency PM performance, and provide suggestions for improvement. The review team would also involve the participation of bus and major component OEMs with direct experience regarding their products to help improve agency PM programs. Although the FTA does some of this through its triennial review process, a targeted review by those experienced in transit bus maintenance would be able to make specific suggestions for improving PM. 3. Staffing level requirements determined for maintenance personnel. Several survey responders also called for additional PM staffing and resources. One way to pro- vide assistance would be to research staff requirements needed to conduct PM. The research could canvass the industry to determine staffing requirements for the entire maintenance operation including PM. No recent studies have investigated bus maintenance staffing requirements. Nor are there guidelines to assist agencies in determining adequate levels based on fleet size, operating conditions, fleet age, level of vehicle technology and electronics, facility locations, or other such relevant factors. Such a document would help maintenance managers secure appropriate staffing to conduct PM. 4. Maintenance data analyzed to assist maintenance man- agers establish more cost-effective PM intervals and related repair activities. Despite available tools, many transit agencies continue to rely on “seat of the pants” intuition to establish PM intervals and activities. A study to assist agencies collect, monitor, and analyze data will allow them to more efficiently determine PM intervals and the preventive measures that take place within those periods.