Preventive Maintenance Intervals for Transit Buses (2010)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

The objective of every maintenance department is to anticipate repairs and initiate activities that prevent mechanical failures. Transit agencies perform various preventive maintenance (PM) activities at specified intervals to achieve this objective. Some intervals evolve from manufacturers’ specifications and agency experiences; others are simply handed down over time with no real understanding of where they came from. This study examines preventive measures taken by a sampling of transit agencies to ensure buses are on time, protect taxpayer investments, and promote passenger satisfaction and public safety. Effective PM also ensures that buses reach useful service life as defined by the FTA. The approach to this study consisted of a survey questionnaire, literature review, and tele- phone interviews conducted with three agencies as case studies. The survey questionnaire, posted on the Bus Fleet Maintenance listserve, produced 38 agency volunteers from the United States and Canada. Collectively these agencies represent a fleet of 12,062 transit buses, traveling more than 503 million miles annually. A review of the survey responses confirmed that agencies of various fleet sizes are equally represented. The sample is not random; therefore, although it is diverse in terms of size and geography, there is no guarantee that it is representative. Survey responses revealed a mixture of both common and varied approaches to PM. The range is understandable given the variety of bus fleets, assorted onboard bus equipment, and different operating and environmental conditions. Survey responses are summarized here to provide an overview of how agencies carry out bus PM programs to help reduce the nearly half million in-service mechanical breakdowns that occur in the United States annually. • Of survey responders, 92% conduct preventive maintenance inspections (PMIs) on buses between every 2,000 and 6,000 miles, with 71% doing them exactly at 6,000-mile intervals. No agency reported using anything but mileage for this critical PM activity. • Sixty-one percent reset PM intervals based on the actual mileage of the previous inter- val; 39% base them at fixed-point intervals regardless of the previous interval. • Forty-two percent use a window of 10% to determine if PMs are done according to schedule. • Seventy-four percent establish PM intervals to maintain original equipment manufac- turer (OEM) warranty coverage; 82% of them continue to follow OEM suggested inter- vals after warranties expire. • When it comes to using OEM specifications to establish PM intervals, 87% use them for engine oil and filter changes, 71% for transmission fluid and filter changes, 60% for tire pressure and depth, 50% for brake adjustments and wheel lug nut torque, and 45% for brake lining thickness. • All responding agencies use some form of checklist to guide PM activities; 59% use checklists unique to specific buses and equipment; and 41% use generic ones. • Eighty-four percent provide some form of pass/fail criteria for carrying out PM inspec- tions and repairs. • Seventy-nine percent have written instructions for technicians to follow when con- ducting PMIs. SUMMARY PREVENTIVE MAINTENANCE INTERVALS FOR TRANSIT BUSES

• When carrying out PMIs, 60% use skilled technicians, 16% entry-level personnel, and 24% use other skill levels (typically a combination of both skilled and unskilled). • Sixty-one percent use the same technician to conduct all aspects of each PM activity; 39% split responsibilities. • All 38 survey responders reported using some type of software program to schedule and guide PM activities; however, they use 22 different programs. • Software programs that determine optimal part and component replacements based on life-cycle cost calculations are used on an extremely limited basis. • Seventy-four percent have calculated the time needed to conduct PM activities. • Only 63% have calculated costs associated with PM. • The median time needed to conduct the most common PM activities is 3.0 h for an “A” bus inspection; 5.0 h for a “B” bus inspection; 8.0 h for a “C” bus inspection; 3.0 h for a heating, ventilation, and air conditioning PMI; and 2.0 h to conduct a wheelchair lift and ramp PMI. • The median cost (parts and labor) for conducting the most common PM activities is $162 for an “A” bus inspection; $208 for a “B” bus inspection; $448 for a “C” bus inspection; $566 for a heating, ventilation, and air conditioning PMI; and $140 to con- duct a wheelchair lift and ramp PMI. • One-half of survey responders calculate the number of spare vehicles needed to support PM activities, with 55% needing a 20% spare bus ratio. • Fifty-one percent issue a parts kit containing all parts needed for each PM activity. • Seventy-nine percent have quality assurance (QA) measures in place to follow up on PM activities; 41% of them conduct random or spot inspections. • When defects are noted during PMIs, 46% repair them immediately unless parts are not available, 8% make repairs provided they can be done in an established time period, 11% schedule repairs afterwards, and the remaining 35% cite other repair policies. When asked what information, tools, or additional resources would help them establish better PM intervals and programs, agencies responded with several requests: • Sharing of PM information between agencies; • Consolidating all bus PM information into one convenient manual; • More reasonable PM schedules and specifications from OEMs; • Additional staff and resources to analyze data, failure trends, times, etc; • Dedicated QA staff to analyze failures and update PM procedures; and • Additional software capabilities. The literature review produced several definitions for PM that are best summarized as a series of planned actions where labor and vehicle downtime are anticipated, and where the over- riding intent of these actions is to ensure customer satisfaction by providing safe and on-time bus service. The literature review also revealed various U.S. DOT requirements pertaining to bus inspections. Included are driver inspections, periodic inspections conducted by mainte- nance personnel, criteria for determining equipment safety, and recordkeeping requirements. There were several bus-specific publications reviewed on PM that, although dated, pre- sent useful information on predicting replacement intervals for parts and major components, and for calculating life-cycle costs. Modern software programs, however, make parts and component replacements easier to predict. Despite these advances, survey responses indi- cated limited use of these programs. An exception is Dallas Rapid Area Transit, which uses Weibull mathematics to help it decide whether to replace certain parts as a preventive mea- sure in advance of failure. Case studies examined an automated onboard bus monitoring system in use at the Washington Metropolitan Area Transit Authority that automatically downloads fault data as buses enter the service line. Buses actually provide verbal commands by means of onboard speakers to service personnel when malfunctions need immediate attention. Another case study 2

examined a technician certification program established by Whatcom Transit in Washington State to make certain all technicians perform bus inspections in a like manner according to agency-established requirements. The certification program pairs experienced technicians with new hires to ensure they can correctly perform PM inspections. A review was also made of challenges faced by the Central New York Regional Transportation Authority in dealing with its diverse fleet. This agency finds it effective to have each department within its maintenance organization (brakes, electrical, etc.) perform specialized PM inspections and repairs according to detailed, vehicle-specific checklists. Material from this synthesis found that predicting maintenance needs with accuracy is no easy task. Success or failure falls squarely on the ability of the maintenance department to develop and execute an effective PM program. Regrettably, there is no one program suitable for all agencies to follow owing to the wide variety in equipment, operating environment, and available resources. Despite the differences, five steps were identified through this study that could assist agencies in implementing a more effective PM program: 1. Monitor and Benchmark both Scheduled and Unscheduled Maintenance—A monitoring system that distinguishes between scheduled maintenance activities versus those made as reactive measures to address unexpected failures establishes a benchmark for PM performance. 2. Establish Foundation PM Intervals and Related Activities—An effective PM program is one that first satisfies regulatory requirements and manufacturers’ specifications. Integrating more thorough driver and service line inspections into the overall PM pro- gram makes it more comprehensive and effective at reducing in-service mechanical breakdowns. 3. Consider Local Operating Conditions and Experiences—Once foundation PM inter- vals and related activities have been established they can be modified by analyzing the causes of unscheduled maintenance and accounting for local conditions and experiences. 4. Implement a QA Program—Successful PM programs depend on the quality of work done by those operators, technicians, and service line personnel who carry them out. A QA oversight function verifies that PM inspections and repairs have been done thoroughly and correctly. 5. Data Analysis and Program Refinement—PM constantly evolves. Improvement is a continuous cycle of monitoring unscheduled maintenance events, analyzing the infor- mation generated from the data to determine root causes, and fine tuning the PM pro- gram by altering intervals, adding new maintenance procedures, or both to reduce the number of unscheduled events. Findings from this synthesis suggest four areas of future study: 1. Standard procurement language that directs OEMs to group PM schedules and activ- ities for all bus-related equipment into one convenient location. 2. An industry-sponsored peer review program that assesses fleet conditions in terms of the number of per-bus defects and safety violations, examines records to deter- mine adherence to PM policy, and assists agencies in establishing more effective PM programs. 3. Determine staffing level requirements for maintenance personnel including the num- ber of technicians needed to carry out PM activities based on fleet size, fleet makeup, level of advanced technology, operating conditions and environment, and other factors. 4. Examine how maintenance data could be analyzed to assist maintenance managers in establishing more cost-effective PM intervals and related repair activities. 3