Preventive Maintenance Intervals for Transit Buses (2010)

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7INTRODUCTION This first portion of this chapter summarizes findings from a literature review of PM programs. The second provides a general overview of PM classifications, which also serves to review the overall subject. LITERATURE REVIEW Findings from the literature review are grouped under vari- ous PM definitions found, inspection regulations established by the U.S.DOT, PM portions of a comprehensive study writ- ten specifically for buses, and five essential steps to PM as adopted from the trucking industry. Preventive Maintenance Definitions Although PM definitions are expressed differently, the liter- ature search revealed that the intent is very similar. Weibull, a noted resource for predicting component reliability, defines PM as a schedule of planned maintenance aimed at the pre- vention of breakdowns and failures (2). The definition con- tinues by stating: The primary goal of PM is to prevent the failure of equipment before it actually occurs. It is designed to preserve and enhance equipment reliability by replacing worn components before they actually fail . . . Recent technological advances in tools for inspection and diagnosis have enabled even more accurate and effective equipment maintenance. The ideal PM program would prevent all equipment failure before it occurs. The Department of Defense defines PM as: The care and servicing by personnel for the purpose of maintain- ing equipment in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects (3). A study entitled Bus Fleet Management Techniques Guide, reviewed in greater detail here, provides a similar definition: Preventive maintenance is carried out at predetermined inspection intervals, typically based on accumulated mileage, or other pre- scribed criteria, such as when a monitored condition exceeds a tolerance level. This type of maintenance is intended to reduce the likelihood of the in-service failure of components by anticipat- ing their failures . . . As preventive maintenance is increased, the amount of emergency repairs should decline, thereby increasing the efficiency of the maintenance operation and resulting in better control of costs (4). John Dolce in his book Fleet Management expresses a similar definition with a focus on PM inspections: Preventive maintenance inspection . . . is a systematic servic- ing and inspection of motor vehicles and equipment on a pre- determined interval based on time, mileage, engine hours, or gallons of fuel used. The interval varies with the type of equip- ment and the use to which it is assigned (5). As the various definitions imply, equipment and man- power considerations are critical. However, the most impor- tant tenet of PM is to ensure customer satisfaction by present- ing buses that are safe to passengers, preserve taxpayer investment, and are capable of delivering on-time service without mechanical interruptions. Effective PM also allows buses to reach their useful service life as defined by the FTA. Department of Transportation Regulations The literature search also revealed a series of U.S.DOT regu- lations. Local and state governments typically have similar requirements; agencies are urged to seek out and become familiar with all legal aspects of vehicle inspection and repair. Code of Federal Regulations Title 49 The U.S.DOT has several publications that pertain to vehi- cle inspections. Primary department of transportation (DOT) requirements reside in the U.S. Code of Federal Regula- tions (CFR), Title 49, which applies specifically to trans- portation. Of special interest is CFR 49 Chapter Three, which contains regulations established by the FMCSA, a division within the U.S.DOT (6). The government agency is charged with reducing crashes, injuries, and fatalities involv- ing large trucks and buses. In addition to enforcing commer- cial driver’s license (CDL) requirements and the transportation of hazardous materials, FMCSA issues and enforces a host of regulations affecting vehicle safety, including periodic inspections. While FMCSA regulations apply to commercial trucks and buses, many transit agencies use them as a guide- line for their own maintenance operations. CHAPTER TWO LITERATURE REVIEW AND PREVENTIVE MAINTENANCE CLASSIFICATIONS

CFR 49 Part 396 FMCSA’s Vehicle-Related Regulations, CFR 49 Part 396, specifically addresses inspection, repair, and maintenance. Table 2 lists various subparts of Section 396. Guidance on some regulations is provided by the FMCSA, indicated by “Yes” in the last column of Table 2. Summary guidance information is provided here; complete information is found at http://www.fmcsa.dot.gov. Appendix C summarizes interesting sections of CFR 49 Part 396 in greater detail. Of particular interest is Section 396.5, Inspection, Repair and Maintenance, which requires push-out windows, emergency doors, and emergency door marking lights to be inspected every 90 days at minimum, and maintain records showing compliance. Technicians must be qualified to carry out vehicle and brake inspections (Parts 396.19 and 396.25). Minimum criteria needed for passing vehicle inspections are also listed (Appendix G of Part 396). Again, transit agencies may want to review these commercial vehicle requirements and adapt them for their own use. CFR 49 Part 393 Another essential DOT requirement is CFR 49 Part 393, Parts and Accessories Necessary for Safe Operation. Although most are directed at manufacturers to ensure compliance with Federal Motor Vehicle Safety Standards (FMVSS), the end user is responsible for ensuring that parts remain in place, are operational, and continue to comply with requirements when replaced. CFR 49 Part 37 Under 49 CFR Part 37, Americans with Disabilities Act (ADA), “Transportation Services for Individuals with Dis- 8 abilities,” transit agencies are required to have a system of regular and frequent maintenance checks for wheelchair lifts, ramps, and other required equipment on non-rail vehicles that is sufficient to ensure that the lifts are operative. Although ADA does not prescribe how wheelchair lifts and other required accessibility equipment are to be maintained, Sec- tion 37.163 states that “the point of a preventive maintenance program is to . . . catch broken lifts as soon as possible, so that they can be repaired promptly” (7). Responsibility for assuring accessibility equipment relia- bility becomes a collaborative effort between bus operators and maintenance personnel. Although there is no specific requirement for daily cycling of lifts or ramps, many agen- cies require operators to perform this practice before beginning service (see Operator Inspections on page 11). Operators are, however, formally required to immediately report lift failures, while maintenance personnel must promptly make repairs. Agencies are in violation of ADA if they fail to check lifts regularly and frequently, or they exhibit a pattern of lift breakdowns in service. Additional information regarding ADA maintenance requirements can be found at http://www.fta.dot.gov/civilrights/ada/ civil_rights. Satisfying Inspector Requirements Through Automotive Service Excellence Certification One way to ensure that technicians meet applicable regula- tory requirements is through the Automotive Service Excel- lence (ASE) Transit Bus Maintenance Certification Program. The ASE program, previously available only for automobile and truck technicians, has been expanded to include buses. The program, which is completely voluntary, was made possible by TRB through TCRP. Part Regulation Guidance 396.1 Scope 396.3 Inspection, repair, and maintenance Yes 396.5 Lubrication 396.7 Unsafe operations forbidden 396.9 Inspection of motor vehicles in operation Yes 396.11 Driver vehicle inspection report(s) Yes 396.13 Driver inspection Yes 396.15 Drive-away and tow-away operations and inspections 396.17 Periodic inspection Yes 396.19 Inspector qualifications Yes 396.21 Periodic inspection recordkeeping requirements Yes 396.23 Equivalent to periodic inspection Yes 396.25 Qualifications of brake inspectors Yes Appendix G Note: Applies to commercial trucks and buses. Minimum Periodic Inspection Standards Yes TABLE 2 FMCSA VEHICLE-RELATED REGULATIONS, PART 396

9ASE certification provides an objective measurement of mechanical and electrical competency in ten specific bus areas. Several tests, including those for bus brakes and electrical/electronics, have already been developed. One pertaining to preventive maintenance inspections (PMIs), referred to as Test H8, is also now available. Additional information and study guides can be obtained from ASE at http://www.ase.com. Information on the ASE program is available from TRB at http://www.trb.org. Bus Fleet Management Techniques Guide Although written in 1985, Bus Fleet Management Techniques Guide, Maze et al. (4) offers useful insight and information regarding PM as it applies to transit buses. The Guide addresses three basic areas: 1. Statistical analysis of component and part failure mile- ages for maintenance planning, 2. Life-cycle economic analysis for component and bus replacement and decision making, and 3. Nontechnical methodologies for maintenance manage- ment information systems. Optimum Component PM Of interest to this study is information regarding the optimum level of PM for each part or component, which according to the Guide depends on five factors: 1. Component Failure Patterns, classified as “age- dependent,” such as brake shoes, and “age-independent” such as fuses. Preventive replacement is only appro- priate for components that exhibit age-dependent patterns. 2. Repair Costs. If it costs just as much to repair an item before it fails as it does after it fails, then the item should be replaced after it fails, except where failure of the part in question can cause collateral damage or result in ser- vice interruption. 3. Vehicle Spare Ratio. The flexibility to schedule preven- tive component replacements is a function of the number of spare buses available. 4. Ability to Monitor Component Condition. PM can be performed when a condition check indicates that the component is wearing out. Brake shoe inspections are a common example. 5. Safety implications. In cases where safety is involved (i.e., brakes), safety rather than cost minimization should dictate preventive and corrective maintenance levels. Predicting Component Failure The Guide devotes several chapters to Weibull Distribution Failure Analysis, which uses a scientific approach to deter- mine intervals for replacing parts and components. As noted in chapter three of this study, the Weibull analysis allows managers to predict component life by monitoring life data from a representative sample of vehicles. Since publication of the Guide, computer programs have been developed that more easily make the needed calculations. One such applica- tion used by Dallas Area Rapid Transit (DART) is described in chapter three of this study. Four Approaches to Component Maintenance The Guide describes that part or component maintenance can be accomplished in four ways: 1. Condition-Based Maintenance, where monitoring and inspections are used to determine replacement inter- vals. Brake shoe wear and oil consumption are two examples. 2. Fixed-Mileage Maintenance, where maintenance actions are carried out at regular mileage intervals such as engine oil and filter changes. 3. Operate-Until-Failure Maintenance, where all mainte- nance actions are corrective in nature. This is done as a default in cases where parts are not being monitored or when it is more cost-effective to replace a part after failure because there are no safety or service interrup- tion implications. 4. Design-Out-Maintenance, where the maintenance prob- lem is removed through redesign. An example given is where the location of the air conditioning system in advanced design buses of the early 1980s was moved into a separate compartment above the engine. Life-Cycle Costing The Guide also discusses the applications of life-cycle cost- ing (LCC), where PM is identified as a significant cost driver. Although most of the discussion applies to the overall vehicle procurement, similar LCC principals presented in the Guide can be applied to individual bus parts and components. Additional information regarding LCC is presented in a TRB paper by Hide et al. (8). Detailed and accurate monitor- ing of vehicle operating costs on a component basis is essen- tial to determining lifetime performance of individual vehicle types. Research conducted by the authors identified 12 months as the most satisfactory period over which to aggregate vehi- cle operating costs. A comprehensive LCC system provides management with the ability to monitor current cost trends, predict future costs, and assess the implications of different policy decisions. According to the study, benefits of an LCC system have been demonstrated to be the equivalent of renew- ing 1.5% of the vehicle fleet annually at no additional cost, while at the same time improving vehicle availability.

Five Steps to Effective Preventive Maintenance In the article “Five Steps to Improving a Government Fleet Preventive Maintenance Program,” Robert Johnson, with the National Truck Equipment Association, offers a sensi- ble approach to optimizing PM programs (9). Elements of that approach have been modified based on the literature review and survey responses to make them more comprehensive and applicable to bus transit. 1. Monitor and Benchmark both Scheduled and Unsched- uled Maintenance—The effectiveness of a PM action or program cannot be evaluated unless scheduled and unscheduled maintenance events are accurately tracked by bus type (year, make, model, etc.) and major bus components (engine, transmission, axles, etc.). Moni- toring provides a benchmark to gauge whether modifi- cations made to the PM program are indeed producing fewer service interruptions. Adding detail about each repair will greatly assist with failure analysis. 2. Establish Foundation PM Intervals and Related Activities—Essential elements of PM include daily operator and service line inspections and periodic PMIs. Bus operator inspection requirements are spec- ified in DOT regulations. However, agencies can also provide basic technical training to bus operators and work with them in a team setting to make their inspec- tions integral to the overall PM program. Likewise, daily service line inspections can be enhanced with addi- tional activities and by making greater use of electronic onboard monitoring and reporting systems. When it comes to scheduling PM, the most efficient scenario according to Johnson is one where activities are grouped and the number of intervals or “touches” is minimized. The process begins by fully understand- ing PM requirements established by original equip- ment manufacturers (OEMs), as well as safety inspec- tion requirements established by federal and local authorities. 3. Consider Local Operating Conditions and Experiences— Once foundation intervals and activities have been established to satisfy OEM and regulatory require- ments, Johnson recommends adding other preventive steps. Included are those that address local operating conditions and take into account experiences gained through the agency’s monitoring program and fault analysis. Modifications to foundation intervals must conform to regulatory requirements. Actions taken outside OEM specifications may violate warranty coverage and are best done in consultation with them. 4. Implement a Quality Assurance Program—A PM program is only as good as the operators, service line personnel, and technicians carrying out the work. To ensure PM activities are done correctly, a QA program is vital. In cases where technicians performing inspec- tions are also required to make any needed repairs, there may be a tendency to overlook certain defects to 10 avoid the work involved. In other cases personnel may lack experience and the ability to properly identify defects. Given the importance of PM and related safety implications, all tasks—inspection and subsequent repairs—must be done correctly. This could be veri- fied by random spot checks performed by dedicated QA personnel or by maintenance supervisors and lead technicians. Any deficient work identified should then be used as an opportunity to retrain staff. 5. Data Analysis and Program Refinement—Examine incidents that take place between planned mainte- nance events, look for trends and causes of failures, and take corrective action by adjusting scheduled PM activities and intervals accordingly. Needed actions resulting from analyses should be included on PM checklists and work orders for technicians to follow. These instructions require constant updating and should be unique to each bus and equipment type. Regardless of how well conceived and executed, a PM program is constantly evolving based on new data and changing technology, conditions and service demands, and fleet retrofits and acquisitions. Some PM actions are put in place to address new propulsion tech- nologies. Others are seasonal, temporary, or directed at specific fleets such as aging buses that typically need more attention. A PM program must evolve over time to be effective. Monitoring systems that distinguish between scheduled and unscheduled maintenance will help determine if changes made to the PM program are yielding desired results. PREVENTIVE MAINTENANCE CLASSIFICATIONS PM can be classified in various ways. For this study, it is broken down into three fundamental elements: 1. Inspections; 2. Repairs, campaigns, and replacements; and 3. Overhauls/refurbish. Basic information provided here is also intended as a general overview of PM. Chapters three and four detail measures taken by survey responders in carrying out specific PM activities. Inspections Inspections are the most common form of PM and typically consist of three separate and distinct functions: 1. Service line inspections, 2. Operator inspections, and 3. PMIs. Service Line Inspections Service line inspections are generally done daily as buses get refueled and cleaned. The purpose is to check vital fluid

11 levels, examine tires for excessive wear and adequate air pressure, visually check for body and other damage, and to obtain as much information as possible about the well being of major bus systems. How service line inspections are con- ducted depends on the level of automation. With a manual approach, inspections are done with little or no electronic assistance. Although vital and necessary, the method is limited because personnel performing these duties (referred to as cleaners or hostlers) generally lack technical experience. Manual inspection procedures usually consist of “bumping” the tires with a rod or stick, listening for a partic- ular sound that indicates low tire pressure; manually check- ing engine oil, transmission fluid, and coolant levels; visu- ally checking the engine compartment for leaks, listening for unusual sounds and other abnormalities; and walking around the bus to note inoperative lights and body damage. Hostlers also enter fuel and fluid consumption data and note any inspection irregularities before taking buses through the washer and back to parking locations. Driving to and from the service line also serves as a road test of sorts. Manual service line functions are gradually being replaced by more sophisticated electronic systems such as the one used by WMATA highlighted in chapter five. The system contin- ually monitors and records onboard functions and transmits abnormalities in real time and automatically downloads data as the bus enters the service line depending on how critical the malfunction is. Advances in electronics, now part of virtually every bus control system, make it much easier to collect onboard data because of the ability to electronically monitor, store, and report abnormalities when prompted (10). Integrated onboard data collection with automatic down- loading is an ideal service line tool in that it relieves hostlers of making many routine daily inspections and provides infor- mation well beyond the abilities of even the most experi- enced technicians. Operator Inspections Bus operators also provide an excellent daily inspection opportunity, especially when assigned to the same bus where they can become more sensitive to abnormal conditions. Operators, depending on agency size, may be legally required to perform pre-trip inspections as part of their CDL require- ment (11). CDL requirements direct operators to inspect: • Engine compartment (engine off) • Engine start and instrument function • Brake systems, including air brakes (if applicable) • Passenger entry and wheelchair lifts and ramps • Emergency exits and related warning devices • Passenger seating • Doors and mirrors • Vehicle is level with no audible air leaks • Fuel tank(s) and fill cap • Exterior compartment doors • Battery box. It would benefit agencies to become thoroughly familiar with CDL pre-trip inspection requirements for their particu- lar operation and integrate the inspections into their overall PM program. Additional information is available at the CDL Digest, http://www.cdldigest.com. As mentioned earlier in this chapter, the ADA requires agencies to have a system for regular and frequent checks, suf- ficient to determine if wheelchair lifts are actually operative. Because ADA requires operators to inform the agency when a lift breaks down in service, many agencies also require bus operators to cycle lifts daily as part of the pre-trip inspection routine to ensure that lifts are indeed operational. An operator inspection card is typically used to docu- ment pre-trip inspection findings along with any other abnormalities that may develop in service. The card is com- pleted and returned daily to the maintenance department for review. Some agencies go a step further by having mainte- nance personnel greet operators returning from service to review noted defects, whereas others provide operators with feedback regarding maintenance actions taken as a result of reported problems. PMIs PMIs are an essential PM element. Buses are brought in at established intervals for various inspections and service work. The intent is to identify and correct problems on a sys- tematic basis before they become more serious. Early detec- tion allows agencies to plan and prioritize repair schedules, order needed parts, and accordingly plan staff allocation. The alternative is addressing failures when they occur in revenue service, resulting in service delays and passenger inconve- niences. In more extreme cases, undetected and neglected equipment defects can lead to injury. In addition to federal, state and local requirements, an essential factor in establishing PMI intervals is the need to change oil and provide other chassis lubrication as specified by the equipment manufacturers. The oil change interval also provides an excellent opportunity to inspect other critical areas and take corrective action based on identified defects. Some agencies separate inspections as a stand-alone function using specially trained technicians who focus only on inspections without being required to perform repairs. A critical aspect of conducting PMIs is to determine when identified defects get repaired. Understanding that it may not be possible from a time and parts availability standpoint to immediately correct all noted defects, some type of priority system is warranted. Some agencies assemble a list of those defects that must be corrected before a bus is allowed back into service. Safety-critical defects based on federal and local

regulations are typically on this list, along with other defects that affect component life. All other noted defects are either rescheduled or left to the next PMI. Repairs, Campaigns, and Parts Replacements Repairs After defects are identified as part of the inspection process they require repair. Allowing defects to exist over time defies the purpose of PM. When technicians and drivers continually notice the same defects on buses they have a tendency to accept them as the norm. Implementation of a defect classification system that clearly identifies safety and other critical defects is one way to prior- itize when defects get repaired. Regardless of the approach used, defects identified during a PMI should be repaired either before the bus resumes revenue service or at the next scheduled PMI. Allowing defects to accumulate causes the fleet to deteriorate over time. QA measures such as those described in chapter four can help ensure that defects are properly identified and repaired. Another approach is to hire an outside inspection firm to con- duct a fleet audit on a periodic basis, where defects are item- ized on a percentage of buses to obtain an objective assess- ment of fleet condition. An alternative is to have the industry create a peer review of maintenance experts to conduct peri- odic reviews. Campaigns Campaigns or retrofits are scheduled repairs that take place on an entire series of equipment or buses made in response to a common problem. As an example, a new bushing found effective at preventing doors from coming out of adjustment is installed on all buses using that bushing type. The whole- sale replacement, which can be scheduled as part of a regu- larly scheduled PMI or separately, is taken as a preventive measure to improve safety and reliability, and reduce road calls and other unscheduled events. 12 Replacements Another PM repair activity involves replacing parts and com- ponents before they fail. In a perfect world the life cycle of key parts and components would be calculated from a database of agency information and replacements made at the optimal interval. In reality, the ability to estimate equipment life is a dif- ficult task (12). Many variables make it hard to predict with accuracy when a vehicle component or part will fail. Vari- ables include corrosion, manufacturing inconsistencies, mater- ial fatigue, and whether loading on the component is static, cyclic, or dynamic. These factors combined with the inability to establish an effective database of historical operating condi- tions such as operating pressure, temperature, and vibration fur- ther complicate life-cycle estimates. Despite these variables, mathematical models have been developed to predict equipment life. The models are routinely used in aerospace and military applications, where conse- quences of failure are more severe and resources more plenti- ful. Chapter three provides more detail and examples of various tools available to make such predictions. Overhauls/Refurbish Certain equipment is completely refurbished or overhauled on a periodic basis as a preventive measure. This typically occurs on larger, more expensive items such as entire bus over- hauls, typically done at mid-life, and large components such as engines, transmissions, and axles. Other such components include fareboxes, radios, starters, alternators, and brake sys- tem components. As with the replacement of individual parts, overhauls are ideally done at the end of the life cycle to pre- vent more serious and costly problems. Overhauls also provide an opportunity to upgrade com- ponents to later technology. For example, when engines reach the end of their life cycle they can be upgraded with redesigned parts to extend service life and reduce exhaust emissions. The same applies to other components where longer-lasting brushes are installed in electric motors when refurbished, and where electronic equipment is fitted with improved circuit boards to improve reliability.