Now more than ever, fleet assessments are smart business because transit agencies are asked to do more with less and budget constraints force agencies to run cars well past their 30-year design life. An undiagnosed fleet-wide component failure on an aging vehicle can singlehandedly cripple a transportation system, but a midlife assessment is a process that can detect problems before they become crises.
Over the past decade, total capital investments in light rail systems have nearly doubled, but new vehicle procurement expenditures have remained flat. As a result, transit agencies are being forced to support their new infrastructure investments with a combination of new and aging rolling stock, ultimately resulting in a doubling of vehicle maintenance costs over the same decade.
Predicting the ability of a vehicle fleet to operate to its expected life expectancy and beyond requires inspection of critical vehicle components and systems. A thorough fleet assessment provides the data needed to determine the remaining life of vehicle components. This, in turn, will clarify whether overhaul is worth the investment, or if new cars are the better choice. These 5 steps form the basis of an assessment:
Typical Steps in a Fleet Assessment
1. Gather Information
First, evaluate reliability data, maintenance logs and vehicle documentation to identify potential problems. Next, consult the maintenance staff to discuss troublesome systems and fleet-wide problems, as these are often symptoms of greater issues.
2. Perform Inspections and Tests
Begin the inspections with an evaluation of the vehicles’ most critical areas: structure and electrical systems. These critical systems are the most likely to influence life extension decisions because of their cost and impact on vehicle operation.
Carbody and truck structures are typically susceptible to fatigue cracking and corrosion damage. Expert fractography can be used to investigate the cause of cracks that are found during inspection. Additionally, dynamic in-service testing, in which strain, acceleration and displacement of key structural and suspension elements are measured will indicate the forces and stresses experienced by the vehicle while in service. Due to budgetary and other practical limitations, the number and location of strain gages applied must be carefully considered. It is important to enlist the help of experienced analysts to properly predict fatigue-prone areas. The results of the dynamic testing will be compared with mechanical properties of components and weld classifications to predict remaining service life of the carbody and truck structures.
In parallel with the structural evaluation, review the major electrical power, passenger comfort, system safety, and control systems. Vehicle control and communications systems demand special attention, as they are safety-critical and are heavily dependent on often obsolete electronics and software. Systems integration is another area of focus, especially when considering the retrofit of legacy systems with modern technologies. Examples include installation of new systems such as communications-based train control (CBTC) and closed circuit TV (CCTV), as well as retrofitting controls for propulsion, brake, and door systems.
3. Summarize Findings
The results of the information gathering and inspection efforts are summarized into a report. The report must present the results of the assessment in a clear and concise manner that will easily be understood by both technical and non-technical members of the management team.
4. Conduct Financial Analyses
Once completed, the fleet assessment will serve as a valuable investment analysis tool to make critical repair-or-replace decisions. By documenting fleet condition, establishing the likely end of service life, and highlighting areas that will require capital investment to reach the service life goal, an agency can make informed choices. The resulting data feeds the financial analysis to compare the cost of overhaul versus the cost of buying new.
5. Purchase New or Overhaul
In some cases, vehicles will have reached a severe level of deterioration or obsolescence, and it makes more sense to buy new vehicles rather than further invest in failing equipment. A normal procurement becomes the next step. If, however, the financial analysis indicates that overhaul is best for the existing fleet, then the next step is to generate a detailed overhaul. Any components determined to have a predicted life less than the service life goal will be incorporated into a systematic plan to renew the fleet.
A fleet assessment should be conducted on every vehicle type when it reaches its midlife. The assessment will help to identify hidden issues with the vehicles, increase efficiency and reliability, and allow agency planning efforts to proceed with confidence. A fleet assessment led by experts can help agencies extend their fleets’ lifespans and provide significant cost savings versus new car procurement. Even if the fleet assessment leads to the conclusion that overhaul is not advisable, the agency will still have gained a realistic timeline to use for planning a new car procurement and solid financial data to support the recommendation.
Daniel Lang, P.E., is an engineer with LTK Engineering Services.
