The Covid19 pandemic has placed unusual stress on public transit agencies. This stress forces agencies to look again at their processes and equipment.
This blog focuses on bus systems and their practices for spare parts management. However, there are lessons here for other types of public transit, including rail and light rail.
Back in 1995, the Transportation Research Board (TRB) of the National Research Council published a report that still has relevance. System-Specific Spare Bus Ratios: A Synthesis of Transit Practice stated
The purpose of this study was to document and examine the critical site-specific variables that affect the number of spare vehicles that bus systems need to maintain maximum service requirements. … Although transit managers generally acknowledged that right-sizing the fleet actually improves operations and lowers cost, many reported difficulties in achieving and consistently maintaining a 20 percent spare ratio as recommended by FTA… The respondents to the survey advocated that more emphasis be placed on developing improved and innovative bus maintenance techniques, which would assist them in minimizing downtime and improving vehicle availability, ultimately leading to reduced spare vehicles and labor and material costs.
Grossly simplified guidelines like “keep 20% spare buses” are easy to understand and measure but mask more detailed tactics that can provide more tailored policies. If operational reliability can be improved for each bus, then fewer spares are needed.
One way to keep each bus up and running more often is to improve the management of inventories of spare parts. Here is where modern supply chain management can make a significant contribution. The TRB noted this in their report:
Many agencies have been successful in limiting reliance on excess spare vehicles. Those transit officials agree that several factors and initiatives have led to their success and are critical to the success of any program [including] … Effective use of advanced technology to manage critical maintenance functions, including the orderly and timely replacement of parts… Failure to have available parts and other components when they are needed will adversely affect any maintenance program. As long as managers are cognizant of the issues and vigilant about what tools are available to them, the probability of buses [being] ‘out for no stock’ will greatly diminish.”
Effective inventory management requires a balance between “having enough” and “having too much.” What modern software can do is make visible the tradeoff between these two goals so that transit managers can make fact-based decisions about spare parts inventories.
There are enough complications in finding the right balance to require moving beyond simple rules of thumb such as “keep ten days’ worth of demand on hand” or “reorder when you are down to five units in stock.” Factors that drive these decisions include both the average demand for a part, the volatility of that demand, the average replenishment lead time (which can be a problem when the part arrives by slow boat from Germany), the variability in lead time, and several cost factors: holding costs, ordering costs, and shortage costs (e.g., lost fares).
Innovative supply chain analytics uses advanced probabilistic forecasting and stochastic optimization methods to manage these complexities and provide greater parts availability at lower cost. For instance, Minnesota’s Metro Transit documented a 4x increase in return on investment in the first six months of implementing a new system. To read more about how public transit agencies are exploiting innovative supply chain analytics, see:
- Optimizing Parts Management at BC Transit
- Smart Software and Metro Transit
- Smart Software Helps Metro-North Railroad Keep the Trains Running On-Time
Smart Software’s Channel Sales Director and Enterprise Solution Engineer, to present three sessions at this year’s Microsoft Dynamics Community Summit North America event in Orlando, FL.
Smart Software, will lead a 30-minute webinar as part of the WERC Solutions Partner Program. The presentation will focus on how a leading Electric Utility implemented Smart Inventory Planning and Optimization (Smart IP&O) as part of the company’s strategic supply chain optimization (SCO) initiative.
The supply chain has become the blame game for almost any industrial or retail problem. Shortages on lead time variability, bad forecasts, and problems with bad data are facts of life, yet inventory-carrying organizations are often caught by surprise when any of these difficulties arise. So, again, who is to blame for the supply chain chaos? Keep reading this blog and we will try to show you how to prevent product shortages and overstocking.