In 2016, two professors from Iowa State University embarked on a study to determine the optimal fleet life for Iowa Department of Transportation (Iowa DOT) snowplows. After analyzing 10 years of maintenance records for about 900 single- and tandem-axle Iowa DOT snowplows, the researchers determined six to seven years as the optimal replacement cycle.

Putting the Plan in Place

Two years later, the Iowa DOT has begun working toward reducing snowplow lifecycles from about 17 years to 12 years. And while the fleet hasn’t quite reached the recommended replacement window of six to seven years, Fleet Manager David May said it’s a step in the right direction. 

“Reducing from 17 to 12 years is a big step and required us to ask for additional money from our legislature,” he said. “Our plan is to monitor progress toward our efficiency goals and to review the ‘optimal fleet life’ of our trucks moving forward. If the model continues to point toward a shorter life span, we will take additional steps to move in that direction. We will need a couple years of data before we will see if a shorter life span is still supported by the fleet life optimization model.”

Currently, the fleet is replacing 143 of its 903 plow trucks — approximately double the number typically purchased in a year, and the largest buy for the fleet to date. This initial influx of new plows will move the needle toward lowering the average truck age. Then, starting in FY-2020, Iowa DOT will order 75 trucks per year to phase in the new replacement plan at a more metered cadence over the next 12 years. 

“While we made an initial push for funding for a large quantity of new trucks, phasing this in over a 12-year period will avoid creating peaks and valleys in future funding needs,” May explained. “Replacing a larger quantity will simply create a problem 12 years down the road when a large number of trucks will need replacement all at once. A phased-in approach is the best way to make a change in fleet life.”   

The Benefits of Shorter Lifecycles

So far opting to replace aging plows has helped avoid exorbitant repair costs. “The last winter was hard on our old trucks,” May said. “I was able to make the decision to retire a number of units rather than to commit to expensive repairs on trucks that were near the end of their life. It was a great benefit to avoid costly and time-consuming repairs.”

May said Iowa DOT has already experienced a savings of around $300,000 by not replacing engines in old trucks toward the end of last winter since new trucks are on the way.

This upcoming winter, May said taking delivery of the new trucks is expected to result in increased uptime for the fleet and improved service levels, too. But those aren’t the only upsides of the new replacement schedule. 

“Shortening the lifecycles is a great benefit for our fleet,” May said. “It allows us to adopt improved safety features, increases reliability, and moves us into a fleet that is much more environmentally responsible.”

Analysis Continues

Moving forward, May plans to continue to monitor the results of shorter lifecycles for Iowa DOT snowplows. Although the study focused on snow trucks because they represent the fleet’s single largest investment, May said he is also interested in learning if lifecycles for other types of equipment should be adjusted — whether that’s longer or shorter. 

As the fleet begins to implement the changes as a result of the study, May underscores the value of partnering with Iowa State and investing in research. 

“The project was funded by special research dollars that resulted in a change in our business practice, and we will save money as a result,” May said. “This project shows how strong partnerships, well-invested research dollars, and a lot of work can pay off for years to come. I am proud to have been a part of this change in our fleet.”