In the past few years, I have worked on optimization models for different sectors of the Transportation industry that all have one thing in common: the goal always includes minimizing non-revenue trips, either explicitly defined as the objective function or captured as a cost to minimize. A non-revenue trip, sometimes called a ferry or deadhead, is a move to reposition resources at a new location. In a transportation scheduling or routing model, the majority (hopefully) of the moves yield a revenue: a commercial flight delivers paying customers to a destination, the post office delivers postage-paid mail to our homes, a delivery truck drops off the TV a customer purchased. These revenue trips require resources: airplanes, trucks, trains, pilots, drivers, fuel, etc… Non-revenue trips require the same resources but without generating the revenue required to pay for these resources. Regardless of the company and its products or services, unnecessary non-revenue trips are a waste of time, money, and resources.
An objective I have yet to see in any real-world optimization model I have worked on or encountered is to minimize the impact on the environment. That may be a little surprising since corporations are more focused on going green and helping the environment now than ever before. Recycling is common-place and my mother’s company even provides reduced fare for employees willing to take the bus to work rather than drive their own cars. While I am certain it is possible to include green objectives in a model, I haven’t had a client say “Minimize my emissions or my carbon footprint“. Or have I?
After all, an unnecessary non-revenue trip wastes more than time and money; most modes of transportation require non-renewable fossil fuels and produce emissions that are harmful to the environment. I do want to distinguish between unnecessary and necessary non-revenue trips. It’s generally impossible to eliminate non-revenue trips completely — sometimes a resource is needed in a location where none already exist. But often an optimization model can find ways to sequence stops to reduce the total number of non-revenue trips and minimize the distance of remaining non-revenue trips. Even just reducing non-revenue miles can save fuel and reduce emissions while saving the company money and time. Companies don’t need to explicitly model “green” objectives to help the environment.
Companies that utilize optimization to improve the efficiency of their operations should take an additional step and try to track the overall reduction in non-revenue trips and miles, and other areas of resource waste, as part of their effort to go green and become more environmentally friendly. A carbon footprint calculator like the one at Carbon Footprint can even help a company calculate the reduction in their carbon footprint as a direct result of their optimization efforts. Whether directly modeled in the objective or a by-product of other goals, companies can have a positive impact on the environment through the use of optimization and that benefits everyone.
This blog post is a contribution to INFORMS’ monthly blog challenge. INFORMS will summarize the participating blogs at the end of the month.