Although specialized equipment and vehicles make up a large portion of state transportation budgets, an OTREC research report found little consistency in how states decide to replace this equipment.
Researchers David Kim and David Porter of Oregon State University surveyed 25 state departments of transportation to determine how they made replacement decisions. Nearly all consider the age of the vehicle or piece of equipment, with many considering how much use it gets.
Around half use thresholds, such as number of miles or months in service, to identify candidates for replacement. Some consider the equipment’s repair cost or operating cost, while others rely on physical inspections. None explicitly considers greenhouse gas emissions or other environmental concerns in its replacement criteria.
Given the huge range of approaches, Kim and Porter wondered if modeling could lead to better decision-making. They ran various models against the simple approach of using equipment age as a threshold value.
As it turns out, the simple approach isn’t too bad. In fact, it does better than one complicated mathematical model and about the same as a second model.
That may...Read more