jan-2018

38 39 that for everything. So, now,Medford PublicWorks operates on what we call the ‘lowest life-cycle cost approach.’” As an example, Crebbin recounts that, formerly, the department’s road maintenance program, con- sisting of asphalt overlays,wasn’t keeping up with the demand.“So,we decided to take a lowest life-cy- cle cost approach and actuallymeasure the condi- tion of all the pavements to decide what’s optimal for the system, so over the life of the transportation system,we’ll spend the least amount of money. We found a company that has a machine called a laser road surface tester.They drive over the streets, and check the roughness and the deflection in the cracking with video and laser and microwaves. They come back every couple of years and drive our streets again, so we can see exactly how fast they’re deteriorating and, based on their score,we can de- termine what might be the appropriate treatment.” The outcome of the department’s efforts to save money over time resulted in a completely revamped maintenance program, based on the Federal High- MEDFORD, OREGON wayAdministration’s Life-Cycle Cost Analysis in Pavement Design.“We don’t just do overlays, any- more,”Crebbin says.“Nowwe do a fog seal,which I call ‘sun screen for streets,’ because as asphalt absorbs sunlight, it gets cross-linked and that’s what makes it brittle and crack.The fog seal that we spray on rejuvenates it and keeps it flexible longer. “And that delays the next stage of maintenance, which is a slurry seal. It’s like zinc oxide for a street. You put a very thin slurrymixture over the top of the street,which starts blocking the oxidizing rays, and you can limit cracking; you can seal up the cracks to keep the water out.And then the next step,which we just started doing this year, is a chip seal,which is some gravel in a slurry seal type application. “So,we are delaying having to do overlays proba- bly anywhere from 15 to 20 years,which costs mon- ey upfront, because you have to do this additional maintenance, but you save waymore money later, so you’re coming out significantly ahead.” Another project in which Crebbin’s department applied the lowest life-cycle cost approach con-