By Tim Rydholm, Washington State Department of Transportation
You just have received an email from your agency’s Asset Management Office. They have been told their asset management documentation is way too complex and now each asset management group must come up with one sentence per type of asset that describes the scope and resources it takes to manage it. Moreover, it’s a fill-in-the-blank sentence:
Our agency has (x number) of (asset y) worth ($z dollars) and requiring $(a dollars) per year to preserve.
Your task is to fill-in-the-blanks for pavements at your agency.
For the Washington State DOT (WSDOT) pavements, this is how blanks would be filled in: WSDOT has around 18,500 lane miles of pavement worth $16 billion and requiring $250 million per year to preserve. This information is contained in the most recent December edition of WSDOT’s Gray Notebook.
As a pavement asset manager, you probably have some follow up questions. Does the lane mile total include ramps? No. Does WSDOT manage county roads? No, unlike some states, county and city roads are managed locally. What is the Annual Vehicle Miles Traveled (AVMT) for these pavements? In 2014, it was 32.17 billion. What’s included in the costs? At WSDOT we include all project costs including traffic control and engineering. Was depreciation or the value of the right of way used in estimating pavement worth? No. The $16B value only includes the replacement (reconstruction) of the pavement in like-kind and excludes bridges, land value, lighting and guardrails.
And the most complex follow up question – how was $250 million calculated as the annual amount needed to preserve the pavement system? The level of complexity going into this type of analysis may vary. In this case, a “back of the napkin” type of calculation is sufficient (at least as a starting point). For WSDOT, pavements can be divided into 3 broad categories: Low to Medium Traffic, Medium to High Traffic, and High Traffic/Special Circumstance. Each of these categories lends itself to a specific preservation strategy: Chip Seal resurfacing, Asphalt resurfacing and Concrete, respectively. Using average cost and life information, the back-of-the-napkin calculation can be done:
| Asphalt | Chip Seal | Concrete | |
| Avg. Life | 16 Years | 8 Years | 50 Years |
| Avg. Cost per Lane Mile | $200,000 | $40,000 | $2,500,000 |
| Applicable Lane Miles | 9,250 | 7,250 | 2,000 |
| Avg. Annual Cost | $115 M | $35 M | $100 M |
| Total Annual Cost: $250 M | |||
The numbers in the above table are rough averages that have been specifically rounded to make a “neat” number for communication. Our Pavement Management Office has done several more in-depth analyses for network lowest life cycle cost that produce ranges of average annual need between $225 M and $275 M, but for the purposes of communication and planning $250 million is very useful as the benchmark for sufficient funding for pavement preservation.
I think a lot can be learned just by completing this fill-in-the-blank exercise. Can you fill in the blanks for your agency? Are you willing to share in the comments? Do you have other questions or considerations that may go into such an answer – or can you think of a better sentence that describes the scope and cost of your pavement assets?
For more information, please contact Tim Rydholm at: rydholt@wsdot.wa.gov