The City performs an inventory of approximately one third of its residential and collector roadways on a rotational basis each year, along with all of the arterial and collector streets. Thirteen different distress and roughness data are collected. Each distress is measured with three severity levels and five density levels. The roughness is collected using five levels. Other information included: age, location, maintenance history of the roadway, council district, curb shoulder and pavement types and street functional classifications.
Explaining how we pick the streets to resurface is the most difficult part of the City's program to explain. Let's look at a simple example. Imagine you have a network of streets to maintain, and you have a budget of $1,000. Your choices of streets to spend your maintenance budget on are:
- One street that is falling apart which will take $1,000 to restore to good condition.
- Three streets that are in fair condition that will take $300 apiece to restore to good condition.
- Seven streets that are in good shape. If you spend $100 on each of them, they will remain in good condition for the next 10 years.
Being good stewards of your maintenance budget, and having a goal of keeping the most streets in good condition for as long as possible, how do you spend your money? The best answer is to spend $700 on the good streets to prevent them from deteriorating to the fair condition, then spend $300 on one fair-condition street.
Asphalt pavements deteriorate over time like any other product. This deterioration occurs slowly at first, but then begins to accelerate as time wears on, especially if the streets are neglected. With no maintenance or preserving of the streets, the deterioration begins to show with weathering, cracking, potholes, divots and ruts. Asphalt is designed to be a flexible pavement, to move with the loads it carries and with the expansion and contraction from weather changes. As an asphalt pavement ages, the binder becomes more brittle and has less ability to flex and move. However the pavement still moves under the stresses being applied but it no longer has the flexibility it once did and therefore begins to crack. Additionally as the surface begins to age due to the elements and the binder become more brittle the fine aggregate on the surface of the road begins to release leaving a very rough texture.
Preserving an asset versus rehabilitation and reconstruction is certainly not a new idea and neither are many of the techniques that can be used to preserve a roadway. In order to preserve our roads in a good condition we must implore preventative maintenance measures to the road surface much like we protect the exterior of a house. Just as we caulk and paint the exterior of our houses to protect them from the elements, we can do the same to our roads. Techniques such as crack sealing and thin asphaltic layers are the caulk and paint for roads. The intention is to keep our good roads good by applying the right treatment on the right road at the right time.