Asphalt surfaces have a typical service life of 8 to 12 years, depending on traffic and weather conditions. Asphalt resurfacing is necessary when the asphalt surface has reached the end of its service life or if other methods of restoration cannot repair the roadway. A new asphalt surface will improve driving conditions as well as the aesthetics of the roadway. Asphalt resurfacing is a multi-step process that usually involves several work crews, accompanied by proper construction signs and work-zone traffic control measures to maintain public safety.

Resurfacing an asphalt roadway requires the following steps:

• Adjustment (lowering) of utilities to allow milling machines to traverse the roadway without damaging utility assets.
• Removal (milling) of old surface using a milling machine. All milled surfaces must be cleaned by the milling contractor and marked appropriately to safely direct traffic. (Milling may not be required on streets with no curb and gutter; however, the edges of streets with no curb and gutter may be trimmed prior to milling in order to provide a more uniform milled surface.)
• Re-adjustment (raising) of utilities so that they will again be flush with the new surface that will be applied.
• Application of a tack coat to milled surface to serve as a binder for the new surface that will be applied.
• Application of new paving surface by paving machines.
• Application of new thermal plastic pavement markings on new pavement surface.

Surface treatments are applied as preventive maintenance to replenish lighter oils and rejuvenate the roadway in order to prolong its service life. Metro uses pavement condition data to analyze and determine where and when surface treatments are to be applied. Because the cost of applying surface treatments is minimal compared to resurfacing the roadway, Metro makes an effort to utilize surface treatments to extend the service life of streets throughout Davidson County.

Surface Treatment Process includes following steps:

• Before surface treatment can be applied, the roadway must be cleaned. A power broom is used to clean the roadway surface.
• The surface treatment will be applied from a distributor truck.
• Workers will manually spray corners and hard to reach areas.
• The street will be covered with a layer of sand for approximately 24 hours while the surface treatment cures.
• The sand will be swept by the contractor.

Over time, sunlight oxidizes the oils in asphalt, causing the asphalt to become brittle and develop cracks. Cracks in asphalt roadways provide a place for moisture to reach the pavement base and will ultimately lead to more extensive deterioration. Crack sealing is a maintenance method to repair construction joints, and longitudinal cracks in the roadway.  Crack sealing is necessary to prevent water from entering the base of the roadway, which could require major reconstruction.

The Crack Sealing Process includes the following steps:

• The cracks in the roadway may be cut out to a specified depth.
• The workers will clean and dry the open roadway cracks with high-pressure air and heat.
• A hot-pour crack sealant will be applied.
• Sand will be placed over the sealant to reduce stickiness.