Not only is the initial cost of your asphalt paving project less than a portland cement concrete project, but the long term costs of maintenance and eventual rehabilitation are less too.  Paving and traffic return occurs in a matter of hours, rather than days or weeks.  The user-delay costs associated with the shorter work time means a tremendous savings for the traveling public and shipping businesses.  Researchers have found that bumpy roads cost drivers considerably more in vehicle repair costs—in one study fuel costs were 4.5% higher; your smooth, asphalt paving project can reduce these costs, too.

You have many options for your asphalt paving project.  Not only is your pavement flexible, but your options are too.

• Using staged construction, you can build your pavement structure over time, as your funds allow and as traffic loading increases.  Beginning with a good, stabilized base, you can add asphalt layers as needed.
• Your paving project can be done at night or other off-peak traffic times, with minimal disruption to traffic.
• On existing roads in need of maintenance, you can add more layers, or mill off some of the aged pavement and replace it with new asphalt (mill and fill) to keep the same elevation.  This is especially important where there are curbs or for clearances under bridges and overpasses.
• You can even recycle your aged, cracked asphalt road in-place.
• Asphalt paving is ideal for streets, highways, pathways, parking lots, industrial sites, recreational trails, agricultural uses and even
  corrective and preventive maintenance on concrete (PCC) pavements.

• By using a planned sequence of low cost preventive maintenance treatments, your asphalt paving project can be a pavement that lasts for many, many years.

Your asphalt paving project will be smoother than other alternatives—it won’t have the ka-thump, ka-thump, ka-thump of jointed pavements.  It will be more skid resistant (higher friction number) because it uses hard, durable aggregates.  With good drainage and a good mix, your asphalt paving project will be an excellent, safe, all weather driving surface.  If you choose one of the new textured (open-graded) surfaces (friction course), your asphalt paving project will also reduce the amount of splash and spray during rainstorms, greatly improving driver visibility.  The black surface also helps in the visible delineation of lanes and pavement markings.

During construction, shorter lane closures also mean greater safety for workers and vehicles traveling through the work zone.  (To say nothing of the stress associated with long, long traffic delays in work zones.)

We all appreciate a smooth ride, but you may not be aware of the many cost, longevity and technical advantages that the smoothness of your asphalt paving project will provide.

A Vicious Cycle

It’s a continuing problem.  A rough pavement results in cars and trucks “bumping” the pavement more.  More “bumping” causes more pavement damage.  And so on, and so on, and so on.  You probably already know that asphalt pavements are smoother than concrete pavements, but the proof is that asphalt pavements have more stringent requirements for smoothness than concrete ones—because they can.  By building a smooth surface, your asphalt paving project will stop this cycle, resulting in lower maintenance costs, lower vehicle operating costs, fewer customer complaints and a longer lasting project.

Hint:  Reputable contractors know the value of pavement smoothness, and they know and use the quality techniques and construction practices to achieve it.  Be sure that you select such a contractor for your asphalt paving project.

Qualifying Smoothness

How smooth is smooth?  Engineers have found the best way to quantify smoothness is by measuring the roughness—the amount of vertical dislocation over a given length of pavement.  One of the most common measurements is the International Roughness Index (IRI), which is specified by the Federal Highway Administration and State DOT’s.   IRI is a measure of pavement roughness over a defined pavement length.  It is usually expressed as inches per mile or meters per kilometer.  An IRI of less than 60 inches/mi is generally considered a “good” pavement for an asphalt pavement.  Most road owners use some type of rating system (Present Serviceability Index-PSI or Pavement Condition Index—PCI or Pavement Quality Index—PQI) to determine pavement quality, and IRI (or some other roughness parameter) is one of the inputs to determine that index.  Other inputs include cracking, patching and rut depth.  The PSI scale ranges from 0 through 5, with 5 representing the highest level of serviceability.  New asphalt pavements typically have PSI values between 4.0 and 4.5.  Pavements typically need resurfacing when the PSI value drops between 2.0 and 2.5.

Benefits of Smoothness

A 1991 study showed a positive correlation between smoothness and long-term pavement performance.  Data from 10 years of performance on 400 different pavements demonstrated that initial smoothness is related to both long-term roughness and long-term cracking; as initial pavement smoothness decreases (initial roughness increases), the roughness after 10 years increases and the percentage of cracking after 10 years similarly increases.  The study also concluded that pavements that have higher initial smoothness result in maintenance savings as much as $1,200 per mile when the initial PSI is increased from 4.0 to 4.5.  Most road agencies acknowledge this, adding specifications for IRI for new surfaces, and even sometimes give bonuses for smoothness.  As any driver will attest, smoothness also means greater safety.

The Costs of Roughness

Researchers have documented that high IRI’s decrease the fuel efficiency of vehicles, cause higher consumption of oil, increase tire wear, and increase costs of maintenance and depreciation.  For example, fuel consumption increases about 10 percent for cars and 15 percent for buses if the PSI drops from 4.5 to 2.5.  Maintenance and tire costs can triple, and oil consumption will nearly double.  The net cost increase has been calculated to be $250-300 per 10,000 miles of driving.

The bottom line  is that smoothness equals lower vehicle maintenance costs and pavement maintenance costs.

Related Information

• Smooth Pavements Save Fuel
• Smoothness Specifications