Recent initiatives in asphalt pavement design have produced a new approach to road building that could extend the design life of an asphalt pavement to 50 years or more—while improving safety and cutting both the time and cost of construction and maintenance.

Perpetual Pavements are asphalt pavements that use multiple layers of durable, recyclable asphalt. They stand up for decades under the steady punishment of heavy trucks. In addition, they provide a consistently safe and smooth roadway for parents driving minivans full of kids to soccer. When the surface layer needs repair, structural additions, or maintenance, it can be milled off for recycling and replaced in a timely and cost-effective manner. But the road structure never needs to be entirely removed and replaced.

Developed by the Hot Mix Asphalt (HMA) pavement industry, Perpetual Pavements meet the driving public''s demand for durable roads that won''t crumble under today''s increasing traffic and thus won''t need costly and disruptive reconstruction. The concept is similar to that of a house that periodically may need to be painted or re-roofed, but that still stands the test of time.

People will endure an incredibly poor-riding highway rather than undergo the disruption of a reconstruction project, Gary Whited, Director of the Wisconsin Department of Transportation''s Bureau of Highway Construction, told a recent highway seminar. Overwhelmingly, they tell us their priority is longer-lasting pavements.

Perpetual Pavements constructed of Hot Mix Asphalt satisfy that priority. The design starts with strong HMA base layer, flexible enough to prevent bottom-up, structural fatigue cracks. A strong load-bearing layer is applied over that, and the surface is constructed with a special asphalt mixture designed to resist ruts. This sturdy pavement system is designed to prevent the need for reconstruction for 50 years or more. The surface can be periodically milled off for recycling, then quickly replaced, effectively giving motorists a new road.

In this concept, pavement distress is forced to the surface where it can be dealt with easily, explained Jim Huddleston, Executive Director of the Asphalt Pavement Assn. of Oregon. Basically, we can then just resurface periodically to keep users happy. This approach also eliminates the need for total reconstruction or thick overlays in the future.

That projected lifespan is a significant improvement over much of the nation''s freeway system, built in the 1960s and 70s, and expected to serve for about two decades or less, Huddleston added. And those projects were planned and built before today''s heavier vehicles and increasing truck volumes took to the road.

As a long-lasting and smoother paving material, Perpetual Pavements using HMA could spell dramatic savings for state and federal transportation agencies striving to balance tight road budgets. And, because asphalt pavements are 100 percent recyclable, Perpetual Pavements offer further cost advantages as well as environmental benefits.