• Modified polymers used to enhance the binders in asphalt have been limited to a maximum of 4% because of manufacturing and performance factors.
• Kraton, a polymer-maker based in Houston, is testing a new "highly modified asphalt" that has 8% polymers mixed with the aggregates and holds the promise of reducing the thickness of paving by 30% to 50%.
• State agencies that have been working with Kraton to test the new polymers say it can be used without new equipment or processes and that longer road life will offset higher up-front costs.

From the article:

Highly modified asphalt is undergoing trials across the U.S. as agencies seek to make roads safer and more durable while cutting overall costs. ...