After the Strategic Highway Research Program was conducted, the U.S. National Research Council, confirmed that spray injection patching is the fastest, most durable and least expensive means of pothole repair, while most agencies continue to use "throw and go" methods for a majority of their road concerns.Ray Rugh, highway equipment manager and chief of specifications for the Pennsylvania Department of Transportation, has witnessed a growing acceptance of spray patching technology.The "throw and go" method, which long ago was common in Pennsylvania, is now very rare. "Since [the spray patcher] is a better method of repair, we are trying to eliminate "throw and go" patching as much as possible.""The patches that we've been replacing with the spray patchers have been holding for about three to four years," Rugh added, "Whereas the "throw and go" method is a quick way to take care of the hole today, it will generally cause a problem again tomorrow."

Spray Patching is done in four steps. First, using a high-volume blower, the pothole is cleaned, removing loose rock, debris, and moisture. Next, a tack coat of hot emulsion is applied to the area that needs to be patched. Third, a mixture of aggregate and hot emulsion is shot into the hole to fill the depression. Lastly, a top layer of dry aggregate is applied and traffic can flow immediately.

UNDER SCRUTINY
Illinois has been scrutinizing the spray injection method as well. Brandon Long, specifications and development specialist for the Illinois Department of Transportation (IDOT), has recently compiled some compelling statistics about the spray injection's capabilities. After almost three years of use, it was found that on interstate patching applications, the spray injection repair lasted up to four times longer than a "throw and go" repair. But on primary roadways where there is less heavy-truck travel and average daily traffic, the spray injection patches lasted up to ten times longer.