The concrete industry is concerned that it may lose more of its already small concrete paving market because mechanistic design methods used in Illinois may spread to other states. Mechanistic methods used by the Illinois Department of Transportation (IDOT) require thicker concrete pavements than would be required if conventional design procedures were used. Asphalt pavements designed by IDOT's mechanistic methods, on the other hand, are generally thinner than those designed by other procedures. Critics say the designs aren't comparable and the maintenance and rehabilitation costs used in life-cycle cost comparisons aren't supported by actual performance data. Because of this, they say, the pavement selection process that's a part of IDOT's design method favors asphalt over concrete.
Representatives from the concrete industry, as well as several independent consultants, believe the Illinois method is seriously flawed. To deal with the problem, concrete industry leaders have formed the National Coalition for Mechanistic Design (NCMD). This group promotes the proper technical aspects of mechanistic designs for asphalt and concrete pavements to ensure that design procedures for both pavement types are comparable and equitable. It will also present the concrete industry's position to state and federal agencies.