THE FLEXIBLE WAY FORWARD

The new emphasis on best value and sustainabilitiy in road construction in the UK is described. Use of recycled materials, secondary binders, secondary aggregates, engineered foundations and innovative designs is more prevalent, with pavement designs falling between conventional fully flexible and flexible composite designs. The main limitations of the conventional mechanistic-empirical pavement design method is that it involves two distinctly different design methods, it can only deal with a limited number of materials and design configurations, no credit is given for stronger foundations, slow curing materials are not accommodated and long life design is reached at different traffic levels for flexible and flexible composite pavements. Modifications to the current design method are proposed including a single design criterion that limits the flexural stress or strain ta the underside of the base to a permissible level to achieve the required pavement life. Pavement design will be carried out in two stages, firstly the foundation and secondly the properties of the constructed foundation will be used in an analytical model to design the pavement structure. This design procedure will be incorporated into the Design Manual for Roads and Bridges along with standard designs that will be available for smaller schemes. It is considered that the adoption of the new design procedure will encourage innovation.