IRC:81-1981 PROVIDING TENTATIVE GUIDELINES REQUIRED FOR THE STRENGHNING OF FLEXIBLE ROAD PAVEMENTS USING BENKELMAN BEAM DEFLECTION TECHNIQUE .

ANALYSIS OF DATA FOR OVERLAY DESIGN (IRC :81-1981):-- CHARACTERISTIC DEFLECTION :-- Overlay design for a given section is based not on individual deflection values but on a stastical analysis of all the ten measurements in the section corrected for temperature and seasonal variations .This involves calculation of the mean deflection, standard deviation and the characteristic deflection. The characteristics deflection for all design purposes should be taken as the mean deflection plus one standard deviation and used for the recorded proforma based on the analysis of test data prescribed  . TRAFFIC  PROJECTION :-- The purposes of this design method, the traffic is considered in units of heavy vehicles (Vehicles with a laden weight of 3 tonnes or more) per day , in both the directions in the case of two lane roads and in the direction of heavier traffic in the case of multi - lane divided highways .Based on the present traffic, the design traffic ,ie the traffic accepted at the end of the design your should be estimated. In preparing these estimates due consideration should be given to the existing traffic, possible changes in road net work and land use of the area served , and probable growth of traffic during the period of projection under consideration .It is considered appropriate that major through routes should be designed for at least 10 years of life .Less important roads may , however , be designed for a some what lower period based on growth prospects and may be obtained from the formula based on the traffic count figure normally seven days average for commercial vehicles derived from 24 hours counts .However ,in exceptional cases where this information is not available,an average of three days counts could also be used to obtain the result sheet.