4(J THE TESTING OF KG AD MATERIALS. 



into the bunds of the engineer preliminary data on which to base his 

 calculations and estimates. It is hoped that before long intelligent 

 cooperation will make this true of road building. To this end the 

 laboratory has decided on the following plan to govern its future work. 

 It will require a few years for the completion of the plan, but by fol- 

 lowing it until a better one is evolved the usefulness of the laboratory 

 should constantly increase. 



As it is impossible to accurately judge the quality of a road material 

 unless the conditions of climate and traffic on the particular road where 

 it is to be used are known, it is intended to secure such data as far as 

 possible. For this purpose a form/' for making a census of the volume 

 and character of traffic on any road has been prepared. The cost of 

 such a census is trifling when the total cost of the road is considered, 

 and the observations ma} T be made by anyone living within view of the 

 road. When enough of these records have been accumulated, the traffic 

 of a road may be expressed by a number, if a unit and standard scale 

 are agreed upon to suit the average conditions of the country as has 

 been done in France. The maximum, minimum, and mean conditions 

 of temperature, rainfall, and wind velocity for any locality can he 

 obtained from the Weather Bureau, and also classified according to a 

 similar scale. When a large number of standard results of different 

 tests have been accumulated and compared with the results of prad ice. 

 it will be possible to classify them into tive groups to correspond to 

 the live subdivisions of traffic. Thus, when a test sample is received 

 at the laboratory, together with a census of the trallic on the road to 

 be constructed, the traffic and climate will be placed in their proper 

 groups and the hardness, toughness, resistance to wear, cementing 

 value, weight per cubic foot, and absorptiveness will each be graded 

 according to the same standard scale. By this method the best avail- 

 able material for any road can be selected with a high degree of accu- 

 racv. for the proposed classification will be based on the observations 

 of practice a> well as on laboratory tests. Such results can not fail to 

 be of the bio-hot value to the road engineer. 



page 77, Api>eii<lix. 



