356 AGRICULTURAL APPROPRIATION BILL, 1924. 



Mr. Anderson. I have noticed a very considerable variation in 

 the character of the roads resultino^ and the methods adopted in 

 putting gravel on tiiem. Have there been any experiments which 

 nave developed the relative strength of the road resulting from 

 different kinds of gravel or methods which are more successful in 

 putting tliem on, or do you simply use what you can get '. 



Mr. MacDonald. The bureau has been making a very extensive 

 series of studies of the behavior of gravel roads; in fact, some very 

 good studies are now ready for j)umication. It is true that in the 

 building of gravel roads on many of the main highways we have 

 used the local materials which could be secured at the lowest cost 

 even though not first class in quality. In such cases it is not ex- 

 pected to maintain the gravel surface hulefinitely. but it does pro- 

 vide a temporary wearing surface while the newly built road grade 

 is becoming compacted. As soon as the road bed is ready, or as 

 soon as funds are available, paved surface is placed. If it is the 

 intention to maintain the gravel road, more care is used hi selecting 

 and preparing the material. 



Up to the present time in most of the States the Federal-aid work 

 has been almost entirely on the main roads of the country, either con- 

 structing or reconstructing them. It is not physically practicable 

 and funds are not available for building only paved roadways, 

 thus we have been carrying forward the grading, draining, and pre- 



faratory work in advance of the more durable forms of surfacmg. 

 t is possible to do this type of improvement on a larger mileage each 

 year than it is to follow up w^ith the construction of paved-road sur- 

 faces. Also, it is in general better engineering if traffic conditions can 

 be met to build the roadbeds some time in advance of the surfaces, and 

 that plan has been widely used in all of the States where it is possible 

 to obtain local materials for interim use, such as gravel, sand, clay, 

 and similar materials. The difference in the service to the public and 

 the saving in the cost of maintenance is considered to offset the cost 

 of applying materials of this character. 



The probabilities are, Mr. Chairman, in answer to your question, 

 that the differences in results which you observe on different gravel 

 roads, while partially due to the kind of materials used, are in a 

 greater percentage of cases due to variations, first, in the character 

 of the subgrade, and, second, in the traffic. 



FOR MAINTENANCE AND REPAIRS OF EXPERIMENTAL TIIOnWAYS. 



Mr. Anderson. Your next item is for maintenance and repairs of 

 experinicntal liighways. I imagine that is a good ileal of a misnomer, 

 is It not { 



Mr.MAcDoNAi.D. No, sir; our expenditures last year were nil on 

 ex|)eriniental highways that we had built, although our principal 

 cxpnidit lire was on the Mount N'ernoji road leading from tbe paved 

 road inl(» tlie grounds at Mount X'ernon. That road was originally 

 built as a surface-treated grav(>l road, and we have foinid it necessary, 

 with tlic heavy trallic which has l)een developed, to iegra<le and 

 icbiiild a part. It is true tliat the gravel road is g(»ing to be an ex- 

 pt'iisive type t<t iiiiiiiitnin, but it would not be possible within any 





