494 ANNUAL, BEPORTS OF DEPARTMENT OF AGRICULTURE. 



sachusetts Institute of Technology, North CaroHna State Highway 

 DepartmSit, and New Hampshire State Highway Department. We 

 have also worked in cooperation with the Illmois and California State 

 highway departments. The investigations conducted involve field 

 investigations of sand-clay roads, investigations of tractive resistance, 

 and laboratory investigations of the properties of road-making 

 materials. 



ROUTINE TESTING OF BITUMINOUS AND NONBITUMINOUS MATERIALS. 



In addition to the Federal-aid samples tested, tests were made by 

 the chemical laboratory upon 445 samples of bituminous material, 160 

 samples of metal, and 42 samples of miscellaneous materials. The 

 nonbituminous testing laboratory examined 1 ,283 samples of various 

 materials, including rock, sand, gravel, cement, concrete, slag, and 

 brick. In the petrographic laboratory 991 samples were examined, 

 including 431 samples of rock, 262 of gravel, 239 of sand, 19 of clay, 

 37 of slag, and 3 miscellaneous samples. In addition, the petrog- 

 rapher conducted a special investigation of the microscopic portions 

 of certain subgrade materials, in connection with which a special dye 

 adsorption test was developed for investigating the clay and sus- 

 pension clay portions. 



ECONOMIC INVESTIGATIONS AND RESEARCH. 



Recognizing the necessity of centralizing research in the fields of 

 highway transportation, finance and valuation plans have been made 

 for the organization of a division of highway economics as a separate 

 division of the bureau beginning with the new fiscal year. A certain 

 amount of investigational work has been done along these lines, but for 

 the last three years there has been no special section of the organiza- 

 tion charged with the responsibility of that particular kind of work. 



This year several very satisfactory studies have been made directly 

 under the office of the chief of bureau, the most prominent of which 

 were two traflic surveys conducted in cooperation with the Connecti- 

 cut State Highway Department on the Boston Post Road and the road 

 from Hartford, Conn., to Springfield, Mass. The survey on the Bos- 

 ton Post Road was made near Greenwich, Conn., and that on the 

 Hartford-Springfield Road was made near the Massachusetts line. 

 Certain very illuminating data with regard to the weight and number 

 of vehicles, the character of commodities transported by highway,. 

 and the length of haul by highway were obtained in those studies. 



During the summer of 1921 a survey of highway traffic, finance, and 

 valuation was conducted in cooperation with the University of Ten- 

 nessee and the highway department of that State in several Tennessee 

 counties. 



Both of these surveys, their scope somewhat extended, will be 

 continued during the next fiscal year, and it is expected that the Con- 

 necticut survey in particular will produce traffic data records on a 

 scale never before attempted. The survey will include the recording 

 of vehicle traffic and the movement of commodities over the high- 

 ways of the State for a period of a year, and it is hoped that it will 

 provide much of the highway transport data so fundamental in the 

 solution of modern highway problems. 



