BUREAU OF PUBLIC ROADS. 475 



No record of the year's work would be complete which did not 

 make special mention of two cooperative projects that have attracted 

 world-wide attention. The bureau cooperated with the Illinois De- 

 partment of Public Works and Buildings in securing the experi- 

 mental data at the Bates experimental road, near Springfield, 111. 

 For the construction of the 2-mile section of experimental roadway 

 and the enterprise and vision which made the road possible entire 

 credit is due to the State authorities, but the bureau rendered assist- 

 ance by assigning engineers and apparatus and cooperated with the 

 State officials in the stud,y of the experimental data. 



The other notable cooperative experiment is that which has re- 

 cently been completed at Pittsburg, Calif. This project was initiated 

 by the Columbia Steel Co. in the spring of 1921. From the begin- 

 ning it has been under the observation of engineers officially assigned 

 by the bureau and the California Highway Commission, and a num- 

 ber of the designs for concrete road sections had been made bj^ the 

 two public agencies. When it became apparent that the project 

 needed assistance in securing the necessary trucks to accelerate the 

 test, the bureau and the State commission supplied the need. 

 Finally, in 1922, when the test indicated results of considerable use- 

 fulness to all road-building design, formal financial cooperation of 

 the California Highway Commission and the bureau was arranged 

 to complete the test and publish the results. The report of the test, 

 recently published, is generally considered to be one of the outstand- 

 ing contributions to highway engineering knowledge. 



In both the Pittsburg and Bates road tests the project consisted 

 of the testing of various types and designs of pavement under actual 

 truck traffic. While the results obtained were more or less dependent 

 upon the local subgrade conditions, they are applicable directly to all 

 similar conditions in the United States, and with suitable modifica- 

 tions everywhere. 



The policy of taking part in these cooperative projects furnishes 

 the means of securing the services of the foremost investigators in 

 particular fields, as well as personnel and the use of equipment not 

 available in Washington. To a considerable extent it has the effect 

 of coordinating the efforts of the various organizations into a con- 

 certed attack on urgent highway problems. 



ROUTINE TESTING OF HIGHWAY MATERIALS. 



In addition to the research work, the bureau has continued to make 

 routine laboratory examinations of various materials used in road 

 construction. During the fiscal year 1,686 samples of road material 

 were examined in the laboratories — 1,038 in the physical laboratoiy 

 and 648 in the chemical laboratory; 1,000 of these samples were of 

 materials intended for use on specific Federal-aid projects; the re- 

 mainder were miscellaneous materials submitted by individuals or 

 corporations for the purpose of determining their general suitability 

 in road construction. 



One thousand and nine samples of nonbituminous materials were 

 examined and classified in the petrographic laboratory, including 

 835 samples of rock, 177 of gravel, 310 of sand, and the balance 

 miscellaneous materials. 



Cooperation with various State, university, and commercial labo- 

 ratories engaged in the examination of materials for Federal-aid 

 roads has also been continued. This is done to secure and maintain 



