REPORT OF THE SECRETARY. Ill 



many perplexing questions in liiglnvay technique and in the plan of 

 administration and finance for public highways. The work of the 

 Office of Public Roads of this department has fortunately kept pace 

 with the widespread demand for information and assistance in road 

 matters. 



OBJECT-LESSON AND EXPERIMENTAL ROADS. 



There have been built during the present fiscal year 32 object- 

 lesson roads under the direction of engineers from this office. Such 

 roads include plain maCadam, oiled macadam, bituminous macadam, 

 gravel, sand-clay, and earth roads. The office has also supplied 

 supervision for the erection of three bridges. Twenty-four object- 

 lesson roads built during past years have been inspected for informa- 

 tion to guide future work. Some of these roads are in good shape, 

 some show lack of maintenance, but nearly all have proved a stimu- 

 lus in awakening interest for better methods of construction. Eight 

 sections of experimental roadway were constructed at Chevy Chase, 

 in Montgomery County, Md. These sections were built for the pur- 

 pose of determining the relative merits of different forms of bitu- 

 minous material used as binders and dust preventives on macadam 

 roads. A careful traffic census has been taken each thirteenth day 

 since the completion of the work. It is planned to keep accurate 

 records of the cost of maintenance of the various sections and prop- 

 erly to relate such costs to the traffic sustained by the road. 



ECONOMIC INVESTIGATIONS AND MODEL SYSTEIMS. 



There has been an increasing demand for extended inspection by 

 the engineers of the office in various counties. With a view to de- 

 velop proper model systems of highways, engineers have been as- 

 signed to 24 counties. After thorough examination of existing 

 conditions, detailed reports and recommendations have been prepared 

 and submitted. It is necessary in this work to inspect thoroughly 

 the entire county system; to determine the location and quality of 

 road materials; to select the particular roads which carry the main 

 traffic; to examine the financial resources and the plan of road ad- 

 ministration and maintenance; and, wherever possible, to prepare 

 maps and sufficient working drawings. Reports submitted to the 

 authorities include all necessary details for carrying out proposed 

 plans of improvement. This model system work has proved one of 

 the most effective ways in which the Office of Public Roads has been 

 able to impart information and render expert service. 



SPECIAL INSPECTION AND ADVICE. 



The office is frequently called upon by road officials and other 

 administrative officers in towns and counties to supply quick advice 



