22 



BULLETIN 257, U. S.- DEPAKTMENT OF AGRICULTTJKE. 



Table 14. — Volume and character, of traffic on Rockville Pike at its intersection with 



Bradley Lane. 



Vehicle. 



Loaded 1-horse wagon 



Unloaded 1-horse wagon . . 



Loaded 2-horse wagon 



Unloaded 2-horse wagon . . 



Loaded 4-horse wagon 



Unloaded 4-horse wagon. . 

 1-horse pleasure vehicle . . . 

 2-horse pleasure vehicle . . . 

 Rubber-tired horse vehicle 



Saddle horse 



Motor cycle 



Excessively heavy vehicle. 



Motor runabout 



Motor touring car 



Loaded motor dray 



Unloaded motor dray 



Maximum. 



North- 

 bound. 



25 



26 



31 



59 



4 



5 



22 



5 



3 



18 

 39 

 12 

 98 

 243 

 24 

 29 



South- 

 bound. 



23 



26 



71 



14 



4 



3 



24 



5 



2 



19 



35 



18 



91 



187 



38 



12 



Average. 



North- 

 bound. 



South- 

 bound. 



The total cost of maintenance and cost to date of each experiment 

 are shown in the following table: 



Table 15.— Maintenance cost of experiments on Rockville Pike, Maryland, to December 



31, 1914- 



Ex- 

 peri- 

 ment 



No. 



Bituminous material. 









Surface 2 



Total cost 









Cost 1 per 



square 



yard 



(cents). 



mainte- 



of surface 



Surface 



Date com- 

 pleted. 



Length 

 (feet). 



nance 

 per 



square 



per 

 square 

 yard to 



mainte- 

 nance per 

 mile for 







yard 



Dec. 31, 



1 year. 









(cents). 



1914. 





1913. 













Sept. 22 



6, 105 



12.34 



1.58 



13.92 



§139. 04 



Sept. 24 



7,380 



9.55 



7.56 



17.11 



665. 28 



Sept. 30 



7.. 400 



9.05 



6.00 



15.05 



528. 00 



Oct. 15 



7,100 



11.28 



1.61 



12.89 



141. 68 



Nov. 21 



6,775 



11.30 



2.00 



13.30 



176. 00 



Nov. 26 



6,325 



11.71 



1.88 



13.59 



165.44 



Dec. 5 



6,689 



10.03 



.71 



10.74 



62.48 



Total 

 mainte- 

 nance per 

 mile for 

 1 year. 



Refined coal tar (hot) . . 



Refined water-gas tar 

 (cold) 



Asphaltic petroleum 

 (cold) 



Residual asphaltic pe- 

 troleum (hot) 



Do 



Water-gas tar prepara- 

 tion (hot) 



Asphaltic petroleum 

 (cold) - 



S332. 93 



739. 11 



576. 26 



215. 18 

 237. 37 



219. 47 



106. 82 



i Average for trap and gravi 



To Dec. 31, 1914. 



SUPPLEMENTARY REPORT OF EXPERIMENTS AT WASHINGTON, 



D. C, 1912. 



TAR PREPARATIONS AND OILS— SURFACE TREATMENT. 



The original report of these experiments was published in Circular 

 No. 99 of the Office of Public Roads, and the inspection report for 

 the first year was given in U. S. Department of Agriculture Bulletin 

 No. 105. The following report gives the extent of the repairs during 

 1914 and the condition of the experiments when inspected on March 

 11, 1915: 



All four sections in the summer of 1914 showed considerable wear. 

 The surface mat of section No. 1 apparently was becoming somewhat 



