DUST PREVENTION AND ROAD PRESERVATION, 1915. 



53 



Table 51. — Analysis of asphaltic petroleum used on experiment No. 7. 



Specific gravity 25°/25° C 0. 958 



Flash point, °C 32 



Burning point, °C 81 



Viscosity, Engler, 25° C, 50 cc. specific 96. 8 



Loss 5 hrs. at 163° 0. 20 grams, per cent 25. 57 



Float test on residue at 50° C, time V 13^^ 



Per cent of total bitumen insoluble in 86° C. naphtha 5. 38 



Fixed carbon, per cent 3. 60 



Soluble in CS2 (total bitumen), per cent 99. 90 



Organic matter insoluble, per cent .08 



Inorganic matter insoluble, per cent .02 



Total, per cent 100. 00 



Table 52. — Mechanical analysis of sand used on experiment No. 7. 



Per cent. 



Passing ^-inch screen, retained on ^-inch screen 10. 6 



Passing ^-inch screen, retained on 10-mesh sieve 5. 3 



Passing 10-mesh sieve, retained on 20-mesh sieve 10. 8 



Passing 20-mesh sieve, retained on 30-mesh sieve 9. 8 



Passing 30-mesh sieve, retained on 40-mesh sieve 13. 3 



Passing 40-mesh sieve, retained on 50-mesh sieve 12. 1 



Passing 50-mesh sieve, retained on 80-mesh sieve 20. 5 



Passing SO-mesh sieve, retained on 100-mesh sieve 5. 3 



Passing 100-mesh sieve, retained on 200-me8h sieve 2. 9 



Passing 200-mesh sieve 9. 4 



Total 100. 



The traffic census has been continued, regular counts being taken 

 every 13 days. The point of observation was changed on June 26, 

 1915, so as to give better control, and the period of observation was 

 reduced to 16 hours. A tabulation of the maximum, and average of 

 each class of traffic for the period between June 26, 1915, and Febru- 

 ary 28, 1916, is given in Table 53. Traffic south of the census sta- 

 tion is on experiment No. 1, that north of the station is on experi- 

 ments Nos. 2 to 7, inclusive. 



Table 53. — Volume and character of traffic on Rockville Pike at the north end ofsedtion 1. 



Vehicle. 



Ix^fled 1-horse wagon... 

 Unloaclci 1-horse wagon . 



I^oaflftd 2-horse wagon 



T;nl(-/ifl<id 2-horse wagon . 

 L'/dih'A 4-horse wagon.. . 

 Unl'/aded 4-horse wagon. 

 l-hdrm pleasure vehicle. . 

 2-hor -n ji]vi.-:ur(i vehicle. . 



I . tif^vy vehicle. 



Motor rijri:ibout 



Motor touring car 



IxjutlcA motor dray 



Unlf^aded motor dray 



Sections 2 to 7. 



Maximum. 



North- South- 

 bound, boimd. 



18 

 9 



22 



10 



1 



3 



14 



1 



19 



48 



2 



74 



381 



26 



10 



16 

 16 

 22 

 3 

 3 

 15 

 2 

 7 



78 

 2 

 90 

 628 

 26 

 13 



Average. 



North- South- 

 bound, bound. 



4 



16 



"24' 



117 



1.5 



3 



4 

 17 



"26' 

 126 



16 

 6 



Section 1. 



Maximum. 



North- South- 

 bound, bound. 



30 

 18 

 69 

 15 

 2 

 6 

 30 

 1 



18 

 55 

 14 

 88 

 442 

 63 

 17 



13 

 27 

 24 

 44 



7 



2 

 28 



2 

 25 

 71 



5 

 104 

 582 

 43 

 48 



Average. 



North- South- 

 bound, bound. 



16 

 8 



25 

 5 



'"i 



15 

 ..... 



22 

 2 



35 

 163 



31 

 7 



