DUST PREVENTION AKT> ROAD PRESERVATION". 



23 



The cost data given in Table 28 are based upon the following unit 

 prices for labor and materials : 



Foreman (per 8-hour day) $4. 00 



Distributor operator (per 8-hour day) 4. 00 



Fireman (per 8-hour day) 2. 00 



Laborers (per 8-hour day) 1. 60 



Teams (per 8-hour day) - 4. 00 



Traction engine (per day) 10. 00 



Gravel, on siding (per ton) 1. 75 



Trap rock, on siding (per ton) 3. 35 



No charge was made for distributor or other implements. 



Table 28.— Materials and cost data for surface treatment experiments on Rockville Pike. 



Description. 



Quantity 

 of ma- 

 terials 

 (per square 

 yard). 



Bituminous 

 material. 



O c3 



■S'S 



Cost per square yard. 



S+ 3 



S]eS 



.ITS 



<D 2 



Total cost. 



~ O 



Refined coal tar 

 (hot) 



Refined water-gas 

 tar (cold) 



Asphaltic petrole- 

 um (cold) 



Residual asphaltic 



petroleum (hot) 



Do 



Water-gas tar prep 

 aration (hot) 



Asphaltic petrole- 

 um (cold) 



Feet. 

 6,105 



7,380 



7,400 



7,100 

 G,775 



6,325 



6,689 



Sq. 



yds. 



10, 175 



12,300 



12,333 



11,833 

 11,292 



10, 542 



11,148 



Gal- 

 lons 

 0.531 



.438 



.470 



.473 

 .496 



.531 



.502 



Cu. 



yds. 



0. 0138 



.0138 



.0138 



.0I3S 

 .0138 



.0138 



.0138 



Cts. 

 4.35 



2.85 

 2.35 



3.29 

 3.31 



3.72 

 3.33 



Cts. 

 3.01 



a oi 



3.01 



3.01 

 3.01 



3.01 

 3.01 



as. 



0.30 



.30 

 .30 



..30 

 .30 



Cts. 

 1.22 



1.22 

 1.22 



Cts 



a 53 



.3 

 .37 



.53 

 .53 



.53 

 .37 



Cts. 

 0.55 



.55 

 .55 



.55 

 .55 



Cts. 

 0.05 



.05 

 .05 



.05 

 .05 



as. 



0.92 



.92 

 .92 



.92 

 . 92 



.92] 

 .92 



Cts. 

 10.93 



8.14 



7.64 



9.87 

 9.89 



10.30 



S.62 



$961. 84 



716.32 



672. 32 



868. 56 

 870. 32 



906. 40 



758. 56 



i The costs in this table are based on finishing with gravel. The trap-rock screenings were applied at 

 the rate of 0.0132 cubic yard per square yard at an additional cost of 2.82 cents per square yard, or S24S.16 

 per mile of 15-foot road. 



SUMMARY OF EXPERIMENTS ON ROCKVILLE PIKE. 



These experiments were carefully inspected on January 7 and 

 again on April 2 ; 1914. It is, of course, too early to draw any con- 

 clusions regarding the relative value of the several treatments. 

 From a consideration of the present condition of all the sections, it 

 would appear that the trap rock and gravel have given equally good 

 results. Experiment No. 1, which has been under traffic the longest, 

 has developed a smooth, firm surface with but few defects, and 

 these are slight. There has been, however, a decided settlement of 

 the road along the west shoulder in the vicinity of station 12 4-00, 

 and this has resulted in the surface breaking along the edge. Experi- 

 ment No. 2 has also developed a generally smooth surface. Toward 

 the north end of this experiment, the surface treatment has worn 



