DUST PREVENTION" AND 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) . 
Cost per square yard. 
Total cost. 
6 
S 
CD 
B 
eo 
ft 
X 
Bituminous 
material. 
o 
co 
bO 
o 
o 
co 
o 
CD 
< 
a 
CO 
O rt 
is 
3 
> 
03 
a 
a 
CO 
3 
s 
"3 
> 
u 
o 
<d 
o 
«S 
3 
co 
bo 
.3 
a 
o3 
O 
■-3 2 
o 
A 
bo'd 
fl 3 
ft 
bo 
ft 
02 
bo 
a 
CO 

O 
CD 
PI 
"3 
o 
CO 
03 
t>» 
CD 
(-1 
a 
c 
CO 
o 
o 
ft 
1 
Refined coal tar 
(hot) 
Feet. 
6,105 
7,380 
7,400 
7,100 
6,775 
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 
.0138 
.0138 
.0138 
.0138 
4.35 
2.85 
2.35 
3.29 
3.31 
3.72 
3.33 
Cts. 
3.01 
3.01 
3.01 
3.01 
3.01 
3.01 
3.01 
cts. 
0.30 
.30 
.30 
.30 
.30 
.30 
.30 
Cfe. 
1.22 
.09 
.09 
1.22 
1.22 
1.22 
.09 
CYs. 
0.53 
.37 
.37 
.53 
.53 
.53 
.37 
Cfe. 
0.55 
.55 
.55 
.55 
.55 
.55 
.55 
as. 
0.05 
.05 
.05 
.05 
.05 
.05 
.05 
as. 
0.92 
.92 
.92 
.92 
.92 
.92 
.92 
10.93 
8.14 
7.64 
9.87 
9.89 
10.30 
8.62 
$961. 84 
2 
3 
4 
Refined water-gas 
tar (cold) 
Asphaltic petrole- 
um (cold) 
Residual asphaltic 
petroleum (hot). 
Do 
716. 32 
672. 32 
868. 56 
870. 32 
6 
7 
Water-gas tar prep- 
aration (hot) 
Asphaltic petrole- 
um (cold) 
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 8248.16 
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 + 00, 
I 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 
