52 BULLETIN 586, U. S. DEPARTMENT OF AGRICULTURE. 
Expervment No. 6— Water-gas tar preparation, hot application.— 
The re-treatment of this section in November, 1915, put the surface 
in first-class condition and at the time of inspection it showed little 
wear, no breaks, and only a few small areas where moisture had per- 
meated the mat. In general, the surface remained in fine condition. 
Experiment No. 7—Asphaltic petroleum, cold application.—As con- 
templated in the last report, this experiment required re-treatment 
early in July, 1916. The characteristics of the bituminous material 
used are given in Table 52 and the quantities and cost data are given 
in Table 53. At the time of inspection the surface was in good con- 
dition for the season. It had not become so muddy as usual and the 
mat was much more uniform. ‘Traffic census had been continued, 
regular counts having been taken for a 24-hour period every thir- 
teenth day. A tabulation of the maximum and average of each class 
of traffic for the calendar year 1916 is givenin Table 55. Traffic south 
of the census station is on experiment No. 1 only; that north of the 
station is on experiments Nos. 2 to 7, inclusive. Maintenance by 
patrolmen was continued during the year and Table 54 shows com- 
parative cost data to December 31, 1916, for the various experiments 
included in this project. 
TasBLE 55.— Volume and character of traffic on Rockville Pike. 
° Section 1. Sections 2 to 7. 
Maximum. Average. Maximum. Average. 
North | South | North | South | North | South | North | South 
bound. | bound.} bound.| bound.| bound.| bound.| bound.| bound. 
1 | Loaded 1-horse wagon.......--- 30 18 18 9 22 il 10 5 
2 | Unloaded 1-horse wagon..--..-- 17 31 7 14 | 8 17 4 7 
3 | Loaded 2-horse wagon..--.-----. 46 20 28 14 29 14 6 3 
4 | Unloaded 2-horse wagon...-.-.-- 15 41 4 13 6 28 2 4 
5 | Loaded 4-horse wagon..-. 5 6 1 1 § 5 | Iapascsce 1 
6 | Unloaded 4-horse wagon. . 4 3 1 |..-.-.-- 4 1 |.......-|-------- 
7 | 1-horse pleasure vehicle.-....... 22 21 12 il i 14 5 5 
8 | 2-horse pleasure vehicle.......-. 2 1) | Bee eoesel SoBooees 1 Ue ee es ee ae 
9 | Rubber-tired horse vehicle...... 2 D2 a ee) Decale 1 i Ee Silt eae ae 
10 | Saddle horse.......--.-.-------- 11 21 5 6 7 16 2 3 
1) Motorley cle ier- prea seeesa a 74 71 17 19 57 61 15 15 
12 | Excessively heavy vehicle!.... 23 7 2 1 3 Ca Paeecae Gacadeie 
13 | Motor runabout. ...-.---------- 105 110 50 50 82 87 34 33 
14 | Motor touring car.....-.-..--.-- 694 793 209 216 611 700 158 164 
15 | Loaded motor dray....--.---..- 66 55 40 32 41 46 23 23 
16 | Unloaded motor dray...,-.----- 16 42 5 13 12 12 3 5 
1 Very heavy vehicles, such as carry ore, stone, timber, machinery, etc. 
WASHINGTON, D. C., 1912. 
TAR PREPARATION AND OILS, SURFACE TREATMENT. 
The original report of these experiments was published in Circular 
No. 99 of the Office of Public Roads, and inspection reports have 
appeared in Bulletins Nos. 105, 257, and 407, U. S. Department of 
Agriculture. The following report describes the maintenance during 
the year 1916 and the condition of the experiments March 28, 1917. 
