22 BULLETIN 257, U. S.. DEPARTMENT OF AGRICULTURE. 
TasiE 14.—Volume and character of traffic on Rockville Pike at its intersection with: 
Bradley Lane. 
Maximum, Average. 
Vehicle. : 
North- | South- | North-| South- | 
bound. | bound. | bound. | bound. 
Woaded: I-horsewwasons ons Fae aS ee re ee ree Me roe Sy eee 25 23 13 13 
Mnloadedsi-WorserwacOin a Re oc ae aren inc a ol we elole Bis eee eee 26 26 12 il 
Woaded)2-horse “wacom cio2e ied ts Leen Dee een eee le ee Ee 3l 71 i3 27 
Wnloaded22-horse wacon. =... aoe. 220 soon cee noe eee geet eines 59 14 20 6 
Poaded-4-horse wagon: <5 2e SS Gos MPa we at ae ne Pr omen oi ee 4 + 1 1 
Wmnload@edc4shorserwaso as. siascs< eek c Beste oe ee See ee ee Sees 5 3 1 0 
Hohorsompleasure venicle 2252.52. ° laze. cae See ene ee eee eee - 22 24 12 14 
2-horse-pleasure Vehicle. ccc... 2 kes erates eee eee eee 5 5 1 2 
Rub bersbired horse :Vebicle 27. 2c ccer eras eas Wace oe Recess ee roan eee 3 ak 880 0. 
Sad dlomorse sass eo sick sacs oe wise re cer reare nates eS a ote ara meee 18 19 5 5 
IMOtOMGY ClO S24 osc oe is Se ee Ee: Sse Ea ert era 39 35 20 18 
IBEXCESSIMeLy: HEAVY VieMICl GO: -e saps sin wae wiaie ara ce ee Snare eee eee eee 12 18 3 4 
IMOLOPTUNADOUG2 Sr 22 chee A ot Sr eee crys ee $8 SE 42 42 
MOUOESUOURIN SICAT Se ea oo eres Ste gs ya fas nrarets eaten ere te te ae 243 187 96 89 
Loaded motor dray........-- BURA SEES NS ee Meas Meee alee ee ER eee ee ee 24 38 12 16 
Unloaded motor dray. SOR SGO Lo UR ae Been eBid aoe ie ee mene aS ce aa: 29 12 7 5 
The total cost of maintenance and cost to date of each experiment 
are shown in the following table: 
TABLE 15.— ee cost of experiments on Rockville Pike, Maryland, io December 
SLE TOTES 
| 
le Surface2 | Total cost) : 
. inte- | of surface} Surface | Total 
EXx- Cost’ per | ape | : : 
: | a nance per mainte- | mainte- 
veent| Bituminous material. eeae ries ets per square | nance per| nance per 
No. (cents). square | yard to mile for mile for 
yard Dec. 31, | lyear. 1 year. 
(cents). 1914. 
. 1913. : 
1 | Refined coal tar (hot)... Sept. 22 6, 105 12.34 1.58 13.92 | $139.04 $332. 93 
2| Refined water-gas tar 
(Cold) Rea se eae Sept. 24 7, 380 9. 55 7.56 i7ei ut 665. 28 739. It - 
3 pe ouetee petroleum 
(COld) Res8s5a-saee se toes Sept. 30 7, 400 9. 05 6. 00 15. 05 528. 00 576. 26 
4 | Residual asphaltic pe- 
troleum) (hot)... 225-2242 Oct-15 7,100 11.28 1.61 12. 89 141. 68 215. 18° 
5 DKON cea Gees ees Nov. 21 6,775 11.30 2. 00 13. 30 176. 00 237. 37 
6 | Water-gas tar prepara- 
OM (nO b) ape eee ace Nov. 26 G53250 jee eee 1.88 > 13..59 165. 44 219, 47 
7 | Asphaltic petroleum 
(Cold era cece es Decsa5 6, 689 10.03 | - 57a 10. 74 | 62. 48 106. 82 
1 Average for trap and gravel. 2To 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. 8S. 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 
