DUST PREVENTION AND ROAD PRESERVATION, 1914, rival 
EXPERIMENT No. 6. (WATER-GAs TAR PREPARATION—HoT APPLICATION). 
This experiment bled rather freely in the spring and required con- 
siderable top-dressing and repairs, especially on the trap section. 
The surface does not become muddy, although dampness shows 
through along several areas where subdrainage is poor. Most of the 
repairs so far have been due to some little stripping of the bitumen 
that occurred early in the spring before top-dressing could be applied. 
Such repairs have, however, been few, and less bitumen has been 
required than on any of the other experiments. 
EXPERIMENT No. 7 (ASPHALTIC PETROLEUM—COLD APPLICATION). 
The surface of this experiment worked into a rather objectionable 
muddy condition as soon as the winter of 1913-14 brought continued 
wet weather and frost. In the spring it ironed out and presented 
a very satisfactory appearance until about September. At this time 
numerous small weaknesses began to develop which, owing to cold 
weather, could not all be repaired before winter. Nevertheless, the 
surface has not become so muddy this winter (1914-15) as last, but 
the mud which is formed is in some spots a lighter brown color, indi- 
cating that the oil is losing its effect. This experiment is expected to 
require re-treatment at the earliest possible time in the spring, and 
may require considerable patching, as indicated by the rapidly increas- 
ing breaks in the surface during the late fall of 1914. 
TaBLE 13.— Materials and cost data for renewal treatments of experiments Nos. 2 and 3 
Rockville Pike, Maryland, 1914. 
Experi- 
Experiment No. 2. ment 
No. 3. 
b Torpedo 
Trap. Gravel. sand! 
OG VE UW Os sees ODEO Aes cosas ee aCe plc Ne os Aarae a Ost apes Sem feet. -|4, 330 3, 650 7,460 
INTO So Be a SEC 6 ae OIG PIG AA RPE ROE ERP FE tira Ce Ea era square yards..|/7,216.6 [5,083.4 12,333 
Bituminous material, persquare yard.............-.-.-0-------- galions. - . 294 . 294 .176 
Covering material, perisquare yard-:......-......-.-.52+--. cubic yards.. - 012 . 012 . 009 
Cost (cents per square yard): 
SMC E DUNNE SUI ACO PE ieee ee ee ete, BRE. al Bes at dete ce NL @) @) 0. 048 
ipipmimanous materialise Seeker ee ee Sg he ee oe ke 2. 79 2.79 1. 234 
AM plyine bipumuunousmatenial seals. sees komt uccw (Sk ad ae (2) . 393 
Covemme materiale. cma ue ee ce omen enpe icie mee enecty wy Ae aes an a 4,39 2, 52 1. 994 
Spreadinecoveriiemiateriaih=. eos wale Ties Vek Se Oe 563 53 197 
TBA 5 SCS a Ste Peis: ee pea fers ARS pea pe Oe RR ean Se Ue tal 5, 84 3. 866 
1 Automobile distributor used; sweeping and applying included in cost of material. 
A traffic census on the Rockville Pike is taken every 13 days for a 
24-hour period. A tabulation of the maximum and average of each 
class of traffic for the period between January 1, 1914, and January 1, 
1915, is given in Table 14. 
