DUST PREVENTION AND ROAD PRESERVATION, 1915. 65 
A traffic census is taken every 13 days for a 16-hour period. A 
tabulation of the maximum and average of each class of traffic for the 
period between March 8, 1915, and February 22, 1916, is the same as 
that taken for the 1912 Chevy Chase experiments. Each side of the 
road carried traffic in one direction oDly. 
SUPPLEMENTARY REPORT OF EXPERIMENTS MADE AT JAMAICA, N. Y., 
1911. 
OIL-CEMENT CONCRETE, OIL-ASPHALT, TAR, AND FLUXED NATIVE ASPHALT. 
The original report of these experiments was published in Circular 
No. 98, and reports of annual inspections and repairs are given in 
Circular No. 99, Office of Public Roads, and in U. S. Department of 
Agriculture Bulletins Nos. 105 and 257. The following report relates 
to the condition of the pavement on January 22, 1916. 
Experiment No. 1. — Oil-Cement Concrete. 
The bituminous surface treatment is worn away to a very con- 
siderable extent. At present the concrete is exposed in many large 
and small patches, and is generally somewhat worn and potted, 
especially at the street intersection. 
Experiment No. 2. — Cut-back Oil-Asphalt, Mixing Method. 
This experiment will not be reported on again, excepting for the 
easterly 50 feet. It was entirely scarified in October, 1915, with the 
exception of the easterly 50 feet, shaped and rolled, and then surfaced 
with 2 inches of asphaltic concrete prepared according to the Topeka 
specification. The easterly 50 feet is still in fair condition in the 
center, but is somewhat wavy along the sides. 
Experiment No. 3. — Fluxed Native Asphalt, Mixing Method. 
This section is in practically the same condition as indicated in 
the last inspection report. The waves along the north side for the 
easterly 30 feet have become somewhat deeper and there is a slight 
waviness appearing along both sides throughout the entire length of 
the section. 
Experiment No. 4. — Refined Coal Tar, Mixing Method. 
This section is in good condition for a width of about 15 feet along 
the center. It has become somewhat wavy along both sides through- 
out its entire length. On the south side from station 10 + 68 to the 
east end of the section for a width of about 5 feet, where the seal coat 
was worn off last year, the pavement is now crumbling. 
