DUST PEEVEFTION" AND ROAD PRESERVATION, 1915. 65 



A traffic census is taken every 13 days for a 16-h,oiir 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 only. 



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 pubhshed in Circular 

 No. 98, and reports of annual inspections and repairs are given in 

 Circular No. 99, Office of PubUc 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 shght 

 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 som(!what 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 crumbhng.' 



