2 BULLETIN 407, TJ. S. DEPARTMENT OF AGRICULTURE. 
plain macadam with bituminous surface treatments, and bituminous 
concrete. Supplementary reports, describing the progress of experi- 
ments previously reported, follow the reports of the new experiments. 
EXPERIMENTS ON MOUNT VERNON AVENUE ROAD, ALEXANDRIA 
COUNTY, VIRGINIA. 
BITUMINOUS MACADAM (PENETRATION AND MDITNG METHOD) , BITUMINOUS GRAVEL 
CONCRETE. 
This experimental project is located in general upon the Mount 
Vernon Avenue Road, in Alexandria County, Va. The entire project 
deals with the bituminous type of road construction. It begins at the 
Military Road, near the Arlington Cemetery, and extends on a new 
location to McKinley Street. Passing through McKinley Street to 
Columbia Pike, the road then follows a new location to the top of the 
hill near station 37+00, where it joins Mount Vernon Avenue. The 
old location of Mount Vernon Avenue is left again at station 85+00, 
and a new location is followed across Four Mile Run to Mount Vernon 
Avenue at approximately station 131+00. From there the road 
continues along Mount Vernon Avenue to Washington Avenue, 
thence through Washington Avenue and Washington Street to the 
city line of Alexandria. The total length of the project is 23,711 
feet, or approximately 4.5 miles, and is divided into 20 experiments, 
as shown in Table 1. The experiments are numbered consecutively 
from the north end of the project toward Alexandria, and the experi- 
ments numbered 9 and 12 are identical in the construction methods 
employed. 
The project naturally falls into three sections, according to the 
nature of the construction of the road base. Section I extends from 
the north end of the project (station — 1+61) to station 153+00 at 
Hume, where the road crosses the tracks of the Washing ton- Virginia 
Railroad. A gravel base was laid throughout this entire section, 
both on the new location and on the old road, which was of earth and 
badly-worn gravel. Section II extends from station 153+50 to 
station 192+00. The base on this section is an old bituminous- 
macadam surface scarified and reshaped. Section III extends from 
station 192+00 to station 235+50, and the base is an old water- 
bound macadam surface, scarified and reshaped. 
