SCIENCE AND INDUSTRY. 
until he has thoroughly instructed the local officer. Experts are also 
sent out, on request, to study the whole system of roads in a local 
district, and to formulate a plan of action for their improvement. 
Standard plans and specifications for bridges and other structures are 
prepared in the office and furnished to local authorities. 
(c¢) Koad Materials, Test, and Research.—This branch carries out 
investigations of road-building rocks, dust preventives, and road binders. 
Routine tests are carried out free of charge when submitted by State 
and local government officials, or by good-roads organizations. 
(d) Field Experiments—Experiments are carried out to determine 
the relative merits of various materials, and of the various methods and 
types of road construction and maintenance. <A section of road is 
selected, and co-operative arrangements are entered into with local 
authorities. The Office of Public Roads retains the right to carry out 
the experiments. Short sections of road are constructed, extending 
over the entire length selected, each section being an experiment in 
itself, designed to determine the relative merits of certain road materials 
and the best methods of using them. Systematic inspections are made 
periodically. Field experiments are also carried out to determine the 
effect of width of tire, diameter of wheel, type and size of axle bearing, 
and power required to haul vehicles of different types over various 
classes of road surfaces. 
Researcu Worx ar tHe Narronat Puystcar. Lasorarory, Enauanp. 
A special laboratory for testing road materials and methods of 
construction has been established at the National Physical Laboratory 
under the auspices of the Road Board. There is a complete installation 
for testing road materials, such as stone, for resistance to impact, 
- abrasion, &c.; but the most important part of the installation is the 
“road-testing machine.” This is an arrangement whereby an actual 
experimental road can be tested to destruction under what may be 
described as intensified traffic conditions. The road to be tested is laid 
down in the form of a circular track, 2 feet wide and 30 feet in 
diameter—the foundation of the road is provided in the shape of a ~ 
concrete channel, in which ithe bituminous or other road material can 
be laid under excellent conditions. On the experimental road or track 
thus constructed eight heavy steel-shod wheels are run, generally at a 
speed of 8 miles per hour, and each wheel is separately loaded and 
driven, so that the wheel does not merely run on the road, but transmits 
to it driving stresses such as occur in practice. The conditions are, 
in fact, very similar to those which exist on a modern road under heavy 
traffic, but the wear of the road is accelerated owing to the fact that 
the artificial traffic is much more concentrated and continuous than it 
would be in actual practice. It has been found experimentally that 
few roads can resist the wear of this testing machine for more than 
a few days, particularly when the surface is kept wetted. Information 
as to the relative wearing properties of roads constructed with different 
materials or on different methods can thus be obtained much more 
rapidly, and under much more definite conditions, and at smaller cost, 
than by experiments on actual roads. 
106 
