WHEELED VEHICLES 201 
the longitudinal stringer road, but provides a better traction 
surface. Guard rails may be placed either inside or outside of 
the stringers, except on curves of 10 degrees or more when they 
arc placed on both sides. The inside tread gauge both of the front 
and rear wheels is the same, which is not tnie of the outside meas- 
urements of front and rear tires. For this r(\ason, inside guard 
rails are preferred since trucks stoov more readily and trailers 
follow more easily. Inside guard rails should be not less than 4 
inches in height but must not be so high that they interfere with 
the brake drums or driving gear. The guard rails are made from 
small poles spiked l)oth to the crossties and to the stringers and 
when inside ones are used they are braced by small poles which 
are placed between them, about three to a pole length. Roads 
of this character should have the stumps removed from the right- 
of-way and have a 12-foot crown, ditched on both sides, and if 
necessary in the center, water from the latter being drawn away 
at least every 50 feet. Such a road requires from 80,000 to 100,000 
board feet of stringers per mile, 11,000 linear feet of 8-inch poles 
for guard rails, 2300 linear feet of 6-inch poles for cross braces, 
and about 2000 pounds of spikes and drift bolts. 
The maintenance cost of such a road is about one-half that 
for a logging railroad. 
Several forms of pole roads have been used, among them 
small hewn poles called puncheons placed crosswise; two or three 
small hewed poles laid lengthwise without crossties; and the 
so-called fore-and-aft road which has a surface made from 
hewed stringers placed on crossties. The last type is the most 
satisfactory, the puncheon road having too much vibration and 
the small pole road providing an irregular surface. 
The fore-and-aft road may have the traction surface under each 
wheel made from a single large pole, with a hewed face having a 
flat surface of 16 or more inches, or it may be made from two or 
three smaller poles, the timbers in all cases being supported on 
crossties. The single pole road is considered superior to the 
two- or three-pole one unless the faces of the poles are hewed 
so that they fit closely together because the weight of the load 
comes on the inside edges of the poles, and has a tendency to cause 
them to turn downward, thus loosening the spikes and spreading 
the poles. There also is a loss in traction surface on the two- 
and three-pole road due to the space between the timbers. Un- 
