WHEELED VEHICLES 203 
public roads in Washington will bo rcstrictod to from 2400 to 3000 
board feet, depending on locality. TIk; average loading time 
ranges from 10 to 15 minutes, the unloading time 10 minutes, 
and the average time re(}uired per mile, 10 minutes. The time 
required for a round trip on a haul of 1 mile, therefore, is from 30 
to 35 minutes. 
BIBLIOGRAPHICAL NOTE TO CHAPTER XII 
Drissen, J. P.: Time Study of Motor Truck Logging of YeUow Pine. 
The Timberman, August, 1921, p. 97. 
Knapp, F. M.: Motor Truck Logging Methods. Bui. No. 12, Univ. of 
Washington, Engineering Experiment Station, Seattle, April, 1921. 
Mason, Fred R. : Study of Daily Production of Big Wheels. The Timber- 
man, April, 1921, p. 39. 
Meiklejohn, E. N.: Truck Logging. The Timberman, Oct. 1920, pp. 
85 and 86. 
Van Orsdel. John P. : Plans for Motor Truck Logging. The Timberman, 
July, 1921, pp. 97, 100, and 102. 
