﻿ROAD 
  CONSTRUCTION 
  97 
  

  

  is 
  also 
  clear 
  that 
  for 
  many 
  centuries 
  to 
  come, 
  large 
  areas 
  of 
  our 
  country 
  

   can 
  hope 
  for 
  nothing 
  better 
  than 
  good 
  natural 
  roads. 
  

  

  The 
  faults 
  of 
  our 
  natural 
  roads 
  which 
  could 
  easily 
  be 
  remedied 
  are 
  

   mainly 
  these 
  : 
  

  

  1 
  The 
  roads 
  are 
  too 
  narrow 
  and 
  too 
  high 
  in 
  the 
  center, 
  and 
  on 
  account 
  

   of 
  their 
  narrowness 
  the 
  wheels 
  all 
  run 
  in 
  the 
  same 
  track 
  and 
  the 
  extreme 
  

   curvature 
  of 
  the 
  road 
  bed 
  compels 
  the 
  wheels 
  to 
  run 
  on 
  the 
  edge 
  instead 
  

   of 
  the 
  surface 
  of 
  the 
  tires, 
  the 
  combination 
  of 
  the 
  two 
  faults 
  causing 
  the 
  

   formation 
  of 
  deep 
  ruts 
  ; 
  

  

  2 
  Loose 
  stones 
  are 
  allowed 
  to 
  remain 
  in 
  the 
  roads 
  and 
  the 
  work 
  of 
  

   repair 
  is 
  not 
  directed 
  toward 
  keeping 
  the 
  surface 
  smooth 
  ; 
  

  

  3 
  Insufficient 
  attention 
  is 
  given 
  to 
  the 
  construction 
  of 
  drains 
  and 
  

   culverts. 
  

  

  Road 
  Construction 
  

  

  The 
  experience 
  of 
  over 
  2,000 
  years 
  has 
  shown 
  conclusively 
  that 
  there 
  

   are 
  two 
  essential 
  points 
  to 
  be 
  aimed 
  at 
  in 
  the 
  construction 
  of 
  a 
  perfect 
  

   road 
  ; 
  

  

  1 
  A 
  hard, 
  smooth, 
  waterproof 
  surface 
  ; 
  

  

  2 
  A 
  thoroughly 
  dry 
  foundation. 
  

  

  These 
  principles 
  were 
  known 
  to 
  the 
  Romans 
  three 
  hundred 
  years 
  

   before 
  Christ 
  and 
  used 
  in 
  the 
  construction 
  of 
  their 
  best 
  highways. 
  

  

  The 
  surface 
  of 
  a 
  good 
  road 
  must 
  be 
  of 
  sufficient 
  strength 
  to 
  resist 
  the 
  

   wear 
  and 
  tear 
  of 
  traffic, 
  and 
  smooth 
  enough 
  to 
  prevent 
  undue 
  strain 
  and 
  

   wear 
  on 
  vehicles. 
  In 
  connection 
  with 
  this 
  the 
  soil 
  beneath 
  must 
  be 
  made 
  

   dry 
  and 
  kept 
  dry. 
  Therefore 
  the 
  subject 
  of 
  road 
  drainage 
  is 
  as 
  important 
  

   as 
  that 
  of 
  road 
  metaUing. 
  

  

  The 
  best 
  road 
  covering 
  is 
  composed 
  of 
  angular 
  fragments 
  of 
  some 
  

   stone 
  which 
  will 
  grind 
  on 
  the 
  surface 
  into 
  a 
  dust, 
  which 
  when 
  wet 
  will 
  

   bind 
  or 
  in 
  a 
  measure 
  cement 
  the 
  fragments 
  together, 
  so 
  that 
  water 
  will 
  

   not 
  penetrate. 
  The 
  angular 
  form 
  is 
  essential 
  to 
  make 
  the 
  fragments 
  

   interlock. 
  The 
  sizes 
  should 
  be 
  quite 
  uniform, 
  except 
  that 
  the 
  surface 
  

   layer 
  may 
  consist 
  of 
  fragments 
  different 
  in 
  size 
  from 
  those 
  in 
  the 
  bottom 
  

   course. 
  

  

  The 
  total 
  thickness 
  of 
  this 
  metalling 
  must 
  be 
  at 
  least 
  six 
  inches 
  on 
  a 
  

   natural 
  soil 
  foundation. 
  The 
  fragments 
  should 
  not 
  exceed 
  two 
  and 
  a 
  

   half 
  inches 
  in 
  diameter, 
  and 
  should 
  be 
  rolled 
  in 
  two 
  separate 
  courses 
  

   with 
  a 
  heavy 
  steam 
  roller 
  until 
  the 
  surface 
  is 
  absolutely 
  firm. 
  This 
  is 
  

   the 
  Macadam 
  system. 
  

  

  