75 



The effect of wood preservation upon the requirements of Illinois 

 railroads for tie timber is twofold. It greatly increases the potential 

 supplj' from all, and especially from local, sources, and it cuts the re- 

 quirements for renewals nearly in half, thus improving the position of 

 the roads from 300 to 400 per cent and postponing the day when the 

 roads will be forced to introduce other materials in place of wood for 

 ties. 



The rate of annual renewals is the gage of the length of service of 

 the average cross-tie. For main tracks the number of ties per rail of 

 33 feet averages 20, giving 3200 per mile, while on side-tracks it runs 18, 

 or 2880 per mile. An average for all track and roads is sometimes 

 taken as 3,000 ties per mile. The annual replacements per mile, divided 

 into this figure, represent the life of the average tie with approximate 

 accuracy after the initial period following construction has elapsed. As 

 new construction has been practically at a standstill since 1915, this 

 figure should gage the future requirements of Illinois roads for tie 

 timber. 



Figures for the years 1917-21 inclusive give for all Class I rail- 

 roads of the United States an average annual renewal of 235 ties per 

 mile. This is equivalent to a life of 12^ years, which indicates, first, 

 the extent to which the more durable woods have in the past been pre- 

 ferred and. second, the transition which is rapidly taking effect. The 

 roads simply could not afford to use ties whose service fell much below 

 10 years, and made the shift as soon as economic necessity compelled 

 action. 



The annual requirements of Illinois roads for replacements are 

 slightly more than this average, being 241.0 ties per mile for re])!ace- 

 ments alone, and 245.9 per mile when new construction is included. It 

 will require probably ten years to reduce this figure to 174 ties ])er mile 

 for all tracks, which is the goal set for 100 per cent use of treated 

 cross-ties. Should the mileage of track remain fairly stable at 25,000 

 miles, this would require 4,350,000 ties annually. Allowing an increase 

 in trackage of 10 per cent and a further increase in renewals due to 

 heavier traffic of 20 per cent upon the ultimate mileage, the number re- 

 quired would be 5,742,000 ties annually. 



Unless unforeseen factors arise it appears safe to estimate that a 

 permanent supply of 6,000,000 ties for steam roads alone should guar- 

 antee the continuous use of wood for cross-ties in Illinois. 



