Slavery and Confederate Railroads

How essential were slaves to the Confederate railroads?

   Slaves were required by Confederate railroad construction (i.e. the Piedmont Railroad and others) because of the great scarcity of white labor in the South throughout the war. You cannot read the historical record without being struck by the number of times writers complain of a shortage of manpower for the army, industry, railroads, food production, etc. Slaves filled in for the missing whites in railroad construction.
   Likewise, slaves filled in for missing whites in track maintenance and the menial train jobs (brakeman, fireman, station labor). In late 1864, the Atlantic & Gulf RR reported 350 slaves working on the track, as train hands and in warehouses.
   In construction, track maintenance and train labor, slaves had been the normal labor force before the war. 

What would have been the effect of the South not being able to use slaves for these railroads jobs? 

   Given the resistance of the army commanders to detailing men to any non-military job, the railroads would have deteriorated faster than they did and the construction of the essential railroads that was undertaken would probably not have been completed. The result of these two would probably have been the shortening of the war by something like 6 months.
Here are the links to slave-related pages.
AHC, A&M 1-1-62 A typical slave hire contract for one year
AHC, S&M 1-14-65  A typical slave hire contract for one year
NA, LS 10-31L-62 Slaves used in the CS Locomotive Shop
Central (of Georgia) buying slaves
Charlotte & South Carolina Slaves
North Carolina Slaves Hired 1862
North Carolina Slaves Hired 1864
Richmond & Petersburg Slaves
South Carolina Slaves
Virginia & Tennessee Employees
Virginia Central Employees