ELASTICITY OF SUBSTITUTIONAmtrak's westbound Empire Builder derailed outside Chicago's Union Station last week account a combination of worn wheel flanges and worn track switches. "Neither the slightly worn switch point nor the worn wheel flange were in a condition that made them non-compliant," according to Warren Flatau of the Federal Railroad Administration [Editorial note. I am quoting from page 1, section 2 of the DuPage edition of the Chicago Tribune. The Tribune's web site has intrusive registration procedures and the Federal Railroad Administration's is as convoluted as the approach to London King's Cross.] Amtrak, the owner of the Chicago trackage, has completed removal of the track switches and reprofiled the track. As one cannot remove all track switches and keep the railroad fluid, railroads must strike a balance between maintaining switches and maintaining wheels. There are evidently allocations of resources among these tasks that raise the likelihood of derailments.