The NKP line is too far north to be a viable alternate route for this traffic. It also carries mostly high-speed traffic - 60 mph double stacks and road railers. The NKP is single track CTC with passing sidings and currently sees 30+ trains per day.
Operationally it makes no sense to put speed restricted, 40 mph traffic on a single-track line that is already carrying mostly high speed traffic. It would just serve to slow the high speed trains down to 40 mph...not at all what they want to do.
By using the former P Company line for the speed-restricted traffic, all the "slow" traffic will be on that line from Alliance, Ohio to Chicago. That leaves the NKP and everything west of Alliance on the C&P and the ex-NYC Water Level Route free for the high speed traffic.
East of Alliance, the former PRR is all double and even some triple track, giving the Pittsburgh East Dispatcher a bit more flexibility in how he runs the railroad with a "fast-slow" traffic mix. East of Pittsburgh, the slow traffic will likely take the Conemaugh line between Pittsburgh and Johnstown, leaving the Pittsburgh line free for the high-speed traffic.
