The decline in coal traffic this year is having the salutary effect of improving overall service on freight railroads in North America, according to Larry Gross, a senior consultant for Indianapolis-based econometrics firm FTR Associates. Railroads are running about 8 percent faster than in 2011 because there are fewer unit coal trains on the system. As reported last week , utilities are turning to cheaper natural gas as a substitute for coal. A mild winter, large utility stockpile...