In 1947, the Interstate Commerce Commission issued an order establishing a federal speed limit of 79 mph, on all rail lines not equipped with Automatic Train Stop (ATS) or Automatic Train Control (ATC). Equipment designed to automatically stop a train if the engineer ignores a warning signal. To this date, that order has an impact on the speeds of Amtrak passenger trains.
ATS/ATC Further Explained
In 1922 and 1924, as these technologies were being developed, the Interstate Commerce Commission ordered most railroads to equip first one subdivision or district, and then a second subdivision or district, with ATS or ATC. Many railroads actually went beyond this order, and equipped most of their signaled main lines with such systems.
For the railroads not extensively equipped with these systems, they were affected the most by the 1947 order. Unless all of their speed limits were below 79 mph anyway. Some affected railroads installed such systems over additional lines. While many railroads actually simply lowered their speed limits to 79 mph.
And during the 1960's and 1970's, most of the railroads actually ELIMINATED these ATS and ATC systems, cutting costs. Most of the remaining systems in the Midwest are on Metra lines. But speed limits on these lines are never above 79 mph.
Included here are links to scanned images from various railroad employee timetables, showing the higher speed limits once in effect on some of these lines in the Midwest. Slower Amtrak trains now might be discouraging. But one promising sign now, is the development of high speed service from Chicago to Detroit and St. Louis. Lines which during the golden age actually never had service above 80 mph.
New York Central
Most main lines were equipped with ATS, until 1971 when the bankrupt Penn Central deactivated it all.
New York Central/Michigan Central
On this developing high speed route to Detroit, speed limit was never more than 80 mph during the golden age of passenger trains, even with ATS. Speed limits were lowered over the deteriorating route by 1971, when the bankrupt Penn Central deactivated the ATS. In the late 1970's, Amtrak had the segment it owns west of Kalamazoo back up to 79 mph.
In 1953, ATC was installed between Chicago through Aurora to Savanna, in compliance with the 1947 order. Proposals existed to extend ATC from Aurora to Mt. Pleasant IA, and from Savanna almost to St. Paul. But that was never done. The 1971 formation of Amtrak resulted in the elimination of passenger service to St. Paul, and deactivation of the ATC west of Aurora. ATC remains in use between Chicago and Aurora for commuter trains.
ATC existed over most of the route between Chicago and St. Paul, until around 1970.
Chicago & North Western
In 1952, ATS was installed from Chicago through Milwaukee to Wyeville WI, in compliance with the 1947 order. Different from the ATC system which had existed since the 1920's from Chicago to Omaha. ATS was also installed from Chicago to Harvard in 1966 and 1967. Those ATS installations, along with the ATC installation west of Chicago, continue to exist on the lines used by Metra.
New York Central/Big Four
Southeast of Kankakee, on the route used by the James Whitcomb Riley.
South of Logansport through Indianapolis to Louisville, on the route used by the South Wind.
Between Pequot (near Coal City) and Fort Madison, ATC without wayside signals was installed in 1925, in compliance with the 1922 and 1924 orders. In the 1950's, ATS was installed on most of the Santa Fe passenger lines west of Fort Madison, to Kansas City and beyond. East of Fort Madison, the ATC system was deactivated in favor of wayside signals in 1970, the line remaining double track with CTC. While ATS remains in use west of Fort Madison, enabling Amtrak's Southwest Chief to continue to operate at 90 mph.