[Title 49, Volume 4]
[Revised as of October 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR236]
[Page 485-521]
TITLE 49--TRANSPORTATION
CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
PART 236--RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES
Sec. 236.0 Applicability, minimum requirements, and civil penalties.
( a ) Except as provided in paragraph ( b ) of this section, this part applies to railroads that operate on standard gage track which is part of the general railroad system of transportation.
( b ) This part does not apply to rail rapid transit operations conducted over track that is used exclusively for that purpose and that is not part of the general system of railroad transportation.
( c ) Where a passenger train is operated at a speed of 60 or more miles per hour, or a freight train is operated at a speed of 50 or more miles per hour, a block signal system complying with the provisions of this part shall be installed or a manual block system shall be placed permanently in effect which shall conform to the following conditions:
(1) A passenger train shall not be admitted to a block occupied by another train except under flag protection;
(2) No train shall be admitted to a block occupied by a passenger train except under flag protection;
(3) No train shall be admitted to a block occupied by an opposing train except under flag protection; and
(4) A freight train, including a work train, may be authorized to follow a freight train, including a work train, into a block but the following train must proceed prepared to stop within one-half the range of vision but not exceeding 20 miles per hour.
( d ) Where any train is operated at a speed of 80 or more miles per hour, an automatic cab signal, automatic train stop or automatic train control system complying with the provisions of this part shall be installed.
( e ) Nothing in this section authorizes the discontinuance of a block signal system, interlocking, traffic control system, automatic train stop, train control, or cab signal system without approval of the Federal Railroad Administration.
Note item ( d ): The statement is "80 mph or more" Therefore, you cannot have a speed limit of 80 mph without an expensive set of extra lights, bells, and whistles. A lot of railroads traditionally had passenger train speed limits of 70 mph, 75 mph, and 80 mph. Since the track safety standards have no intermendiate break for passenger train speed limits between 60 mph and 80 mph, anybody wanting to run something faster than 60 mph had to maintain the tracks to pass the 80 mph standard. Well, you can't set a speed limit of 80 mph without a lot of extra signal hardware that few railroads with signals used. Hence, all the 79 mph stuff out there.
Go back up to item ( c ), and you will see why there is also a lot of 59P/49F territory out there. Don't know what the percentage is now since so many lightly trafficed lines have been abandoned in the last few years, but at least fairly recently only about 1/3 of the American railroad system route milage had any form of signals at all. Therefore, the maximum speed you could have would be 59 mph for passenger trains and 49 mph for freight trains. There are still some passenger trains on non-signaled tracks. The Vermonter north of White River Junction is one. If it should ever come back the Sunset Limited eastern part between Flomaton Alabama and Tallahassee Florida was another.
Some railroads were a little more conservative. For example: Kansas City Southern set their passenger trains speeds at 78 mph after the rule came into effect. The GM&O southern lines dropped their speed limit from 60 mph to 55 mph. That they were running on 90 lb/yd jointed rail may have also had something to do with it. But then, maybe not. At least up until the late 40's early 50's, the Twin Star Rocket and Sam Houston Zephyr were allowed 90 mph between Waxahatchie Texas and Houston on unsignaled track with 90 lb/yd jointed rail. I had heard once that the ride quality on this line was somewhat exciting.