ACL Signalling Practices: Automatic vs. "Non-automatic" Interlockingsgreenspun.com : LUSENET : ACL and SAL Railroads Historical Society : One Thread
I am hoping that there is someone out there who can provide some much needed information on ACL signaling practices regarding interlockings with other railroads. My main areas of research are the ACL's Meggetts Branch and the SAL's EC mainline, both of which served a major truck farming region south of Charleston SC. A review of a 1939 ACL Employee timetable shows that the ACL's Meggetts Branch and associated Hollywood Spur crossed the SAL's EC mainline four times. I am in need of information regarding how these interlockings would have been signaled circa 1940 (nothing remains today).
The instruction section of the ACL timetable indicates the crossing between the ACL branchline and the SAL mainline was an automatic interlocking. As a kid I recall seeing a searchlight signal on the ACL branch that was located approximately 0.5 mile from the ACL/SAL crossing and always displayed a red or stop indication. (The 0.5 mile signal location from the crossing seems rather far considering the 20 mph speed limit on the ACL branchline). Despite being an "automatic" interlocking, per timetable instructions the ACL crew had to open the control case, turn a knob-hold it for a couple of seconds, release, and quickly close the control box and hope for a procede signal before they could cross the SAL mainline. I am assuming the "automatic" in this interlocking means that once the ACL train cleared the circuit, the signal indications would automatically revert back to stop=ACL and procede=SAL. Can someone confirm if this interpretation is correct?
The greater source of confusion regards the three interlockings at the locations where the ACL's Hollywood Spur crossed the SAL mainline-the timetable makes no mention of signals, etc. Can anyone familiar with the ACL & SAL suggest how these "non-automatic" interlockings would have been signaled-if at all? At first glance, the use of a swinging smashboard seems dangerous considering the train speeds on the SAL EC mainline vs the 15 mph speed limit on the ACL spur. Thanks in advance for any feedback and suggestions.
-- Buddy Hill (PalmettoLTD@hotmail.com), December 29, 2000
Looking at a 1939 SAL ETT (also supplied by Cliff Kendall)there is mention of gates at railroad crossings. The SAL says the following: Where railroad crossings are protected by gates, set normally clear for SAL Ry, trains will approach under control prepared to stop short of crossing or derails and will proceed if crossing is seen to be clear and gates are set against foreign railroad.
Where railroad crossings are protected by gates set normally against SAL Ry., trains will stop short of crossing or derails and if crossing is seen to be clear and no approaching conflicting movement is observed,member of crew will set gates against foreign railroad and clear for SAL ry.
Gates operated by trainmen must be restored to normal position after movement has been completed. If derails are connected to gates, trainman operating gates must assure himself that the train has cleared the derails before restoring gates to normal position.
Where railroad crossings are protected by gates operatedby watchman, trains will approach crossing, under control, prepared to stop short of crossing or derails, and if crossing is seen to be clear, and gates are set against foreign railroad and clear for SAL Ry., will proceed.
The same ETT listed maximum speeds through semi-automatic grade crossings at "Rockets" MP 0.06 Southern Rwy at 15 mph and at "LaCrosse" MP 78.9 Southern Rwy at 35 mph, attended interlocking signalled "Edgeton" MP 154.7 Norfolk Southern Rwy at 45 mph, attended interlocking signalled "Shops" MP 2.1 Norfolk and Portsmouth Belt Line Rwy. , automatic unattended interlocking "Algren" MP 9.4 Virginian Rwy., both by special rules which required the crews to proceed on signal indications, being prepared to stop. If the distant signal was a fixed signal, speed limits were set by ICC order to 20 mph.
-- Michael W. Savchak (Savchak @MNR.org), January 08, 2001.
Buddy-I went home and found a copy of a 1944 ACL ETT(kindly sent to me by Cliff Kendall) and found the following:
Automatic Interlockings Trains will approach interlocking expecting to find a stop signal. When train is stopped at a stop signal,and finds no conflicting train movementis evident within signal limits, movement over the crossing may be made as follows:
First: After trainman positively assures himself that no train is approaching on the crossing line he will- Second: Unlock and open the small door marked ACL located on upper portion of instrument case(at crossing) and locked with a standard ACL switch lock, which will expose the black knob of a release. He will then turn the black knob to the right until it comes to a stop, and then release it, immediately closing and locking the door. After a time interval of two minutes, the signal should indicate proceed. Third:In case the signal does not indicate proceed, after two minutes, train movement over crossing may be made only under flag protection. Fourth: Prompt report must be made to the dispatcher when necessary to use the release.
The SAL had a similar rule for the release function.
This release fuction was to be used only if the interlocking appeared to be malfunctioning-as an example if there was a power failure. Normal operations would have the home signal at stop only if there was a train in the limits of the crossing on the opposing line, since the circuitry was set up for "first come-first serve".
At Dupont, Heath, Parrishville and Barrelville, on the Charleston District, position of the crossing signal was normally clear for the SAL and normally stop for the ACL. ACL crews would then operate the interlocking.
Meggetts was listed as an automatic crossing by the ACL and had a 20 mph speed restriction.
Lemme know if you want a copy.
I do not have a copy of a SAL ETT for the Charleston District, but one for the Richmond district has similar instructions.
-- Michael W. Savchak (Savchak @MNR.org), January 08, 2001.
Doug/Micheal - Thank you for describing how these interlockings would have worked. I do have a follow-up question to anyone possessing a 1939-early 40's SAL employee time table for this section of the SAL (Charleston to Savannah). Could you please provide the SAL's description of the automatic interlocking at Meggetts SC, and the non- automatic interlockings at Barrelville,SC, Parrishville, SC, and Heath SC. Thanks.
-- Buddy Hill (palmettoLTD@hotmail.com), January 03, 2001.
To add on to Doug Riddle's answers, speed limits at grade crossings are mandated by an ICC order dated September 1, 1939. This order states that at any grade crossing which has a fixed signal-i.e. if it is not an automatic grade crossing, the maximum speed limit approaching the grade crossing is 20 mile per hour. A true automatic grade crossing without the 20 mile per hour speed restriction would have to have an automatic, operable, distant signal, as well as an operable home signal at the grade crossing it self. Typically on mainlines, the signal system for the main line provided protection for the main line, while the branch line was provided with either a fixed distant and home signal, in which case the speed limit on the branch line was fixed at no more than 20 mph, or it had a short track circuited length with an operable distant and home signal.
Such a crossing figured in an accident on December 19, 1940 at Zephyrhills Fla. where a Seaboard passenger train struck the side of an ACL freight. The grade crossing was an automatic one, namely, there were track circuits on both lines for this grade crossing only, as at that time, the SAL line was operated by a manual block system, and timetable and train orders, while the ACL line was timetable and train orders only. The grade crossing was on a first come-first serve basis, both lines having fixed distant signals. The speeed limit on the ACL was 20 mph, while on the SAL, it was 60 mph. The circuitry at the interlocking works on the basis of the first train arriving at the approach circuits establishing the priority. If both trains arrive at the circuits simultaneously, then all home signals stay in the stopped position.
In this case, the SAL train, number 305, engine 824, a passenger baggage car, a coach, a coach-diner and two sleepers, approached the distant signal at a speed of 15 miles per hour. The engineman noted that the home signal cleared to proceed and he then accelerated the train. At a speed of 30-35 miles per hour,the SAL train struck the side of ACL freight 213. The freight, consisting of engine 1656, 44 cars and a caboose, entered the grade crossing after the SAL train entered the circuit, and was struck on the side of the first car. The engineman of the SAL train was killed and 19 were injured.
The ACL engineman claimed that he made a brake application as the train entered the track circuit, and he saw the home signal as proceed. The signal was then obscured by smoke from his engine and when the smoke cleared, the signal was at stop. He claimed that he had insufficient air to stop before the home signal. The ICC felt that the ACL crew was at fault as it was clear that they had entered the approach circuit after the SAL train had received a proceed. The ACL train's greater average speed, and the fact that the ACL had a shorter approach circuit distance were the key factors in the ACL train being at the crossing first. The ICC also faulted the SAL since they had a fixed distant signal and permitted their trains to approach the home signal at a speed of 60 mph. The ICC had directed all railroad the previous September to reduce the speed limits of all approach circuits to automatic grade crossings to 20 mph wherever the distant signal was fixed. Had the SAL train been limited to 20 mph, the train would have been able to stop in time to avoid the ACL train.
-- Michael W. Savchak (Savchak @MNR.org), January 02, 2001.
Automatic Interlockings are those where there are signal circuits for both intersecting lines in both directions of travel. We often refer to them as "First come, first serve". The first train to activate the circuit receives a favorable signal AFTER the electronic circuitry searches the intersecting line and confirms that there is no opposing movement. This is why it is called an "automatic" interlocking. Even on a dispatcher controlled railroad, an Automatic Interlocking is independant. Now, there may be timetable special instructions notifying trains of the same or different railroad at the intersection to contact the dispatcher before fouling the circuit, but the signal is activated by the presence of a train on the circuit. As for the crew going to the signal house and turning a switch: If you are unable to obtain a signal, there are sometimes manual time-releases as a backup, which should produce the desired results if there is no conflicting movement. On lighter sections of the railroad, railroad crossings at grade are protected with simple "stop" signs, gates, or signals. In the employee timetable for each subdivision, there is a section which identifies junctions and railroad crossings at grade and details how they are protected and which line the route is normally lined for. You would have to have a copy of either an ACL or SAL timetable for the period for which you wish to investigate to know which method was used. I hope this helps.
-- Doug Riddell (email@example.com), December 31, 2000.