AF Tower

Alexandria & Fredericksburg Junction

Richmond, Fredericksburg & Potomac Railroad (RF&P) - Milepost 104.3 Alexandria, Virginia


Herewith is submitted the Ninetieth Annual Report of the operations of your Company, for fiscal year ended December 31, 1921.

The fractional decrease in second track mileage, shown in the Mileage Statement, on page 8, is due to change of location of junction of freight tracks forming the connecting link with Potomac Yard southwardly with the main line tracks at "A. F." tower interlocking, incident to the revision of track layout and installation of new interlocking plant at the latter point, hereinafter referred to in detail.


An electro-pneumatic interlocking plant with new brick tower was constructed at "A. F.," just south of Alexandria, replacing the mechanical plant and wooden tower, which had been in service since 1906, and were worn out and obsolete. A greatly improved track layout was installed at this important junction point, through which passes the entire freight traffic between the north and south, handled through the Potomac Yard gateway, as well as all north and south passenger traffic via Washington.


Source: NINETIETH ANNUAL REPORT OF THE Richmond, Fredericksburg and Potomac Railroad Company. RICHMOND, VA., March 6, 1922. Pages 1, 6.

This interlocking was in continuous service between 1904 to 1970. From establishment to 1921, a wood tower builing housed a mechanical interlocking frame. In 1921, it was replaced with a brick structure accomodating a Union Switch and Signal (US&S) electro-pneumatic interlocking machine.

AF interlocking was the junction between the RF&P and the Southern Railway's (SOU) Washington Division. It was six tracks across; from the south edge of the plant, the first three were SOU trackage: North Freight track, South Freight track, and North Passenger Track. Next came the RF&P tracks: 1, 2, and 3. A SOU South Passenger track connection, referred to as the "Horn" parted from the north side of RF&P track 3 at Seminary, .4 mile south of AF Tower. The four SOU tracks converged at SOU's CR Tower approximately 1 mile south of AF Tower, and the SOU was double track from that point to the South. ''CR'' stood for Cameron Run, a creek that passes under the right-of-way at that point. Prior to a rebuilding of the RF&P which added a third track and elevated all so they could pass over the SOU North Passenger and both Freight tracks, these crossed at grade at ''VM Crossing.'' The telegraphic call sign for this location was ''AF.'' In 1904, it was at milepost 105.4.

Both SOU North Freight and South Freight tracks had set-out tracks between AF and CR. These two tracks ran East through the AF interlocking into the SOU Alexandria Yard. Alexandria Yard was essentially the end of SOU-owned trackage. From AF Tower, SOU passenger trains for Washington, DC, operated over the RF&P trackage rights to the south end of Long Bridge. From there, they ran over the Pennsylvania Railroad (PRR) to the portal of the First Street Tunnel, which provided entry to Washington Terminal. SOU freight trains bound for Potomac Yard (PY) operated within yard limits from AF Tower onto RF&P track 4; they departed PY on RF&P track 3 and return to SOU rails at AF Tower by heading onto the South Freight track. The set-out tracks allowed PY-bound freights to drop-off or pick-up a block of cars for Alexandria Yard handling. These set-out tracks were within the SOU Alexandria Yard limits, so that a switcher could run through AF interlocking between the yard and the set-out tracks without orders. Alexandria Yard serviced local industries, built local freight trains for the Harrisonburg Branch, the Warrenton Branch, and the mainline south to Monroe. Alexandria Yard also had a roundhouse and locomotive shop that serviced freight engines for both PY and Alexandria Yard freight trains. Locomotives used on PY freight trains were shuttled between Alexandria Yard and PY with a hostler engineer.

The Chesapeake and Ohio Railway (C&O) ran over the SOU on trackage rights. C&O freight trains did not enter Alexandria Yard, but passenger and freight trains otherwise operated in a similar fashion as those of the SOU.

1921 Views from US&S Presentation Album

The first view above is the tower building, which is facing south in the photo, towards RF&P and Southern Railway (SOU) tracks. In the first floor from left to right were the air compressor room, a lavatory and oil-fired furnace, storage batteries for signaling equipment, and the relay room. The second floor consisted of a single room with stairs at the rear. The operator's desk, interlocking machine, and model board were in this room. All four walls had double-sash windows.

This view is looking northward, with AF Tower to the left about 300 yards in the distance. The photographer is standing betwee RF&P tracks 2 (on left) and 1 (to right). Track 3 at the far left was primarily the southbound RF&P, SOU, and C&O passenger train track. Track 2 was used by northbound RF&P passenger trains. Finally, track 1 was primarily used by north and southbound RF&P freights between South Franconia, Virginia, and AF interlocking. This additional track between those points allowed freight trains to be ''stacked'' awaiting entry to Potomac Yards. Since there was a significant grade in both directions, it also allowed RF&P passenger trains on tracks 2 or 3 to run around freight trains. At the immediate right of the three-blade signal is the SOU North Passenger Track which joined RF&P track 1 about 200 feet ahead of the photographer's position.

Here's the US&S interlocking machine with model board above. The operators desk is to the far right corner of the scene, facing the northward windows. What is considered ''northward'' in terms of trackage is actually due east at this point. In 1922, the interlocking limits were roughly bounded by the Telegraph Road underpass on the east and Gibbon Street to the west. The model board shows the three RF&P tracks at the top and three SOU tracks at the bottom at the west end of the interlocking limits. One the east end, two passenger tracks (tracks 3 and 2) extended to the South End of Long Bridge, just beyond ''RO'' Tower. Two freight tracks (1 and 4) entered Potomac Yards (PY); the east interlocking limits were the southern end of PY yard limits. Finally, two SOU freight tracks entered Alexandria Yard, which was approximately .5 mile to the east of AF Tower.

This picture was taken from a signal bridge looking in track direction south (actual direction is west). The scene is approximately at the same point as the present Telegraph Road bridge in Alexandria, about 3/4-mile south of the Alexandria Amtrak Station, formerly Union Station. This was the northward interlocking limits in 1922 through 2001.

Several changes took place between 1921 and 1970. At some point, signal bridges and color lights replaced the semaphore signals shown in these views. Next, the power switch controller was installed for southbound SOU and C&O passenger trains to leave the RF&P track 3 at Seminary and head onto the Horn track to CR Tower. At approximately the same time, AF Tower was given the power switch controllers for South Franconia, where the interlocking consisted of track 1 joining track 2, and a dual set of crossovers between tracks 2 and 3.

In the early 1960s, the model board shown was replaced with a smaller ''NX'' style of pushbutton board. This board depicted the trackage between RO and AF interlockings, so that RO interlocking was remotely controlled from AF. At that time, the contol of South Franconia interlocking was transferred to the RF&P dispatcher's office at Richmond's Broad Street Station. Seminary interlocking, consisting of a searchlight-style dwarf home signal and an electric switch machine, continued to be remotely controlled from AF. Finally, in mid-1970, work began to transfer AF Tower's controlled trackage to a new centralized traffic control machine located in the Acca Yard Office Building at Richmond. At the same time, AY Tower --a similarly-styled building in Richmond-- was likewise being cut over to the new machine. During December, 1970, AF Tower operators once again only controlled the plant within AF's interlocking limits. By the end of January, 1971, the last operator --probably M. G. ''Mickey'' Rexrode, who worked first trick-- turned out the lights and signal maintainers secured the door. Around 1973, the tower building shown abovwe was razed. A smaller green prefabricated structure had been built about 100 feet to the east of the tower; which housed air compressors, relays, and an emergency local-control model board.

This is a view of the tower's rear, looking northward (according to track direction; actually, the track at this point is running west to east as trains travel northward). The pipes in the foreground were used to condense moisture in the compressed air used to power the switch machines. The compressors are located within the building just inside the wall to the right of the condensing pipes. The doorway at the rear of the tower opened into the battery and relay rooms, with a stairway to the right along the inside of the rear wall to the second story where the interlocking machine and operator's office was located.

Here's a close-up of turnout #37. This is on track four (closest to the camera) which was the nortbound freight track into Potomac Yard that was about a mile further north behind the photographer's back. Not visible in this scene are the two freight tracks into and out of the Southern Railway's Alexandria Yard, which were to the left out of view. AF Tower is also just out of view, at the top left of this picture, but the maintenance of way section house is faintly visible.

This is a typical Union Switch and Signal electro-pneumatic switch machine that was installed in 1921. All electro-pneumatic switch machines were removed in the 2001 interlocking rebuild described below, and replaced with electric switch machines.

AF Tower was originally equipped with a compressed air whistle that was used for communicating with train crews, signal maintainers, or maintenance of way personnel. This was mounted on the southwest corner of the upper story. By the 1960s, it was replaced by a horn mounted between the front upper windows of the southward-facing wall, trackside. One can also see an industrial spur beyond the interlocking, which ran off of the northward freight track into the Southern Railway's Alexandria Yard. During the 1960s, this spur was used for unloading gravel for a cement plant. In 2002, this has been replaced by the Metrorail Alexandria Repair Shop and Yard. The area is now known as the ''Eisenhower Valley'' with office space, retail, and residential areas completely replacing the former industrial space.

This view is looking north trackwise (actual direction is east) at the northward home signals into AF Interlocking on the Southern Railway. There were three tracks at this point: at the left is the North Passenger Track. The middle track, just to the photographer's left, is the South Freight Track. The North Freight Track is to the right, with Alexandria Yard about a half-mile straight ahead. Note the doll signal above for the South Freight Track; this track was not signaled northbound. A northbound Southern or C&O passenger train is apparantly on approach since the operator would not normally line up a route through the interlocking more than a few minutes ahead of the train, usually when it was ''OS'd'' by CR Tower about 3/4 mile south of this point.

These are the air compressors mentioned earlier, located in the south wing of the tower. The circuit board was for the control of these compressors and were the responsibility of the signal maintainers, not the interlocking operator.

This scene of the relay room is directly below the operator's office, with the cabinets placed along the back wall. Behind this wall were the steps leading upstairs to the operator's office. Note the wiring trunks leading from the cabinets to the ceiling; these entered the base of the interlocking machine on the floor above.

This is a close-up scan from the first picture above. A wooden walkway led from the tower building to the track, for the operator to get on or off local passenger trains that were authorized to stop for employees. It was also used for standing trackside to hoop up train orders to the engine and train crew. Further to the right is the section gang house.

The Rebuilding of AF Interlocking in 2001

Following passenger train discontinuances in the 1960s and 1970s, the #2 track between South Franconia and AF was removed from service, leaving double track between these points. During the 1990s, both Potomac Yard and Alexandria Yard were closed so that real estate could be redeveloped. All of these contributed to a rail traffic decline and reduced interlocking activity at AF, reaching its low-point around 1999.

As 2000 approached, the Virginia Railway Express commuter train routes to Manassas and Fredericksburg added runs each year as passenger volume grew. This spurred a rebirth in AF Interlocking's importance, since these two commuter routes merged at this point for the remaining mileage through northern Virginia to Washington, DC. Consequently, plans for renovation and redesign were proposed. Work commenced in early 2001 and was completed during November of that year. In general, both the northward and southward interlocking limits were extended, wider-radius turnouts were installed, and the North Alexandria remote interlocking was removed from service.

Near completion of the work, Vic Stone transcribed and supplemented the contents of relevant Norfolk Southern and CSX Transportation general orders:

Summary -

- Signal suspension on RF&P side starts at 2100 on Friday.

- 2 DTC blocks - "Alexandria" from South RO to AF, "Ravensworth" AF to Ravensworth

- New #4 track, "AF Siding" (signalled) and AF set-off track in- service (see below).

- Speeds changed (see below).

- NS changes start on 9:01 AM on Saturday. New control point "VAL" just south of AF on northbound pass track. Signals changed to reflect this and new signals on Horn Track (details below).

For the CSX - General Bulletin #114, Baltimore Div, RF&P Subdivision, Effective 2059, Oct. 12

- North Alexandria interlocking retired

- original Seminary interlocking retired

- New Seminary interlocking in service, MP 103.9 (at S. Quaker Ln)

- New interlocking and trackage in service at AF: new #4 track in service (right next to #3 track), new AF siding in service MP 104.3-103.9. Both of these tracks are controlled by the CQ dispatcher. New AF set-off track in-service (switches off AF siding).

- "South Freight Track" officially renamed "#1 track", and speeds changed on all tracks as below:

Between CFP 108.6 and CFP 107.4: passenger-65; TOFC-60; freight-55; other-45.

Between CFP 107.4 and CFP 105.2: passenger-70; TOFC-60; freight-55; other-45.

Between CFP 105.2 and CFP 104.8: all trains-40. (unchanged; Alexandria station).

Effective 2100, Oct. 12; General Bulletin #116

- Signal suspension in effect between South RO (CFP 109.0) and Ravensworth (96.7)

- DTC limits:

"Alexandria" block - South RO (CFP 109.0) and AF (CFP 104.3)

"Ravensworth" block - AF (CFP 104.3) and Ravensworth (CFP 96.7)

- Power switches at new AF, Seminary interlockings will be handled by switchtenders under direction of CQ dispatcher. All trains must ascertain that their route is properly secured before operation over these switches.

- Southbound trains at South RO must have both the Alexandria DTC block and a signal at South RO before proceeding (see below).

- Signal indication at South RO and Ravensworth governs route only, not track occupancy ahead.

- Power switch at Slater's Lane off (renamed) #1 track will be spiked for normal movement. Trains operating on #1 track are not required to obtain permission from the CQ dispatcher to proceed through this interlocking.

- Maximum speed during signal suspension - 59 for passenger, 49 for freight

- Any train that receives a cab signal indication must be aware that the cab signal alarm is still active.

NS - Operations Bulletin #O-84, Effective Oct. 13 (Sat), 9:01 AM.

Signals removed from service:

- Northbound automatic signal 102 on the northbound pass track at MP 10.2

- Northbound automatic signal 104 on the northbound freight track at MP 10.3

- Southbound automatic signal 103 on the southbound freight track at MP 10.2

- Southbound automatic signal 95 on the southbound freight track at MP 9.5

- Southbound automatic signal 99 on the Horn track at MP 9.9

New signals in service:

- Control point "VAL" (probably named for a signal maintainer), controlled by North End dispatcher Greenville, located on the northbound pass track at MP 9.10 in service as signal 1-R capable of displaying 301-B, 302-B, 307-B, 310-B.

- Northbound automatic signal on northbound pass track at CR Tower will be retained and turned into an absolute signal capable of displaying the follow aspects: 301-B, 302-B, 306-B, 307-B, 310-B.

- Northbound control signal on Main #1 track at CR Tower changed to display the following aspects: 304-A, 308-A, 309-A, 310-A.

- Northbound control signal on Main #2 track at CR Tower changed to display the following aspects: 302-A, 303-A, 304-A, 306-A, 307-A, 309-A, 310-A.

- Southbound control signal governing movements on northbound freight track changed to display the following aspects: 310-B, 302-B, 307-B, 310-B.

- Southbound control signal governing movements on Horn Track at CR Tower changed to display the following aspects: 301-B, 302-B, 307-B, 310-B.

- Southbound control signal governing movements on southbound freight track at CR Tower changed to display the following aspects: 304-A, 304-B, 308-A, 309-A, 310-A.

- Southbound control signal governing movements on northbound pass track at CR Tower changed to display following aspects: 301-B, 302-B, 304-C, 307-B, 308-B, 310-B.

Key to above NS "3xx-x" aspects", G=green, Y=yellow, R=red: (i.e. 301-A = G-R-R; Indication - Clear) which means a three headed-signal, top is green (G), bottom two are red (-R-R). Indication = clear, proceed at authorized speed). The "A" or "B" suffix is usually to indicate a three or two-headed signal with the same indication. This is not a complete list; just a guide for the above. (FG = "flashing green"; FY = "flashing yellow")

301-A = G-R-R, 301-B = G-R; Indication - Clear

302-A = Y-G-R, 302-B = Y-G; Indication - Approach Diverging (= approach limited, Y-FG-R, on CSX).

303-A = Y-Y-R, 303-B = Y-Y; Indication - Advance Approach.

304-A = R-G-R, 304-B = R-G; Indication - Diverging Clear (= limited clear, R-FG-R on CSX).

306-A = FY-R-R, 306-B = FY-R; Indication - Approach Restricted.

307-A = Y-R-R, 307-B = Y-R; Indication - Approach.

308-A = R-Y-R, 308-B = R-Y; Indication - Diverging Approach (= limited approach, R-FY-R on CSX).

309-A = R-R-Y; Indication - Restricting

310-A = R-R-R; 310-B = R-R; Indication - Stop.

The cut-over of old signals to new ones at Af Interlocking was completed in the pre-dawn hours of Saturday, October 20, 2001. Old signal bridges and most other remnants of the 1921 AF improvements disappeared between then and February 2002.

Information derived from contemporary accounts posted in the VRFE group and credited to individual members when known. This web page is copyrighted in 2002; not to be reproduced or incorporated into other information sources without permission. Please Click Here to reach the operator at af_tower

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