Man - have I been racking my 60 year old memory over that one! He probably did, but I don't remember my grandfather ever expounding on it. But there have been some fairly plausible guesses on that thread already, though.

I do remember wooden "trunking" in a few places, but usually near interlockings (such as at the tower bridge in Sacramento) and at Mikon on the woodland branch; but it was off to the wayside a few feet from the tie ends. Never saw anyone working on it though. Trunking was nothing more than a very long box, usually set at ground level and attached every so often to a post driven into the ground. It was used to protect wiring or air piping which was strung along the ground instead of on a pole line.

This trunking looks too small to be carrying propulsion current around an island circuit - but who knows for sure anymore. It is plausible. It certainly could be carrying track circuit wires or other grade crossing signal circuits across main street - in lieu of jacking a pipe under the road. The SN was just chuck full of unusual methods - usually less expensive - for doing many different things. Things such as mounting signals on wooden posts, flashing lunar grade crossing approach lights on a traction pole, center fed track circuits, etc.

Those center fed track circuits, used for overlapped ABS, were fed from a pole mounted transformer, stepping down from 2200 vac commercial power (carried on the top cross arms) to track voltage. This would be in the center of a several mile long block, and would feed down the rails in both directions to the track relay at the home signal at each end of the block.

Pole line wires were then fed through contacts of the first track relay of the next block, the track relay at the far end of the home block, and finally through the near end track relay to a line relay at the home signal. When the line relay at the home signal was energized, the block and its far overlap were clear, thus the signal was lighted green. A distant signal at least braking distance away from the home signal simply repeated the home signal - green for green and yellow for red. The approach signals, labeled "D", most places did not go red as the train passed.

Talk about simplicity! There were places where it got more complicated than this, but commonly, it was just that simple. Now the introduction of a grade crossing signal, with its short east, west, and island track circuits, just jazzed up the complication level whole big bunch! Anything to cut the complication on the SN - even if unusual. It is possible that what looks like trunking shown in the photograph was used to bypass these center fed block signal track circuits around those grade crossing track circuits, though I don't know why they wouldn't have gone to the pole line for that - this was probably a very unusual case, such as the presence of a nearby home signal.

One other possibility, In the late fifties and early sixties, the SN was experimenting in the Concord area with "Audio Frequency" grade crossing track circuits, some with loops and tuned shunts, in various configurations. I do not recall if Main Street was one of the them. But being a retrofit, and a "temporary" test configuration at that, this trunking could have been used - on the cheap, or maybe the loop itself was in the street. Certainly, audio feed wires running down the track to a remote connection site, might need to be located in the center between the rails to prevent cross coupling of audio currents.

On a side note, SN's ABS system was originally built by the electrical contractor Wismer and Becker. It was Mr Wismer that got my grandfather his job at the SN in 1929. He knew my grandfather from the Kennecott Copper mines, where they had previously worked together. The Wismer & Becker Co. was still around in 1970 and built several very large interlockings at BART. Later, they were absorbed, but went on to build signal systems for San Diego and Sacramento trolley systems, and worked as a sub on the BART Pittsburg extension. How's that for nearly a hundred years of service to the railroad industry. Though spun off by the sharks that absorbed them (we all know what that does to a company), they are still around (with a different name).

OPB

PS. --- It looks from the long shadows in the picture, that this was the last run of the day returning. If it was, I was on it! rode the cab (very crowded) down Ohmer hill as we flew down the hill to the new Olivera Rd crossing. Excited as a sixteen year old could get, I asked how fast we were going - I was bluntly told not to ask. By the time we got to where the old school trains let off the kids for Mt Diablo High, we stopped for a few minutes, as one of the cars had sticking brakes - or so I was told. Because of the overcrowding in the cab, I took the opportunity to go back to a seat in a harriman car for the rest of the ride through Concord and the orchards (what was left of them) to Walnut Creek.

Memories!

OPB