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Re: The High Price of Precision Scheduled Railroading
Author: Dr Zarkoff
Date: 10-18-2023 - 02:06
> a cheap CTC signal system that did not show siding occupancy upon entering.
Not having track circuits in sidings was an economy move by the purchasing RR.
The WP chose to use a standard CTC system with unbonded sidings, so entering a siding was authorized by a restricting indication (red over lunar), and this indication was displayed regardless of whether the siding was occupied or not.
On the SP, most sidings within CTC were bonded, so if the siding was unoccupied, you entered on a red over yellow (which doesn't require restricted speed). If it was occupied, you would get red over red (stop) signal, and the DS had authorize you verbally to pass the signal for entering the siding (at restricted speed).
> WhenBART first was running M-F only and closing at 8PM, they had corrosion based issuesbetween wheels and rails. Mondays when the tracks went live again, another recalibration.
Before starting revenue service, BART was running test trains, and they got everything working fine. Then they turned on the fluorescent lights in the stations, only to find that these created so much inductive interference in the "track circuits" that it rendered the system virtually unusable.
The corrosion problem arose because overnight moisture would condense on the railhead creating a monomolecular layer of iron oxide. You couldn't see it, but if you wiped your hand over the railhead, you would find a film of rusty moisture on your hand. This layer would act as a half-wave rectifier between the wheel treads and the rails, causing track occupancy detection failures.
> IINM, they installed scrapers on the wheels.
And the SOARS block system. The scrapers are long gone, but I don't know about SOARS.
> Bonus weirdness: SLACK the Stanford linear accelerator found that after Fri evening shutdown of the third rail energy, they had to recalibrate even though they were miles from any BART tracks.
"SLAC". In its Beale St tower, PG&E had a real-time electrolysis map of the Bay Area. The rails in BART's Hayward Shops are insulated from the rest of the system, and the mere act of shoving a car into or pulling one out of these shop tracks using BART's equivalent of a Trackmobile would show up as a momentary blip on this map.
Not having track circuits in sidings was an economy move by the purchasing RR.
The WP chose to use a standard CTC system with unbonded sidings, so entering a siding was authorized by a restricting indication (red over lunar), and this indication was displayed regardless of whether the siding was occupied or not.
On the SP, most sidings within CTC were bonded, so if the siding was unoccupied, you entered on a red over yellow (which doesn't require restricted speed). If it was occupied, you would get red over red (stop) signal, and the DS had authorize you verbally to pass the signal for entering the siding (at restricted speed).
> WhenBART first was running M-F only and closing at 8PM, they had corrosion based issuesbetween wheels and rails. Mondays when the tracks went live again, another recalibration.
Before starting revenue service, BART was running test trains, and they got everything working fine. Then they turned on the fluorescent lights in the stations, only to find that these created so much inductive interference in the "track circuits" that it rendered the system virtually unusable.
The corrosion problem arose because overnight moisture would condense on the railhead creating a monomolecular layer of iron oxide. You couldn't see it, but if you wiped your hand over the railhead, you would find a film of rusty moisture on your hand. This layer would act as a half-wave rectifier between the wheel treads and the rails, causing track occupancy detection failures.
> IINM, they installed scrapers on the wheels.
And the SOARS block system. The scrapers are long gone, but I don't know about SOARS.
> Bonus weirdness: SLACK the Stanford linear accelerator found that after Fri evening shutdown of the third rail energy, they had to recalibrate even though they were miles from any BART tracks.
"SLAC". In its Beale St tower, PG&E had a real-time electrolysis map of the Bay Area. The rails in BART's Hayward Shops are insulated from the rest of the system, and the mere act of shoving a car into or pulling one out of these shop tracks using BART's equivalent of a Trackmobile would show up as a momentary blip on this map.
