05-16-2019, 08:57 AM
(05-15-2019, 01:53 PM)Section ThirtyOne Wrote: Are there rules/regulations for this sort of things? ie. Signals/barriers must be activated when a train is within xxx metres of a crossing?
For a crossing in the middle of nowhere there's three detection zones, an 'island' under the crossing itself and one to either side extending out some distance. When multiple crossings are close together, detection zones are shared between two or more. For each zone the system sends an AC signal down one rail, with the axles of an approaching train shorting it to the other for detection. The inductance of the rails affects the signal in a measurable way, which changes as the train gets closer. This lets the system calculate both distance and speed, activating the gates based on predicted arrival time. The Transport Canada Grade Crossings Handbook says (more or less, it's complicated) that gates have to activate at least 20 seconds before the train arrives. It's an analog world however so each track section behaves differently and the math can't be hard-coded, there was a lot of tuning done with stopwatches while police protected the crossings in the system's early days.
While there's no argument that some of the crossings need better tuning, I worry that they won't be allowed to re-tune without police guarding the crossings again, lest an adjustment cause the gates to drop late. Hopefully this can happen yet before they start simulated service, or its going to be a lot more painful as headways decrease. I doubt they'll ever hit perfect, but I hope they can at least get them all to under 25 seconds. University was amazing when I was there around lunch yesterday, that's how they all should be.
Another thing I've noticed are the 'no left / no right / train' signs are way too conservative, particularly the ones out of the Graybar driveways on Hayward. For northbound trains they don't clear until the train has made it quite some distance down Courtland, leaving a driver blocked for 30 seconds or more after the train has passed. I haven't sat around to watch but I'd be surprised if their employees haven't already developed bad habits, and I fear "the boy who cried wolf" effect is going to cause an accident there one day.
...K