by Jersey_Mike
aem7 wrote:The new mileposts signs you see are in whole mile and half mile increments and are part of the PTC wayside installation program. Train Dispatchers will be using whole mileposts as well as the half mile markers to input speed restrictions or work zones into the PTC computers. Start date is 12/31/15.Not sure why the ACSES installation would need new wayside milepost signs unless it is to provide visual indication of the enforcement point, but then isn't that what the <S> signs are for? Amtrak, which has been using the same system for over a decade now on parts of the NEC, did not need to install new mileposts.
Limited-Clear wrote:You are incorrect about it slowing things down, it will actually speed things up, speed restrictions must use places that are identifiable, such as bridges with milepost location, stations or whole mile markers, now the half mile posts are going in restrictions will be more precise and you won't have such big restriction areas
I can't speak for what SEPTA does, but NORAC allows for speed restrictions to be marked down to any specific milepost location. If whatever ACSES system/procedure SETPA is using requires half mile granularity that would indeed be worse, especially where one has the TSR signs out at the actual site of the restriction. Perhaps this is only for "unflagged" speed restrictions.
aem7 wrote:Temporary speed restrictions (TSRs) will be sent to the train using the half mile posts at each end of the restriction. Road crossing that are out of service will use the road crossing's specific mile marker and will bring the train to a mandatory stop some 50 feet prior to the crossing. In layman's terms, it's a combination of GPS locations, digital radio signals and transponders located in the gauge of the rail.ACSES should not need to use GPS. Location tracking is performed using the balises and wheel rotation.
Limited-Clear wrote:PTC enforces speed limits, it also stops engineers from getting too close to stop signals, the system unless butchered won't slow things down, now CSS on the other hand does slow things down with cab signals dropping to more restrictive signals further away, remember PTC is an overlay to CSS, running normally and PTC will pretty much stay quiet, Amtrak trains that are running in PTC territory aren't seeing massive slow downs, they still run ontimePTC does slow things down because of the "error bars" in the on board speed curve calculating. If you read the Amtrak rulebook the system that SEPTA is planning to use will bring a train to a positive stop up to 1000 feet away from the signal itself and the only way to allow the train to close up is to use the stop release that then requires restricted speed through the interlocking even if the signal upgrades. This is problematic for making station stops (think Trenton) as trains will likely be unable to platform properly and the rulebook specifically instructs the dispatcher to provide a more favorable signal indication for stopping trains if at all possible to avoid constant use of the stop release procedure. Delays from restrictions may be less noticeable, but the engineer will have to slow some distance sooner than they used to be able to (ie by the speed sign itself).
Also remember that there is already a safety factor of about 20 to 50% built into all speed restrictions. PTC layers an additional safety factor onto the safety factor. A speed restriction may say 30mph, but the true derailment speed may be 50 or 60mph. Instead of using PTC as a backup to prevent a train from hitting the overturn speed it will simply further enforce the already conservative restriction for a greater length of track.
