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Re: Speed restrictions on the UP (old SP)
Author: SP5103
Date: 05-16-2013 - 21:19
Signal systems require a train to be able to stop at a red signal. Due to stopping distances, this typically requires an advance warning by a yellow approach signal. To increase advance warning, the advance approach (often a flashing yellow) was added, normally giving two signal blocks of advance warning to a red signal. Grades, operating speeds and changing tonnage/braking effort all conspire against an engineer to stop their train safely.
There are plenty of places where the signals are so close together that multiple hard yellows will precede a stop signal. It may not have been the signal engineer's miscalculation, but changing braking/train handling situations that suggest a lower maximum speed is needed.
One BN main I worked had a tonnage restriction that reduced maximum speed from 49 mph to 45 mph for loaded unit trains - in dark territory. Did that 4 mph make a difference in stopping distance or safety?
Not to worry - PTC and digital braking will solve all these issues ...
There are plenty of places where the signals are so close together that multiple hard yellows will precede a stop signal. It may not have been the signal engineer's miscalculation, but changing braking/train handling situations that suggest a lower maximum speed is needed.
One BN main I worked had a tonnage restriction that reduced maximum speed from 49 mph to 45 mph for loaded unit trains - in dark territory. Did that 4 mph make a difference in stopping distance or safety?
Not to worry - PTC and digital braking will solve all these issues ...
