Re: High heat level restrictions going up all over the place
Date: 06-21-2021 - 08:51
Makes sense, with air temp exceeding 100-110F all over the western US. Leaves one wondering how HSR will do in the Valley. Fresno and Bakersfield last week were both over 110.
Rail expansion joints exist, but seem to be actively ignored in the US, though they are used in Europe. That might have to change as the climate warms and extremes become the norm. A broken rail on a conventional line can cause a wreck, but if everything stays aligned it might not, especially on a secondary, lightly-loaded, low-speed line. More importantly, it can be fixed fairly quickly. Sun kinks, now, could be another story, especially on a high-speed line on a structure.
Another temperature-related issue that isn't seen much in the US, because electrification is mainly for urban transit lines, is wire droop in hot weather. Constant-tension arrangements for the wires are needed to adjust for temp changes, more so than for the rail. Sac light rail has that for portions of the system where catenary is used. But it doesn't have enough adjustment range - at 110+ the wires droop and often get pulled down by a train causing service disruptions. That's an annoyance and a couple hours work to fix the wires where trains operate at 50 mph or less. It could be more serious if a 150 mph train snags the wire.