Quote:
Originally Posted by caligrad
In my opinion, and I may get a lot of slack for this, I really never considered the entire Vermont corridor necessarily needing heavy rail. Vermont gets really wide south of gage, so wide to the point that metro could slap LRT down the median and call it a day... Maybe even wide enough beginning at Slauson. But that tricky little section between the 10 and Slauson I foresee getting killed politically just on the basis that the Vermont corridor is far from being one of the denser corridors in the county that could actually use the heavy construction for HRT. I know we all wish that our rails were either grad separated or buried but truth be told, density to warrant the construction costs falls off quickly once you're south of the 10. In the minds of politicians, They can care less if the stop lights/traffic cause our trips to be an extra 15-20 mins a trip, especially if it means doing it the LRT way means they save billions but at the same time get the job done.
|
LRT subways have just as much capacity as HRT subways.
HRT is better for fully grade-separated corridors because using third rail allows for smaller tunnel diameters (cheaper subway construction) and less obtrusive elevated secions (no poles and wires hanging overhead.)
There's no question that any rail transit on Vermont should be built either at-grade or elevated south of Gage. The question is, should it be fully elevated, or should it be partially at-grade. That would be based on the capacity question; would a surface alignment have enough capacity. Surface alignments have lower capacity because of things like impact to traffic (if given full signal pre-emption), maximum allowed speed (typically, when in a median, no faster than the speed limit for cars), average running speed (which can be slow enough to impact capacity if signal priority, rather than pre-emption, is used), road block length (limits how long trains can be), etc. Some of these factors can be mitigated by adding grade separations to a surface alignment.
You can build heavy rail at grade too, but usually that's only done in existing railroad corridors due to the need for full grade separation because of the third rail.
If a fully elevated alignment is required due to the above constraints, then Heavy Rail would actually probably be cheaper and also more desirable. If any portion of the line is to be at-grade, then Light Rail is the better choice.
Prev
Linear Mode
