Quote:
Originally Posted by jmecklenborg
The structure that supports heavy rail obviously needs to be more robust than one that supports light rail, but I don't know why HRT subway is more expensive than LRT subway, other than the use of a somewhat wider bore.
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Quote:
Originally Posted by hughfb3
Longer trains means bigger underground station boxes and more money
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Depends on the city, the Chicago L, New York's IRT lines and the Paris Metro are considered HRT, but their loading gauge is virtually the same as most American LRT systems, from the height to the width to the car length. The only difference is in overall train length, obviously the trains on those HRT systems are longer and therefore the stations are also longer. The sheer volume of passengers who could exit an HRT train also requires wider platforms and more/wider vertical egress.
Even weight is not necessarily a huge difference, LA's "light rail" P2000 cars weigh 98,000lbs per articulated pair while Chicago's "heavy rail" 5000-series cars weigh 114,000lbs, a difference that can be mostly attributed to the slightly longer cars used in Chicago.
When you factor in the safety margins used in engineering, it's pretty safe to say that LA's elevated structures on the
light rail system could easily support the weight of most
heavy rail subway trains, although trains used for mainline railroad service in the US are far heavier due to the FRA's strict crashworthiness requirements that mandate the use of many tons more steel.
TL;DR there is a whole continuum from light rail to heavy rail, and no clear dividing line about how to classify systems.