Light Rail versus "Streetcars"

Catenary on pantograph has the advantage also of being strung so as to constantly sweep accross the collector as the car is operated. Notice the overhead the next time that you're riding underneath a set. It will constantly move left or right and return. This gives a wider area of friction on the collector's surface, reducing the wear. A trolley shoe in a harp rubs along it's wire in only one spot, and as a result, a trough is made very quickly in the running area of the shoe. Superior current collection, ease of cross-overs and turnouts, more heavy-duty, etc. leave the pantograph superior to the wheel or shoe in my opinion.

Correct with Catenary and Pantographs vs wheel or sliding shoe.

The point that the catenary wanders across the pantograph is also correct. This prevents grooves on the pantograph and maximizes the area that the pantograph uses, minimizing wear and tear.

Light rail is exactly that. The weight per yard of light rail is considerably less than rail from a freight RR. By comparison, a streetcar weighs considerably less than a loaded freight car or engine etc. That also explains why a streetcar, trolley etc. can easily go on RR tracks with no problems and will not load down the tracks or ROW.

I don't know about California but, in the east, one of the things made necessary by the arrival of 'light rail' vehicles was heavy rail.
Back when I was a kid 85 lb./yd. was the highest standard for urban railways, even for rapid transit. Nowadays, 100 lb./yd. is the bare minimum. Incidentally most light rail/streetcar lines still have wheel treads and flanges to the old AERA standard which is much
narrower and the flange less deep than the MCB flange on the railroad. Operation of an ordinary LRV or trolley on RR track
must be done very carefully and is not practical for regular service. This is worldwide, more extreme in the UK. Their cars can not even run on American streetcar track.

I don't know about California but, in the east, one of the things made necessary by the arrival of 'light rail' vehicles was heavy rail.
Back when I was a kid 85 lb./yd. was the highest standard for urban railways, even for rapid transit. Nowadays, 100 lb./yd. is the bare minimum. Incidentally most light rail/streetcar lines still have wheel treads and flanges to the old AERA standard which is much
narrower and the flange less deep than the MCB flange on the railroad.

Modern LRT lines use 115# rail, since it is the lightest weight railroad rail commonly rolled in the U.S., so it is cheaper. The original San Deigo line designer chose 100#, but it turned out to be more expensive per foot than the 115#.

Regarding flange profiles, most LRT's use a standard railroad flange, but sometimes with a slightly narrower wheel tread so the wheel fits into the truck frame. So most can use standard (therefore cheaper) railroad special work.

I know that either Calgary or Edmonton, but not both, uses the smaller streetcar flange, but I forget which. This means cars cannot move between the two cities without changing wheels!

Pittsburgh, which stuck to their wide track gauge, went to a wide wheel tread on the LRV's but kept the shallow flange so that they would run with the PCC cars, which (since they had narrow streetcar treads) needed to use flange-bearing frogs.

The term light rail might have been a marketing technique to make people think it wasn't the old fashioned streetcar. Let's give San Diego some credit then. I was born in 1959. They were the first of the new light rail installations in my lifetime, and they proudly advertised their initial line as "The Tijajuana Trolley", or "The San Diego Trolley".

LRVs also have a higher designed running speed and in comparable situations, a lower schedule speed (see Commonwealth Avenue, Boston where it amounts to 8-12 minutes difference).

Except for the Newark City Subway where LRT's replaced PCC's and schedule times went up. Though this being NJT, they raise all their schedule times every year it seems.

Irish Chieftain wrote:High-platform LRVs also do street-running. Note the C-Train in Calgary, Canada. Low-platform LRVs also run mostly on reserved alignments (such as New Jersey's light-rail routes).

There's another example for high-platform LRVs, that do street-running: The Metrolink in Manchester, UK. In this case, the LRVs run both on reserved alignments and on the street, especially in downtown Manchester.

gardendance wrote:The term light rail might have been a marketing technique to make people think it wasn't the old fashioned streetcar. Let's give San Diego some credit then. I was born in 1959. They were the first of the new light rail installations in my lifetime, and they proudly advertised their initial line as "The Tijajuana Trolley", or "The San Diego Trolley".

You may be right to claim that the term "light rail" is a marketing technique in some cases. I think the term is used very differently. Take the Docklands Light Railway (also DLR) in London, UK. It is entirely different from a streetcar. It's automatic, runs on an elevated alignment and uses a current rail like a subway. http://www.tfl.gov.uk/corporate/modesof ... /1530.aspx

neroden wrote:Pantographs seem to be used consistently for higher-speed operations, but I've never quite figured out why pantographs are necessary at high speed. I'd think the rolling friction of a trolleypole would be better.

In addition to the factors mentioned in other posts, there is another rather simple explanation for this---- trolley poles have a tendancy to be dewired ( pulled) from time to time,--- pans don't. ( PCC Cars on Philadelphia's subway surface route 13 frequently "pulled" their poles on the curve, eastbound, where Chester Ave runs into Woodland Ave in Southwest Philly. As the car would take the curve, you'd hear a "thunk" and the car would lose power, because the pole had dewired. The trolley retriever would lower the pole to the roof of the car to avoid damaging the overhead- hence the "thunk". This, of course, required the operator to exit the car and re-wire the pole) Additionally, in the 1930's, the High Speed Cincinnati & Lake Erie RR "Red Devil" interurban cars used to have to slow down some on curves to keep from pulling their poles at the 80 plus MPH speeds at which these cars were run.