Railroad Forums 

  • Unidirectional vs Bidirectional

  • General discussion of passenger rail systems not otherwise covered in the specific forums in this category, including high speed rail.
General discussion of passenger rail systems not otherwise covered in the specific forums in this category, including high speed rail.

Moderators: mtuandrew, gprimr1

 #869399  by mtuandrew
 
Myrtone wrote:
ExCon90 wrote:Some years ago, Milan introduced off-center unidirectional cars with more overhang on the right side than on the left because of limited clearance between tracks in the street. To achieve a wider body they had to put all the increased width on the right side of the vehicle (presumably they counterweighted the cars to compensate for imbalance). No way to do that with bidirectional cars.
And this wouldn't be necessary on North American or Australian systems because of wider track centres. Even Prague has never had trams like this as far as I can tell.
I wouldn't say that - the Twin Cities of Minnesota had a few narrower-than-average streets on which double-track lines were required, and that system used wider-than-average cars until its 1954 abandonment. As such, they were forced to offset the car bodies about half a foot for clearance.

Were such a line to be reconstructed now, either the equipment would be narrower, on-street parking would be eliminated, or the line would be single-tracked or made gauntlet at those points. It'd only be a problem in existing systems, and would once again remove the need for unidirectional equipment.
 #869434  by Myrtone
 
mtuandrew wrote:I wouldn't say that - the Twin Cities of Minnesota had a few narrower-than-average streets on which double-track lines were required, and that system used wider-than-average cars until its 1954 abandonment. As such, they were forced to offset the car bodies about half a foot for clearance.
But did that system have a narrower than average track centre width, at least in those streets?
mtuandrew wrote:Were such a line to be reconstructed now, either the equipment would be narrower, on-street parking would be eliminated, or the line would be single-tracked or made gauntlet at those points. It'd only be a problem in existing systems, and would once again remove the need for unidirectional equipment.
Remove the need for unidirectional vehicles? Quite the opposite that is, balloon loops (which turn around trams quicker) remove the need for cabs at both ends, and when combined with all kerbside stops, doors are only needed on that side. So there will be more seats and most fixed front facing. If the equipment is narrower, than the extra seating gained in this way will be even more of an advantage.
 #879854  by walt
 
Disney Guy wrote:The Philadelphia Kawasakis in terms of interurban versus city versions differed in interior layout only. The body shells are the same except for the door arrangement.

From a description of the cars from back in 1981 I believe a Red Arrow Kawasaki will run with no problem on the city lines, with a trolley pole substituted for the pantograph. And a city Kawasaki would negotiate the track with no problems on the Red Arrow lines with a pan substituted for the pole.
The suburban ( Red Arrow) versions of the K-Cars are longer than the city versions. This difference goes back to the pre- SEPTA equipment, partcularly the 1949 St Louis Cars whose Double Ended PCC bodies were of what was known as the "Chicago" Length. ( This refers to the length of the longer than standard PCC cars built for the Chicago Surface Lines). Because of this, although the city versions of the K-Cars could easily run over Red Arrow trackage, and could probably so without changing their poles for Pans, the Red Arrow versions would have problems negotiating the turns inside Philadelphia, including the turns inside the subway tunnel.
 #884047  by modorney
 
> Here in Australia, according to that aforementioned Australian poster on skyscraper city, many public transport users also do not like facing each other

I find this fascinating. Here (San Francisco Bay Area) we have a commuter rail system called ACE, and much of the seating is what may be called "club seating" - four facing seats. A few also have a table (ACE uses Bombardier Lozenge cars). On ACE, most people have no problem with facing others. In fact, it's quite a congenial crowd.

However, on BART - a hybrid commuter rail/subway - many people do not want to sit backwards, which I can somewhat understand. Personally, I have no preference, I'd much rather sit (forward, rearward, laterally or even on a box) than stand, and would take whatever I get.

The whole seating paradigm is quite interesting.
 #886054  by walt
 
modorney wrote:>

The whole seating paradigm is quite interesting.
Seating on rail vehicles has been an issue for passengers for decades. The most "popular" type, I suspect, has always been forward facing cross seating. Those transit operators who had lines with high passenger traffic preferred longitudinal seating, which provided the greatest amount of room for standees, ( and didn't require "walking over" seatbacks in double ended bi directional equipment when the cars reversed direction) but this arrangement ( at least in Philly) was the least appreciated. Because of this, cars were placed into service with a combination of cross seating and longitudinal seating in several variations. The old "walkover" cross seating which was applied to double ended equipment provided ther most flexibility, as passengers who wished to sit facing each other could "walkover" one seatback so that two seats faced each other. When these passengers left the vehicle, the seat backs could easily be walked over and returned to the "standard" arrangement. ( Some railroad and interurban cars also had seats which swivelled, accomplishing the same thing as the walkover seats). It seems that since walkover or swivel seating is somewhat costly, car builders now use fixed seating, and simply face some seats in each car in each of the "standard" directions-- ie there will be some forward facing seats, some rear facing seats and some longitudinal seating in the same car.
 #886388  by Disney Guy
 
While walkover seats could be arranged so that groups of people could face each other, I think that was not intended.

Many models of walkover seats have the lower part move (slide slightly) in a fashion that decreases the knee room between a pair of seats for persons facing each other.
 #888556  by justalurker66
 
Disney Guy wrote:While walkover seats could be arranged so that groups of people could face each other, I think that was not intended.

Many models of walkover seats have the lower part move (slide slightly) in a fashion that decreases the knee room between a pair of seats for persons facing each other.
It doesn't even need to do that. If the spacing between seat bottom edges is enough for one set of overhanging legs then having walkover seats move just the seatback would leave space for one set of overhanging legs despite there being two seats worth of people sharing that gap. But, as you noted, if the seat slid slightly as well it would provide those two seats worth of passengers even less room.

NICTD (South Shore Line outside of Chicago) put walkovers on their latest cars. It is a good idea ... especially with the longer (up to 58 mile) trips involved.
 #895695  by Myrtone
 
modorney wrote:I find this fascinating. Here (San Francisco Bay Area) we have a commuter rail system called ACE, and much of the seating is what may be called "club seating" - four facing seats. A few also have a table (ACE uses Bombardier Lozenge cars). On ACE, most people have no problem with facing others. In fact, it's quite a congenial crowd.
In street transit resistance to travelling backwards can be much stronger because unfamiliar passengers are on the lookout for the next stop.
 #952618  by Myrtone
 
Another way of turning around a unidirectional tram is with a turntable, this is done in San Francisco with Cable Cars, there were two in England in Christchurch and Huddersfield, one in Guadalajara, Mexico, and one near Soligen, Germany which was in regular use until 2009.
The only example I know of for electric trams was one in Kiev in the 1960s.

Image
 #952741  by electricron
 
McKinney Avenue Trolley in Dallas is building a new turntable at Cityplace so it can use unidirectional trolleys as well. Presently they're only using bidirectional trolleys.
 #1285425  by Myrtone
 
Here is a video of that turntable.
By the way, the KCR light rail is one of the few new build systems with unidirectional rolling stock with doors on only the left. They too run them in coupled pairs. All but one juction on the network are trianuglar. See this map, though it may be dated. It is especially unusal in combining unidirectional running with high level platforms.
 #1285454  by dowlingm
 
In Toronto we're about to (well, in six years) have both paradigms: 600V unidirectional, trolley pole* nonstandard gauge downtown, 750V full pantograph bidirectional uptown. Steve Munro points out that fewer doors and one cab = more seats, especially on the high floor cars where you couldn't stand on the steps either. The loop system is a bit of a pain though given the grief wheel squeal can cause for neighbours of loops, plus reversing out of a disruption ahead is off the table.

* being converted to panto capable but it doesn't look like main CLRV fleet will get pantos prior to retirement in 2024.
 #1285647  by Myrtone
 
Yes, but the TC lines have a wider minimum curve radius and a lesser ruling gradient than the legacy system. Many big European unidirectional networks (most using pantographs, some with 750v) don't have as many problems as Toronto, they have plenty of intermediate turnbacks, or use triangular junctions for shortworking. They either have small bidirectional fleets, or couple unidirectional trams back-to-back when a line is templorarily truncated.
If the loop system is such a pain, why are you still buying unidirectional rolling stock rather than switching to bidirectional running?
 #1285668  by talltim
 
Patrick Boylan wrote:You must exercise your imagination more. One could do it with bidirectional cars if the clearance problem was on only 1 side, and the cars never looped or wyed, or had skyhook rotate them.
But if the issue was clearance between tracks then it wouldn't work with bidirectional trams, trams on one track would have the body shifted away from the other track and the ones on the other track would have the body shifted toward the first track and you would end up with exactly the same (lack of) clearance as you started with
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