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Michael Druker

Yep. Sure, I understand the motivation -- to "connect" all those places. But not only does it take a relatively long time to get to a station that's close but in the wrong direction, it's also plain humiliating to be in such a situation. (Note: My opinion is not based on experience of any such systems.)

Alon Levy

Two-way loops are often invaluable parts of a city's transit network, even when they're not really two linear lines connected at the ends. Examples include Tokyo, London, and Moscow, whose circular lines provide crucial transfers.

PointSpecial

What about Chicago's Loop? It has spurs radiating out from it (thus the Loop is the destination in many respects, with different nodes), but it is circular and it is one-directional.

Cap'n Transit

No, the Chicago Loop is not one-directional.

Matthew

PointSpecial-

As a Chicagoan, I understand the desire to defend the Loop, but you've glossed over some important points.

First of all, the Loop is not one-directional: the Pink and Orange lines run clockwise, but the Brown line runs counter. Plus, the Green line sort of runs around the northeast side, trying to avoid slowing the other three lines down too much.

Secondly, the Loop is an historical artifact. The L system was originally many independently owned and operated lines which all converged on the central business district. Once the lines reached downtown, the trains had to be turned around some way, so a circuit track was built which allowed the trains to do a loop. The Loop was never intended as a one-way loop as Jarrett describes, i.e. it was never a route in and of itself. Rather, it was a pragmatic solution to a problem caused originally by a bunch of streetcar routes converging on a dense area with no room for turntables.

Besides, Jarrett's point still holds: do you know anyone in their right mind who would take the Brown line from LaSalle and Van Buren to Clark and Lake, and then back? Of course not, only a tourist would do a circuit of the Loop like that. Most people would just walk the 8 blocks.

Dave in KY

While I agree that loops stink, lines also stink. Lines can be okay if their endpoints generate a lot of trips - say an industrial park or airport - but most lines I'm familiar with push out to the hinterland. When it comes time to turn around, who wants to go back to where they just were? Nobody, otherwise they would have gotten off. So you see buses with 55 seats and 0-1 passengers for a mile or five. That's a disaster, it brings down the efficiency of the whole line.

I think loops need to be looked at more closely. If the loop cuts across densitites in an eliptical orbit, it will also have lower ridership in the hinterland, but probably not zero. If the loop runs across constant density, then ridership might be about constant.

Of course all your points about not wanting to run 330 degrees around the loop to go back one stop are coming into play here.

Concentric rings operating in opposite directions?

Jarrett at HumanTransit.org

Dave.

When you talk about "lines" I think you're talking about unanchored lines -- i.e. lines that end in a low-density area. Better network design (and better land use) leads to lines that always end at a major destination, so that there is strong demand all the way to the end.

What you're describing in the latter half of your comment is a two-way loop. As Alon Levy mentions, there are lots of great examples of those, and they work well because they can be treated as two-way lines at any point.

EngineerScotty

Tri-Met has many bus lines that go nowhere are are used by nobody, but seem to be necessary to maintain the taxing district. And many lines that go into the weeds may be ninety-percent empty most of the time, but still provide a valuable service to somebody...

Ari

Re: Melbourne's City Loop:

The City Loop in Melbourne is not a one-way loop, but much more of a distributor loop like Chicago's L. About a dozen suburban rail lines (most with 15-30 minute off-peak headways, however) converge on the downtown, and loop through five stations in the central business district (much like the Chicago Loop). The reason the City Loop shuts down at midday is that, ostensibly, certain stations have more patronage and the goal is to minimise the trip length for those stations (although I'm really not sure; it seems to me that the switch is confusing and not necessary). In any case, at any time of the day, trains run in multiple directions.

That said, the City Loop is not meant for looped travel, as not services make a full loop. Trains enter the loop, drop off and pick up passengers, and then leave. Cross-CBD travel is facilitated by one of several tram lines, although these services are generally a lot slower since they operate at street-level. In fact, there are several parts of the day where it is impossible to get from Melbourne Central to Flinders Street by train, although there are trams that make the trip every minute or two. Since Melbourne's ticketing system covers trams, trains and buses, the fact that the City Loop does not allow for circular travel is not a huge deal.

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