Wednesday, June 15, 2011

In the Pipeline

I've had some ideas for blog posts for a while, but haven't been executing for the past couple of days. However, hopefully (maybe) look for these in the coming days:

(1) A post on the hierarchy of parks, from the neighborhood square to the main city greenspace;
(2) A post on Roman-style house construction viz. setback construction;
(3) Finishing my series on the Loop Network (Philadelphia2050);
(4) Concerns with the new zoning code and the comprehensive Philadelphia2035 city plan;
(5) Taking a look at transportation centers in Philadelphia and how they can be improved; and
(6) Whatever else is on my mind.

What will happen? We shall see!


  1. Just one comment, about the loop idea: one-way loops tend to be a really bad idea for terminating services. The Chicago Loop is a flawed compromise, and nowadays cities that want to have one trunk line branching out outside the CBD make the trunk a line rather than a circle. Or if the trunk is a circle, the lines using it use line segments of it, rather than making a full one-way loop (see e.g. the Berlin Ringbahn, or London's Metropolitan and District Lines).

    Good loop service should either be useful for transfer relief, or for multiple linear segments connected to form a ring. The Yamanote Line and similar high-performing loops are really several lines joined together (quite literally in Yamanote's case). It requires a somewhat larger diameter, with a circumference of around 30 km, vs. 5.5 km for your loop. Moscow's Circle Line is also relatively short, at 19 km, but it's useful mainly for simpler transfers between the radial lines, since the radial/radial transfer stations are overcrowded.

  2. As you say, but notice that the system is actually made up of a point-to-point spine which interconnects in such a way as to de facto make a loop, which a secondary layer of service then uses as a mode of quasi-termination. Also, the 8th-Market station has, as a legacy of current operations segregation between SEPTA and PATCO, two platform levels along the "loop" alignment--one through and one stub. This allows an intra-loop termination point.

    So what I'm doing is taking advantage of the interconnections the through-spine (Pennsport-Andorra and Society Hill-Mt. Airy lines) offers to terminate other service, at peak, on the loop. Off peak, there's no reason why the 25th St. Line can't interconnect with the Lindenwold Line, so long as an adequate degree of service can be maintained at all stations.

  3. Fair enough... my complaint is mainly about the Chicago-style one-way looping of some lines, for example the 25th Street El you've just described.