For our new readers: Despite the fact that systems like the planned London Thames Cable Car are often officially called “Cable Cars,” they are more often than not Gondolas. This can be confusing to cable transit novices. To make it easier: Cable Cars are supported from below (like cars) and Gondolas are supported from the top (like ski lift gondolas). This is an error of nomenclature, nothing more.
For Cable Cars Lesson 1, click here. For Cable Cars Lesson 2, click here. For Cable Cars Lesson 3, click here.
At it’s core, a Dual By-Pass Shuttle is nothing more than a fusion of a Single Loop Shuttle and a Dual Loop Shuttle.
The basic concept here is of a multi-station, two vehicle line where both vehicles run on the same set of guide rails – except at the intermediary station(s), whereby the tracks split in order for the vehicles to by-pass one another at a central platform.
A simplified diagram describing how a Dual By-Pass Shuttle operates. The above image depicts a theoretical line with one intermediary station, but it is theoretically possible to have several intermediary stations. Image by CUP Projects.
The advantage of this set-up is to have a similar capacity level as the Dual Loop Shuttle, but with the lower costs and reduced geographic footprint associated with having a drastic reduction in the amount of elevated guideway required.
This cost advantage does, however, come with one major trade-off: Whereas the Dual Loop Shuttle can offer near 24/7 service as it’s two vehicles move independently, Dual By-Pass vehicles operate in tandem with one another. This means if one vehicle is out of operation, both vehicles are out of operation.
Similarly, in times of maintenance and cleaning, the entire system needs to be shut down.
Currently, the only known Cable Propelled Transit system in the world that uses a Dual By-Pass configuration is the new automated people mover in Venice, Italy:
The intermediary station of the Venice APM. Note the track split. Image by Luca Fascia
Notice how when not in the central intermediary station, vehicles operate on a single length of track. Image by Luca Fascia
10 Comments
Simply a horizontal funicular. The passing loops needs to be exactly in the middle between the terminal stations. If there are more than two stations, they need to be placed symmetrically. Both cars have the same speed at the same time.
Excellent way of putting it. Though it’s important to remember that not all funiculars use a By-Pass. Many use a dual track, or single track completely.
But the cars could be detachable. The station won’t have to be the middle if one car could detach and wait for the other to arrive. This adds some delay going one direction but allows flexiblity, the cars just have to avoid being on the same track at the same time.
Theoretically, yes. Though I’ve never seen such a configuration.
What Seth describes would be a pinched loop system with a very short passing loop.
True, but in essence we’re talking about combining a pinched loop and a by-pass. That’s never been done. I think there could be some very useful applications there.
Kind of a neat concept.
For rail, for example, there has to be a fairly large clearance in terms of time, if two trains going in the opposite direction want to share a track. With this you can have sidings where trains pass each other at full speed – since they are constrained by the cable, they’ll never hit each other unless something goes horribly wrong.
I wonder whether one could built a sort of large cable car, more train like line, with a couple of stations at fixed intervals, all on one track except for sidings, to get a fairly high capacity line across a choke point like a bridge or tunnel, where only one ‘lane’ is available.
There are a lot of ways to get around asymmetrical station layouts. You can increase dwell times at certain stations, modulate speeds throughout the track, etc. In essence, very basic programming changes.
I noticed the emphasis on central in:
“whereby the tracks split in order for the vehicles to by-pass one another at a central platform.”
Does central hear mean midpoint of the line’s extent, or an island platform? I don’t think the system would constrain the design to an island platform, but I wanted to check.
Side platform would be possible. Island platform just offer more advantages for elevated design. Smaller overall station size. And only one set of facilities like stairs,elevators, passenger information, etc.