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Originally Posted by SFBruin
Out of curiosity, why did they decide to use battery-powered buses, rather than trolley-buses, given that the corridor is fixed?
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There are a couple "big picture" reasons for this. The first big picture reason is that overhead electrical contact systems or OCS in transport nomenclature are wildly expensive. There are a multitude of examples, especially in the US, where electrification would be ideal for a number of reasons, whether environmental, aesthetic or just plain "keeping up with the Jones's, but isn't implemented because of the enormous upfront costs. Expenses associated with long term maintenance is also a factor but much less so since electrification usually will represent long term savings in fuel and equipment costs. Also, it's not just stringing wires, expensive and complicated electrical substations are also a requirement even with trolleybuses, but a more minor element with shorter tram lines and trolleybus routes when compared to longer distance light rail, metro or commuter lines. These "plant" costs are so high that in the instance here, if you were going to install OCS, from the operators perspective, you may as well go ahead and just build the light rail now. OCS for trolleybus is different than OCS for a pantograph on a train so expensive future modifications would also be part of the equation.
But...
The other "big picture", and I hate to say this for myself and any other transit buff, is that new trolleybuses no longer have much appeal and future ground-up trolleybus lines are highly unlikely, and that is true globally. A couple reasons for this include that aforementioned high cost of overhead power and the reasoning that if rail is an alternative, the light rail will win out nearly every time for a number of obvious reasons I won't get into here. But the biggest reason is the advances in technology. Battery technology for buses has advanced to a point were a charge is stored onboard and
constant contact with the overhead line is no longer needed. This is especially true of electric buses, but the premise is also true of tram/light rail - time will tell whether that mode is as affected as much. So we are no longer talking about a time where in order to have an electric bus, you needed an electric line. Instead you may have the ability for a bus to complete its entire route on a single charge OR at the very least only required one or two quick boosts with a quick charge station located at a designated stop. This reality represents a huge cost savings for transit agencies, and regardless of whether is puts a tear in the eye of foamers to not see falling sparks at night from a trolleybus wire, it no doubt puts a smile on the face of a transit operator for not having to spend as much money on installation and maintenance of an overhead electric system. All transit buses are going to be electric in the near future, so it's really nothing to fret and if anything you can view it as basically all bus lines being trolleybuses without the wires. This would have been unimaginable before battery technology got to this point.
I do want to stress one point though that will soften the blow for those that think batteries will replace older trolleybus systems. I actually don't think thats the case. Due to the face that legacy systems infrastructure is already in place, and constant overhead power will remain the most reliable, I foresee the trolleybus routes we have now in cities like Philadelphia and even more so in cities like Seattle and San Francisco, where high torque requirements due to the topography, to remain as the overhead is ideal. In my opinion this is likely true of most trolleybus systems worldwide. Especially in cities in Eastern Europe and Asia where that investment in trolleybus infrastructure was made decades ago, they will also remain not just out of inertia but because "if it ain't broke don't..." - you know the rest. In many cases here and oversees these power systems were actually originally for trolleys but were substituted for additional flexibility on congested streets, and especially true in the US, "progress". The wisdom of that is obviously another story entirely. You may see some sections of overhead taken down in areas where the historic nature of the area makes the removal politically popular, and future trolleybus may have a small battery that will get them through the skip. This is actually already true of some trolleybus as well as trams. To come full circle, while I do not believe a new ground up trolleybus line will be built here for all the reasons mentioned, and I think it highly unlikely a ground up route will be built anywhere else, I do see new trolleybus overhead installed in instances of route extensions or where re-routing of existing trolleybus routes is desired. I think this occurance is much more likely to be seen in Russia and Asia than the notion that a Philly trolleybus is ever going to be extended. They can't even bring back former trolley routes with rails in the street and overhead power still hanging - still hanging with diesel buses running under them by the way. They can't even bother converting for trolleybus op's, but let's not start talking about Philadelphia.
So, don't be sad. The trolleybus is probably a thing from the past, but will continue to exist due to the fact the infrastructure is already in place, but is unlikely to be built upon due to the advancement of battery technology which is close to delivering the conversion of all polluting diesel buses to clean electric operation. That can only be a good thing. I hope this helped answer your question. Apologies for the long-winded-ness.