Electric buses are coming to Pittsburgh. The Port Authority of Allegheny County (PAAC) introduced a handful of battery-electric buses to service in the past year, and has placed orders for additional electric buses to be used on the forthcoming bus rapid transit service between Downtown and Oakland. Around the country, transit agencies are ordering electric buses, and subsidies for electric buses may become significant to federal transportation policy. With all the recent buzz around electric buses, you could be forgiven for thinking electric buses are new technology—but they’ve actually been around for decades. Different to the battery-powered vehicles in the press today, trolleybuses—electric buses which draw power from overhead wires—were once far more prominent, though only survive in a few US cities (Boston, San Francisco, Seattle, Philadelphia, and Dayton). Returning to the trolleybus—aided by some advancements in battery technology—is the best way to electrify the United States’ bus fleet, and Pittsburgh happens to be a great place to start.
Quick aside on trolleybus history: Pittsburgh is actually somewhat unique in never having hosted trolleybuses. Many cities used trolleybuses as a sort of transition between streetcars and diesel buses, but Pittsburgh kept its streetcar network relatively late (into the 1960s) and went straight to diesel buses. However, nearby (but much smaller) western Pennsylvania city Johnstown did have a trolleybus network! (Ok, back to the point).
Enter In-Motion Charging
In Europe, cities and bus manufacturers have been combining trolleybus and battery technology, to produce in-motion charging (IMC), described by transit writer and best practices expert Alon Levy in a really good post on their blog Pedestrian Observations (which was the inspiration for this post). As noted here, in-motion charging works best “when relatively small electrification projects can impact a large swath of bus routes. This, in turn, is most useful when one trunk splits into many branches.” Pittsburgh’s extremely radial, trunk-based bus network could be particularly well-suited to trolleybuses which use IMC: putting up wires on a few major corridors could bring pollution-free bus service to much of the city.
Trolleybuses For Pittsburgh
The most important variable in planning an IMC network is the off-wire range of the vehicles. Longer-range IMC buses on the road right now include Kiepe Electric’s buses in Solingen, Germany, with an off-wire range of 18 km (11 mi). Kiepe is supplying the electrical equipment for Dayton’s new trolleybuses, which have an off-wire range of 24 km (15 mi), according to Dayton’s Regional Transit Authority. For the purposes of this, the hypothetical Pittsburgh IMC bus has an off-wire range of 20 km, which seems optimistic against most IMC systems in operation (which average between 5-15 km off-wire), but is probably do-able given the range of more recent buses.
So where should the city be stringing up trolley wires? Here are the four corridors that I think would be the strongest, and which, together, would bring all-electric bus service to a large swath of the city:
- Fifth Avenue: Wiring Fifth Avenue between Downtown and Craig Street would be sufficient for the four main Fifth Avenue routes to complete their trips and return off-wire. (The 71A & B take two different routes to Highland Park, an approximately 10 km round-trip; the C & D go to Wilkinsburg, just over 14 km). The 71A and 71C could also pick up wires on Centre Avenue (see below) which would further shorten their off-wire segments.
- Forbes Avenue: The Forbes Avenue routes branch further east, in Squirrel Hill, so wires should extend to Murray Avenue (also good because getting up said hill would be a not-insignificant battery drain). The 61D to the Waterfront mall—a 12.4 km round-trip—should be fine, and the 61B might just make it to Braddock and back (18.8 km), but the 61A and (especially) C are >20 km round-trips, so are difficult without opportunity chargers (more on this later) at their outer termini.
- Liberty Avenue & Butler Street: Wiring the Liberty Avenue spine between Downtown and Lawrenceville, around 33rd Street, would provide enough power easily for the 88 (11 km) and maybe for the 86 (19.6 km, though this could have help along Centre Avenue) and 87 (18 km). You’d have to extend wires along Butler up to about 55th Street to bring the 91 just within round-trip range; this is a bit far, but might be worth it because this section is shared with the circumferential 93 and the 87 (which would bring that route within safe all-electric range).
- Centre Avenue: Between Downtown and East Liberty, Centre Avenue hosts several bus routes, and contains some significant gradients in the Hill District, which make it ideal as a trolleybus corridor. Wiring Centre Avenue as far as Negley or Euclid would provide sufficient power for the 82, and shorter sections of power for many more routes: the 54, 71A/C, 81, 83, and 86 all have segments on Centre Avenue and, with wires on other sections of their routes, could be made fully-electric.
With the four corridors above, much of Pittsburgh’s East End would have fully-electric, pollution-free bus service. You may (rightly) point out that this proposed list is very East End-biased—this is really where the trunk/branch structure is strongest. In other areas of the city, the trunks are shorter and the branches longer, less desirable for IMC: this includes Carson Street in the West End and South Side, and North Avenue in the Central Northside.
There are other corridors that would work. Wiring Second Avenue as far as the Pittsburgh Technology Center could make the 57, 58, and (maybe) 56 fully-electric; Murray Avenue hosts frequent service and is hilly so may be worth it. Short but busy sections of route where buses’ boarding times are long, such as Penn Avenue in East Liberty, can also work for IMC.
The busways are the most glaring omission above—the reason they were left out above is because they are a real mixed bag of branch lengths, but enough branches could work with opportunity chargers at termini. If these were available, the busways would, of course, be very attractive routes for electrification—there are already several busway branches, such as the P17, P71, and G31, which are within the 20 km off-wire range. The other omission is the South Hills routes: these share a trunk (the Mount Washington Tunnel), but that is already wired for light rail, and trolleybus and light rail wires are not electrically compatible (trolleybuses need a separate return wire, rail vehicles do this through the running rails and therefore do not).
Opportunity charging refers to the ability of vehicles to recharge briefly while they sit in one place, either at certain bus stops or at a terminal. The required infrastructure is a short section of wire which buses can connect to while standing, as employed in Solingen, Germany, and being considered in Gdynia, Poland. Placing opportunity chargers at terminals effectively doubles the off-wire distance that vehicles can travel, as they would only need enough battery power to make it to the terminal, rather than to the terminal and back to the wires. Opportunity chargers would allow, for example, the 61A & B to run to their terminals in Braddock (11.8 and 9.4km from Squirrel Hill, respectively), and the 61C to its terminal in McKeesport (15.9km). This would also open up several East Busway branches—including the P67 (a 9.7 km branch), P7 (14.7 km), and P68 (19.7 km)—to IMC operation, as well as the remaining West Busway branches, the G3 (16.9 km), and (maybe) the 28X (22.2 km).
Why We Should Want Trolleybuses
Surely—you may be thinking—battery-powered buses could do this just as easily? And if they can’t now, at the rate technology progresses, in a few years’ time they might—so won’t all these wires will have been wasteful? Nope! There are several key, fundamental advantages of trolleybuses over batteries.
IMC buses recharge their batteries while in service. This is a major difference with exclusively battery-powered vehicles, which need to stop and recharge with sufficient power to complete their next trip. This can take place at terminals, but only where terminal layovers are long enough to fully recharge; otherwise, battery buses have to be removed from service for some amount of time in order to recharge. The lack of ability for battery buses to recharge in service also means their batteries—a significant portion of the cost of an electric bus—need to be larger than those of an IMC vehicle. Battery-only vehicles are also less resilient: the range of battery-electric buses has been shown to suffer in cold weather and on steep hills—two things Pittsburgh is infamous for having in large amounts.
Most importantly, trolleybuses are extremely well-proven technology. Cities around the world have operated trolleybuses for over a century, and there are numerous long-standing precedents from which Pittsburgh (or any other city) can draw best practices on trolleybus operation. Philadelphia’s pilot of battery-electric buses has come to a halt, while its 98-year-old trolleybus network soldiers on. Dayton has operated trolleybuses since 1933 and, as mentioned above, has recently invested millions in its continued operation. And these are just the two examples nearest to Pittsburgh—looking internationally can provide further guidance on trolleybus operations, especially with the addition of in-motion and opportunity charging.
Re-Embracing The Trolleybus
If we want to develop or expand trolleybus and IMC networks, we have to encourage them. Right now, the Federal Transit Authority (FTA) subsidizes purchases of battery-electric (as well as fuel cell and hybrid) buses through its Low or No Emission Vehicle Program. But this program doesn’t cover the infrastructure costs of hanging new trolleybus wires. As “fixed guideway” projects, agencies building new trolleybus wires need to apply for FTA Capital Investment Grants instead, placing them in competition with rail transit projects. This should be changed. The Clean Transit For America Act, which increases funding to the Low or No Emission Vehicle Program, should change the guidelines of the program to include trolleybus/IMC vehicles, as well as the cost of wiring. This is an important policy change not only on the off-chance that a city like Pittsburgh decides to develop a new trolleybus network—but because the strategy for bus electrification in existing trolleybus cities should be extending wires, not scrapping them for batteries, as Boston seems worryingly to be considering.
IMC can create a “best of both worlds” electric bus, mitigating the logistical issues with battery-electric buses while keeping their off-wire flexibility—and electrifying a lot of bus service without the cost of wiring every bus route in their entirety. The point of this post was not to say that battery-electric technology is bad; after all, it is advancements in battery tech that allow IMC to work, and which will allow it to improve in the coming years. But electrification of buses is imperative for the climate and for public health. There’s no time to wait for battery technology to advance to the point where it is able to carry an entire city’s bus fleet, at reasonable cost and with acceptable reliability. If we want large-scale bus electrification soon, it is time to re-embrace the trolleybus.