Kicking the tires on battery-electric buses
The better option now for Greater Boston is the electric trolley bus
THERE IS GROWING CONSENSUS that our transportation system needs to move away from fossil fuels toward a cleaner electric-powered future. This is not only an environmental issue. It goes directly to the quality of service and the cost and reliability of the equipment. Whether we are talking about the intercity rail system or the inner core bus network, the move toward electric power is as necessary as it is inevitable.
A recent article in Commonwealth rightly took the MBTA to task for failing to commit to an investment plan that would migrate the current diesel and diesel-hybrid bus fleet to a cleaner electric fleet. The authors promoted battery electric buses as the “readily available solution,” a characterization that deserves some fact-based tire-kicking. If there is general agreement among advocates that the T should be moving toward a cleaner and more cost-efficient bus fleet, we need to be sure that we are proposing the right solutions. In our view, the right solution is not (at this time) to move toward large scale adoption of battery buses, but to re-invest in and expand the MBTA’s fleet of electric trolley buses – a technology with a 100-plus year proven record of performance.
As we transition away from the grip of fossil fuels, we must understand the options available to us and assess their current utility. When it comes to bus transit, there are multiple options, but they are not all on equal footing with regard to their readiness for widespread adoption, at least in the New England climate. Battery electric buses are rapidly improving and have begun to be deployed in measurable numbers so that we have some real-world results that we will discuss further. But for now, and at least for the foreseeable future, especially in any city with serious winters, the electric trolley buses are far superior to the battery buses, which simply do not have the available power to adequately heat the bus when the temperature is below freezing.
“The trolley bus?” you ask with raised eyebrows. The very name evokes images of another time, the sentimental glory days of transit that exists in the minds of those for whom the past is forever enshrined as a better time – Judy Garland, resplendent in technicolor, singing “Clang, clang, clang went the trolley.” Was there ever such a time?
Today, electric trolley buses are clean, reliable, and relatively inexpensive to maintain. They are, in short, exactly what we should be investing in and for multiple reasons. They have a longer useful life than diesel, or any current expectation of battery electric (we hope and expect this will change over time as batteries improve) and have lower maintenance costs than diesel and thus much lower lifecycle costs. So, a trolley bus system is significantly cheaper to run even factoring in the maintenance of overhead wires. Electric trolley buses currently have advantages in terms of capacity, proven lifecycle performance, daily performance for high volume, high frequency routes, and performance in extreme weather and on hilly terrain. Thankfully, we already have the facilities to run and maintain electric trolley buses; we just need to renew and expand this commitment in the strategic places where it makes the most sense.
Articulated electric trolley buses are superior to diesel in snowy conditions because the rear two axles (out of 3) are powered. This would also be true for future battery electric buses. Today, we take articulated diesel buses out of service in snow because they fishtail, a result of only the rearmost axle being powered. But that’s where the electric trolley/battery bus equivalency ends, with the clear advantage going to the trolley.
First, there is no good track record for battery electric buses in extreme cold; in fact the opposite is true. Second, because electric trolley buses don’t have to carry an engine or big heavy batteries on board, they offer additional seating capacity which makes a big difference on high demand routes. Finally, a double decker problem: battery buses need additional time to recharge (fast charging technology remains at a suboptimal stage) and tend to get many fewer real world miles than advertised, meaning the buses can’t complete as many runs in a day. As a result, transit agencies have found that they must purchase additional battery electric buses to run the same service than then they would need with either diesel, hybrid, or electric trolley buses. Purchasing battery electric buses at this time is simply not a fiscally or operationally prudent idea. Some real-world examples underscore this point.
Recent experience with battery electric buses in Moscow offers a cautionary tale. Like many people who buy into tech pizzazz, Moscow’s mayor believes that trolley buses are outdated. He has busied himself with replacing the city’s extensive electric trolley bus network with battery electric buses. Unfortunately, the result has been nothing short of a disaster. The batteries don’t last long enough for a full day’s work, so buses have to swap in and out of service. To run the same frequency that used to be provided with 46 trolley buses, Moscow had to procure 82 battery electric buses. This was last September, even before the notorious Russian winter, which is when batteries can be sure to drain most rapidly.
In China, the much-discussed expansion of battery electric buses slowed down dramatically for the same reason. Shenzhen trumpeted itself as the city of the future when it became the first city in the world to convert its entire bus fleet to battery electric buses, all bought from local manufacturer BYD. Subsequently, the installation rate stalled, and China’s battery bus fleet is now growing at much lower rates than in past years as the government has decided against continued subsidization of this technology.
Notably, Shenzhen has never in modern history recorded a temperature below freezing; the average temperature there in January is 59 degrees. Also notably, the government’s actions following the Shenzhen bus fleet experiment make clear that the results have been disappointing: the installation rate in other cities has slowed and the government has opted away from further large-scale conversions. In any event, what works for Shenzhen will simply not work for cities with harsh winters, like those of Northern and Central China – or Boston.
In America, battery electric bus introduction has not done well in wintry conditions. In the suburbs of Minneapolis, a trial run of a battery bus saw the battery barely last a single round trip on a particularly cold weather day. In Duluth, the battery electric bus trial requires separate oil-fired heaters for the bus.
Diesel buses do not have this problem, because the internal combustion engine is so inefficient it produces enough otherwise unused waste heat anyway. Diesels have more range than batteries because the energy density of the fuel is so much higher than that of batteries.
Thankfully, electric trolley buses do not have this problem. They require more energy in winter, just as battery buses do, but they get their power from overhead wires rather than dragging their own power plant, which allows them far superior performance in all conditions – just as trains powered by overhead wires or a third rail have far superior performance to diesel trains. Swiss cities, where winter temperatures are about as cold as in Greater Boston (and where the buses are run punctually and without interruptions), are not only maintaining their extensive electric trolley bus networks but are even strategically expanding them.
There is an important innovation that combines the flexibility of running without trolley wire and the reliability of the trolleybus called in-motion charging. Trolley buses today have small batteries designed to allow the bus to go off-wire for a fraction of a mile to detour around obstacles. In-motion charging expands this concept by equipping the bus with enough battery for about five miles of off-wire travel. This technology is increasingly popular in small Central European cities because it allows all the advantages of trolley wire while allowing the avoidance of the most difficult (and expensive) points of installation and maintenance (i.e., intersections, rotaries, and low underpasses).
In-motion charging is an especially good fit for Greater Boston because of the region’s unique street network. Here, buses run on shared trunk routes with many other buses, and then branch out. For example, many different buses share Washington Street and Warren Street in the South End and Roxbury, and then branch to outlying destinations in Hyde Park, Mattapan, and Dorchester. A few miles of trolley wire could electrify all of these routes at once, helping improve air quality in those neighborhoods. The Seaport and an expansion of electric trolley bus routes out of Harvard Square are other good places to re-invest and expand the network.
The Federal Transit Administration treats trolley bus wire as fixed infrastructure and will fund it on the same basis as rail transit. Fortunately, the costs of wiring a few miles of street are not high, and in-motion charging ensures that a short project would have wide-ranging benefits to transit users as well as to people in our close-in communities who currently have to breathe the diesel fumes of many buses every day.Here’s the bottom line: the MBTA can have an expanded, renewed electric fleet today and be on the front lines of breaking in the new battery electric bus technology with readiness and commitment for large-scale adoption when the technology is ready. The T should continue to explore and introduce battery buses via small-scale pilots. Meanwhile, a renewal of our electric trolley bus fleet can serve us well for generations. The new buses should come equipped with in-motion charging, increasingly a standard feature on new trolley buses; asking any of the usual manufacturers to include it should not pose a problem. At the end of the day, long after today’s battery electric buses are retired, trolley buses will still be in service.
Alon Levy is a freelance writer and member of TransitMatters, working from Berlin. Josh Fairchild is the co-founder and president of TransitMatters; he works as a commercial real estate and finance attorney in Boston. James Aloisi is a former state secretary of transportation, a principal in TriMount Consulting, and a member of the TransitMatters board.