MBTA has a bad plan for electrification

Agency needs to take advantage, not discard, electric trolleys

THE MBTA says that it is committed to an emission-free future bus system, but its plans suggest otherwise. Recently, the T published a document justifying its decision to abandon its existing electrification network and replace it with battery-electric buses (with diesel heaters). This decision is supported by the assertions that lifecycle costs for these battery buses would be $40 million less than maintaining the existing electrification network, and that these new buses will be more reliable and therefore use less diesel than the current fleet, which sometimes requires replacement with diesel-powered buses.

These assertions do not hold up under scrutiny because the T relies on a fundamental misunderstanding of bus electrification technology, and uses figures for infrastructure costs which are inflated several times higher than what the T has actually spent for overhead electrification.

A TransitMatters analysis finds that if the existing electrification system were used to power additional routes—as is possible with available, off-the shelf buses—retaining the existing electrification would not only save the T millions of dollars per year, but accelerate bus electrification efforts. Since the T’s current electrification program focuses on replacing electric buses in some of the wealthiest, least-diverse and least-polluted areas the agency serves, the money saved could then be targeted to electrifying buses in lower-income neighborhoods that lack overhead electrification networks. The MBTA’s plan to replace clean buses with battery buses in North Cambridge will result in a net increase in regional emissions, and is a lost opportunity to replace a diesel bus in a community like Mattapan or Chelsea with an electric one.

The first flaw in the T’s document is that it compares the current fleet of electric trolleybuses to battery-electric buse). It assumes that new electric trolley buses would be similar to the existing fleet, and would be unable to operate during any disruption to the overhead wire network. This is a false equivalence. Since the T last purchased electric trolley buses in 2004, every trolleybus on the market comes with a relatively small battery pack and up to 22 miles of off-wire range. These modern vehicles are known as “in-motion charging” buses and can operate during power issues, or when overhead wire has to be removed over some sections for construction, mitigating these concerns the T raises. This all but eliminates the need to swap diesel buses for electric buses and the diesel emissions—and costs—related to replacement service.

Further, we can assume that the energy costs of battery elecrtric buses and in motion c charging buses would be similar in magnitude. The T’s chart shows that electric trolley buses cost somewhat less to purchase and maintain when compared to battery buses. (The document says that it would be difficult to source parts for electric trolley buses, with only five agencies in the United States using overhead wire for bus operations. Yet dozens of cities in Europe use in-motion charging technology; there should be no shortage of parts.)

So where is the major cost differential? It comes from costs for constructing and operating the overhead wire system. Let’s look into these costs further.

The T claims a $33 million cost “for the design and construction cost of upgrading the existing [overhead] system and power substation to a state of good repair.” It’s true that the existing system has been neglected. In fact, rather than maintain the system, the agency has recently posted speed restriction signs, requiring buses to go slowly through areas with bad overhead wires, degrading service as buses are required to travel slowly to avoid “de-wiring.” But rebuilding the overhead network would cost nowhere near $33 million.

First, power substations are shared with the rapid transit system, and the marginal cost of providing additional power to buses is negligible. Second, we know how much it costs to replace overhead wire, and it’s not $33 million. In the past decade, the overhead system in Belmont was rebuilt as part of a MassDOT highway project. Based on documents obtained through a public records request, TransitMatters found that the cost to replace the overhead wire system there cost $1.4 million for 2.2 route-miles. Adjusted for inflation, this is a cost of $750,000 per mile. The rest of the system has approximately 8 miles of overhead wire, and at this rate would cost $6 million to replace. Of that, two miles would be part of a Mount Auburn Street reconstruction project, and would be covered by highway funding at no cost to the T, as was the case in Belmont.

Few support poles in Belmont were replaced in 2015 as the existing poles were found to be sound. If all of the poles were replaced, at the 2015 inflation-adjusted rates, pole replacement would cost about $1 million per mile, which could add an additional $10 million to the cost, although, again, the Mount Auburn Street section would be paid for by highway funding. So the cost to the agency to completely replace the overhead system and support poles would therefore be on the order of $13 million.

The T then shows a cost of $30 million for infrastructure maintenance for the overhead system over the course of 14 years: enough to entirely replace the system every four years. A new system should be relatively inexpensive to maintain. It seems unlikely that the maintenance cost for a brand new overhead system would be four times the cost of the initial replacement.

Adjusted for inflation, Seattle spends approximately $5 million per year to maintain its 70-mile overhead network, a rate of about $72,000 per mile. At that rate, maintenance costs for a 10-mile network would cost about $10 million over 14 years, not $30 million. As the saying goes, if you don’t want to do something, inflate the costs.

Even assuming that the T’s inflated cost estimates prove correct, which is highly unlikely, trolley buses still turn out to be slightly less expensive than battery buses. Yet this does not take into account expanding the number of in-motion charging buses to utilize the existing system more intensely. Today, the overhead wire only powers buses in service between Waverley and Watertown Squares and the Harvard terminal. An expanded fleet of in-motion charging buses could use these and other portions of the overhead wire to charge batteries and then run emission-free buses elsewhere in Belmont, Cambridge, Somerville, Arlington, and Medford, and potentially beyond.

The 77 bus, for example, is a diesel bus which runs beneath the overhead wire from Harvard to North Cambridge. By charging on this wire, an in-motion charging bus could then run to Arlington Heights emissions-free, without any additional infrastructure.

Dayton, Ohio uses in-motion charging technology to extend its #1 bus from the end of its overhead wire network to Wright State University, a distance of 4.5 miles: a mile longer than the distance from North Cambridge to Arlington Heights. The 72, 74, 75, 78 and 96 routes, and potentially some buses on the 57 bus to Kenmore, could do the same.

($ millions) MBTA document TransitMatters calculations
Existing fleet Expanded fleet
Category: 35 BEB 35 ETB 35 IMC 70 BEB 70 IMC
Operations $1.5 $2.6 $1.5 $3 $3
Infrastructure Maintenance $0.26 $30 $10 $0.52 $10
Infrastructure Capital $20 $33 $13 $40 $13
Vehicle Maintenance $17 $18 $18 $34 $36
Vehicle Capital $48 $42 $42 $96 $84
Total $87 $126 $85 $174 $146

In the above chart, normal text indicates MBTA calculations, italic text indicates calculations using data obtained by TransitMatters, and bold italic text indicates calculations using TransitMatters data and an expanded zero-emissions in-motion charging fleet.

This would double the number of buses using the overhead wire network, so the capital and maintenance costs would be spread across more vehicles. If we add up the costs for this larger network—even without assuming any economies of scale from a larger fleet of Iin-motion charging uses—it would be less expensive, by $28 million ($2 million per year), to use in-motion charging buses than battery electric buses. \Without diesel heaters, the in-motion charging buses would truly be emission-free.

Inexplicably, the MBTA has been looking for reasons to remove the overhead bus electrification system for years. Its current rationale, however, doesn’t pass muster. A fiscally prudent and environmentally sound decision would be for T to make a modest investment in in-motion charging technology, and use it to improve service and increase the number of zero-emission buses on the road. If the agency’s first step in electrification is to use faulty numbers to replace existing electrified buses with new battery buses which require diesel for heat, it is a large and expensive step in the wrong direction.

The T has more than 1,000 fully-diesel buses it could be electrifying, many of which operate in some of our least-advantaged, most-polluted communities. The agency’s current plan is so badly misdirected that it defies logic: it invests in wealthy neighborhoods, increases emissions, and has no specific game plan for electric buses where they matter most. We call on the MBTA, the secretary of transportation, and the new MBTA Board to reverse this promptly, before a bad plan becomes an irreversible step backward for equity and the environment.

Jarred Johnson is executive director of TransitMatters.

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Jarred Johnson

CEO and development director, TransitMatters