FRIENDS OF THE BROOKLYN QUEENS CONNECTOR, VIA THE NEW YORK TIMES

Renderings from New York City’s proposed Brooklyn-Queens streetcar (known as the BQX) omit any hint of the overhead catenary wires that are integral to many electric rail lines, especially those plying busy city streets. The images, along with a survey of recently built and in-progress streetcar projects, raises the question of whether Mayor Bill de Blasio intends to introduce new streetcar technology as part of the project.

A reporter asked about the BQX’s intended power source at de Blasio’s February 16 press conference on the streetcar plan. City transportation commissioner Polly Trottenberg answered that the 16-mile line would not use overhead wires, implying that the BQX would rely on batteries or perhaps another power technology.

Batteries in new streetcars are generally used in a hybrid arrangement, where they power the vehicle for short parts of the line with no overhead wires and are recharged via catenaries on the rest of the route. This is the case for lines recently opened in Seattle and Dallas. The 3.3 mile QLINE under construction in Detroit was recently called the “most ambitious off-wire plan” in the U.S. by consultant Rick Gustafson. Only about 40 percent of the Detroit route will have overhead wires.

Overseas, wireless streetcars have made more progress. One report indicates a fully battery-powered tram is being tested over a run of about six miles in Sapporo, Japan. A five-mile route in Guangzhou, China uses “supercapacitors” that receive electricity at each station stop, rather than continuously along the route, according to a story by National Public Radio.

It isn’t clear, however, if the technology used on these systems would be useful to the much longer BQX. The website of Brookville, a major U.S. streetcar manufacturer, describes supercapacitors as a supplementary rather than primary power source for its cars. In addition, if city officials sought federal funding for the BQX, Buy America requirements would make it virtually impossible to import the technology used in Asia unless a manufacturer in the U.S. could amass the requisite expertise and technological capability.

In-street power would be another alternative to overhead wires. Three tram lines in Bordeaux, France, run on power from a third rail between the tracks whose design makes it safe for pedestrians. It’s possible that extensive replacement or relocation of underground utilities during streetcar construction could make such a system cost-effective, though experts say overhead wires would be significantly less expensive in any event.

With no details or clear plans unveiled, it’s impossible to know whether the de Blasio administration intends to avoid overhead wires for aesthetic reasons, as a cost-saver, or something else. But for a streetcar plan whose usefulness has been extensively questioned, attempting to push the envelope with unproven “off-wire” technology now in use only on relatively short streetcar routes would only seem to add to the project’s known risks.