The cables used by ‘cable cars’ are fraying, prompting car ban on Powell

A cable running under Powell Street shows wear and tear from traffic conditions. Courtesy of SFMTA

A cable running under Powell Street shows wear and tear from traffic conditions. Courtesy of SFMTA

More than 55,000 feet of taut steel cables run underneath San Francisco.

That constant stream of woven metal puts the word “cable” in cable cars. Now, those cables are fraying more often than ever before.

The San Francisco Municipal Transportation Agency is moving fast to fix the problem. Its solution is to ban private autos on Powell Street, where the cable cars run.

“We’re doing this because of safety,” said Ed Cobean, senior operations manager of SFMTA’s cable car division.

The plan is called the Powell Street Safety & Improvement Pilot. If passed by the SFMTA Board of Directors on Nov. 3, by Thanksgiving private autos would be banned on Powell between Ellis and Geary for a year and a half.

The linkage between traffic and frayed cables is complex.

At issue is Powell Street downtown congestion. Cable cars were designed in the 1800s, when the only traffic was the occasional horse-drawn carriage. In San Francisco now, a new swell-tide of private autos constantly cause cable cars to stop in the streets.

When cable cars stop, the cable still runs through the car’s dies, the metal clasps which grip the underground cable for movement. The dies need to maintain constant contact, even in neutral. The cables run through the metal dies, which chafe against one another, a normal function of cable car life.

But the increased stop-and-go nature of traffic on Powell Street means the cable cars are stopping more frequently than usual, causing the cables to fray far more frequently. The longer they sit, the more that friction increases.

“In the holidays it’s so congested we can’t move,” Cobean said. “The cable gets damaged.”

The damage is not a “snap,” he said, but either a fray or a “weld.” The cable and the plates can fuse together, Cobean said.

Instead of being replaced once every 50 days, as in the year 2000, the cables are now replaced every 30 days on average, according to SFMTA.

A cable running under Powell Street shows wear and tear from traffic conditions. Courtesy of SFMTA
A cable running under Powell Street shows wear and tear from traffic conditions. Courtesy of SFMTA

“These conditions make a severe cable car accident more likely,” SFMTA wrote in a factsheet for the Powell Street project.

But limiting cars would not only benefit cable cars, but also bolster pedestrian safety in the area by limiting vehicle turns along Powell Street. More than 4,000 people per hour walk on Powell Street during its peak period, according to the SFMTA.

Often when SFMTA considers limiting car access or parking to a street, local businesses protest. But Karin Flood, executive director of the Union Square Business Improvement District, told the San Francisco Examiner businesses are mostly in favor of Powell Street going partly carless.

The reason is simple: experience.

When the Central Subway forced closure of Stockton Street last holiday shopping season, BID and SFMTA made a special promenade with AstroTurf and holiday decorations, business boomed by nearly 30 percent, Flood said.

Merchants hope a carless Powell Street would create a European-style promenade. “If pedestrians make up a majority of the district, you have to make the experience positive,” Flood said.

Merchants are still concerned tourists may lose access to hotels, and that stores would face problems having goods delivered.

SFMTA is aware of those concerns, and will evaluate ways to mitigate them during the pilot. SFMTA will also create eight new commercial loading zones.

Market Street went carless only a few months ago, with only taxis, buses, bikes, commercial and emergency vehicles allowed between 3rd and 8th streets on Market.

Robert Lyles, an SFMTA spokesman, said this is not a sign of a trend of carless streets.

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