Why the Broad Street Line is so slow between Walnut-Locust and Lombard-South

Route 10 Trolley rides along the 40th block of Lancaster Avenue. Trolleys operate at 35 mph inside the tunnels and abide by PennDot regulations above ground.

About two years ago, Jonah Eaton, director of legal services at the Nationalities Service Center, noticed the southbound Broad Street Line train would slow down between some stops.

He says it’s particularly noticeable heading to South Philly between Walnut-Locust and Lombard-South.

He asked Curious Philly, The Inquirer’s forum for questions about the city and region, why the train slows down along that section of the line and whether a change had taken place recently.

Travelers wait for the train at the South City Hall station. All four tracks from Race-Vine to Lombard-South are 20 miles per hour because of the curve heading into City Hall.

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Maximum authorized speeds on BSL, MFL and trolleys

The train speeds are 50 mph on the local tracks and 70 mph on the express tracks on the Broad Street Line, said Sean Sharpe, chief instructor for transit at SEPTA.

The speeds vary based on the infrastructure of the tracks, he says. The maximum authorized speed on the Market-Frankford Line is 55 mph. For the trolleys, the speed inside the tunnels is 35 mph, and once above ground, they are regulated by the speeds PennDot sets on the roads.

On the Broad Street Line, speeds aren’t consistently 50 mph or 70 mph throughout the whole line because of the way the tracks were built. Trains typically slow down in areas where there are curves in the tunnels to avoid derailments, he said.

“The speed is designed to withstand the way the system was built,” Sharpe said.

Eaton was right, trains do slow down around City Hall, Sharpe said.

All four tracks from the Race-Vine stop to the Lombard-South stop require trains to drive at 20 mph because of the curve heading into City Hall, he said.

“It’s all about the curvature of the track in that area, so we have to slow the train down just to get through that [area],” he said.

As soon as a southbound train leaves Walnut-Locust on Track 1, the speed drops to 10 mph as it heads into the Lombard-South station. The local northbound track in that area isn’t as curved, so the train can travel at 25 mph.

The slow speed isn’t a recent change, Sharpe said. “It’s always been 10 mph leaving Walnut-Locust.”

SEPTA has systems in place to ensure that the trains operate at the appropriate speeds.

The Market-Frankford Line has automatic train control, which alerts the train operator if the train is going too fast, and the train can itself automatically stop if it isn’t slowed down in a timely manner. The Broad Street Line has a more manual system that depends on the train operator taking action to slow down the train.

“Sometimes people say ‘why is the train always going slow in this area?’” Sharpe said. “It’s all safety related. It’s not a thing where the operators are taking their time, or just trying to make people late — it’s just the way the system is designed to slow down in certain areas so that they won’t have any mishaps.”

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