Hot weather conditions across the Bay Area Saturday caused major BART train delays.
BART passengers should expect 10- to 20-minute travel time increases on every trip in the system for the duration of the heat wave currently ravaging the Bay Area, a BART spokesman said.
Train speeds are being reduced in targeted parts of the system as a precautionary measure to give train operators more time to react to any observed abnormal rail conditions, spokesman Taylor Huckaby said.
This is because, though it's unlikely, the extreme temperatures forecast for the next several days could cause the rails to move, Huckaby said.
BART rail is heat-treated before it is installed, which allows for thermal expansion and contraction of the rail in the Bay Area's widely varying temperatures.
However, when temperature variations reach extreme levels, the thermal forces exerted on the rail increase, making rail movement possible, though unlikely, Huckaby said.
The trains that will actually run slower are the ones on outdoor tracks, and the slowdowns will be in effect between noon and 8 p.m. However, "whenever there are that many trains that are slowing down, it can affect all the trains in the system," he said.
BART anticipates these reduced speeds will be in effect at least through Sunday, though the final decision will be based on weather forecasts and track conditions in the system.