[This post has been updated]

Many commuters complained of long waits and crowded trains during the Tuesday evening commute on Metro.

About 3:30 p.m. Metro said its crews reported a “weather-related heat kink” in the rail between Takoma and Silver Spring on the outbound train track, according to a press release released Tuesday night.

Metro officials explained that heat kinks are caused when ”the metal rail expands due to extreme heat and direct sunlight.” As it expands, Metro said, the rail “loses its proper alignment, making it necessary to take the track out of service until repairs are made.”

Red Line trains shared a track between Silver Spring and Takoma.That created train congestion, crowding and delays in both directions.

Metro said , “Some trains were turned back at strategic locations to preserve adequate service levels elsewhere on the line.”

Crews used heavy machinery to reset the rail to its proper alignment. The work continued overnight.

Metro also apologized “for the inconvenience many of you experienced and thank you for your patience.”

— Dana Hedgpeth

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Original post: Tuesday’s hot temperatures are slowing the commutes for rail riders on some Metro and MARC trains.

Spokesman Dan Stessel warned via Metro’s main Twitter account that Red Line trains were single-tracking between Silver Spring and Takoma.Metro was experiencing “heat kinks,” a problem caused by rails expanding. Stessel said delays were running 15 to 20 minutes, but the repairs may take several hours.

Meanwhile, the Maryland Transit Administration warned of delays on its Camden and Brunswick lines due to heat restrictions issued by CSX, the railroad that owns the tracks for those routes and operates the trains for the MTA.

According to the MTA, heat restrictions are issued for the two lines when temperatures are forecast to reach near 90 degrees or in the event that temperatures experience a 25-degree change. Track components can expand, contract or shift under those conditions. Trains travel at slower speeds iunder those conditions, operating under delays of 5 to 15 minutes.

CSX also sends inspectors out to check the tracks during those conditions, which can cause delays as trains headed in opposite directions use one track through those areas. The restrictions don’t apply to the Penn Line, which has a higher temperature threshold for heat orders.

Amtrak operates MARC's Penn Line, which connects Washington and northeastern Maryland through Baltimore. The MTA said some Penn Line trains were being delayed due to congestion, including problems caused by a disabled Amtrak train.

CSX operates the Camden Line, which runs between Washington and Baltimore, and the Brunswick Line, which provides service between Washington and points north and west, including Frederick and Martinsburg, W.Va.

As of 5:15 p.m. Virginia Rail Express was reporting that all of its trains were operating on time.