Late trains lead to overcrowding, missed connections, and of course a longer than necessary trip. A single train delayed can directly affect a thousand people in peak hour, and often causes knock-on delays that affect thousands more. There are many causes, including poor maintenance leading to track, signal and train faults, and single-track bottlenecks.
This picture shows an evening delay in the counter-peak direction, but the late arrival of trains into the city leads to delays for peak-direction services as well.
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