Around 2 hours. Most races are designed in such a way that they last for around 2 hours or approximately 300 kms. Some tracks are longer and some are shorter. In such cases the number of laps is adjusted to ensure that the race distance is around 300 kilometres and the race does not take more than 2 hours to complete. There have been cases where races have been stopped because they exceeded the 2 hours mark and were still running due to rain/accident etc.
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