<Tr> <Th_colspan="2"> Technical </Th> </Tr> <Tr> <Th> Line length </Th> <Td> 50.45 km (31.35 mi) </Td> </Tr> <Tr> <Th> No. of tracks </Th> <Td> 2 single track tunnels 1 service tunnel </Td> </Tr> <Tr> <Th> Track gauge </Th> <Td> 1,435 mm (4 ft 8 ⁄ in) (standard gauge) </Td> </Tr>

How many tracks does the channel tunnel have
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