document: Members of the Aslef union have backed three days of action next week in a dispute over driver-only operated trains.
  But Govia Thameslink Railway (GTR), which has claimed all Southern services could be halted, have argued the strike would breach customers' rights.
  A separate Southern network strike by RMT members has entered its second day.
  Southern has said the hearing, which started earlier, will continue into Thursday with a judgement expected at 14:00 GMT.
  Aslef members have also launched an indefinite ban on overtime which, coupled with the RMT action over changes to the role of conductors, led to about half of Southern's services being cancelled on Tuesday.
  The long-running RMT dispute, which has seen several strikes throughout 2016, is set to continue in the run-up to Christmas.
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  Maria Caulfield, the Conservative MP for Lewes, has warned of the impact a strike by Aslef drivers would have in Sussex.
  She said: "Southern has said if the Aslef strike goes ahead next Tuesday, they won't provide any trains whatsoever."
  She said Gatwick Express and Thameslink services would be unaffected, but in areas only served by Southern there would be no trains.
  The latest strike began on Tuesday and is due to finish at 23:59 GMT on Thursday.
  A spokesman for Southern said the company had "led the way" in trying to resolve the dispute but claimed the RMT would not move on the "fundamental issue" of helping Southern "modernise" its train service.
  Gary Hassell, from the RMT, said: "We are definitely prepared to talk, as far as I'm aware Southern haven't spoken to us for months.
  "But we won't be stopping the strike because we've got a mandate from our members."
  00:01 Tuesday 6 December to 23:59 Thursday 8 December (RMT)
  00:01: Tuesday 13 December to 23:59 Wednesday 14 December (Aslef)
  00:01 Friday 16 December to 23:59: Friday 16 December (Aslef)
  00:01 Monday 19 December to 23:59 Tuesday 20 December (RMT)
  00:01 Saturday 31 December to 23:59 Monday 2 January (RMT)
  00:01 Monday 9 January to 23:59: Saturday 14 January (Aslef)
summary: The parent company of Southern rail has gone to the High Court in an attempt to stop a drivers' strike.