The £1.5 billion deal will also see new fleet rolled out across the network.
Hemsby: Murdered Student May Have Been Raped
Police believe a student from Hemsby may have been raped before being killed on the Thai island of Koh Tao.
The bodies of Hannah Witheridge, 23, and her boyfriend, David Miller, 24, were discovered on a beach on the tiny island on September 15.
A bloodstained garden hoe, believed to be the murder weapon, was found nearby.
Police investigators said they believe three people were involved in the attacks.
Speaking to the Bangkok Post, Lieutenant General Panya Mamen, commissioner of Provincial Police Region 8, said: "Two of the suspects raped and killed Witheridge while another one witnessed the murder.
"We're confident we have a very high chance of finding the suspects.''
Officers have collected 200 DNA samples from people on Koh Tao and the results are expected at some point this week.
Two different semen samples collected from Ms Witheridge's body are the basis for the DNA analysis, the force told the newspaper.
A group of Thai footballers are the latest people to be questioned by police amid fears that the hunt for the killers has stalled.
A spokesman for the Royal Thai Police confirmed that DNA samples were taken from "more than eight'' footballers - who reportedly threw a late-night party at the nightclub where the victims spent their final hours - and officers were awaiting the results.
Last week police colonel Kissana Phathanacharoen said a reward of 700,000 baht - roughly £13,300 - was now being offered for information which leads to the arrests of the culprits.
Post-mortem examinations revealed that Ms Witheridge died from head wounds, while Mr Miller, from Jersey, was killed by severe blows to the head and drowning.
Around 150 police officers were posted to Koh Tao as part of the murder investigation but detectives are apparently no closer to finding the killer.
Mr Miller's father, Ian, earlier said that he believes his son stepped in to help Ms Witheridge during an altercation.
He told the Daily Mail: "It has become clearer and clearer that it is quite likely David was stepping in to help a girl who was in trouble.''
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