Mr Verster has been facing intense pressure in recent months, mainly due to the rail service's failure to meet targets on punctuality and reliability.
ScotRail Alliance was formed as a partnership involving Abellio ScotRail and Network Rail, intended to improve performance through cooperation between the rail operator and the rail infrastructure company.
Mr Verster was recently in the news after questioning how Humza Yousaf's initiative of providing monthly and annual season-ticket holders with a “free week” was to be funded.
Mr Verster had previously said:
“We are working with the Scottish Government to understand how to fund the £3million."Reports suggested that the Scottish Government want to fund the initiative by using a railway improvement fund - which has been earmarked for other projects. The fund was estimated to be worth around £1 million. It is thought the Scottish Government wanted Scotrail to pay £1.8 million towards the "free week".
You can read our previous story here.