Thousands of London Underground staff, including drivers, have voted to go on strike in separate disputes over staffing, safety and industrial relations, according to the RMT union.
Transport for London's chief operating officer for London Underground Steve Griffiths said: "Our staff work hard to serve the millions of customers that pass through the Tube and rail network every day.
"Everyone has the right to go about their work without fear or intimidation and we do not tolerate any form of verbal or physical assault on our staff.
"Our campaign against workplace violence sends a clear message that any assault on staff will be fully investigated and we work closely with the British Transport Police to bring perpetrators to justice.
"If you ever witness an assault on a station staff member, you should report it immediately so that we can all work together to maintain a safe transport network."