The government has said mourners will not be able to stop to pay their respects after they have queued to see the Queen lying-in-state.
Hundreds of thousands of people are expected to travel to London to visit the Queen's coffin in Westminster Hall before the funeral on Monday morning.
The public viewing opens at 5pm on Wednesday, and will be open 24 hours a day until 6.30am on Monday September 19 – the day of the Queen’s funeral.
Whitehall officials have worked out a 10-mile route for mourners to queue, with warnings they could wait up to 30 hours before they see the coffin.
Security will be tight, with visitors warned they will have to pass through airport-style security.
However, once mourners are through security and in Westminster Hall they will not be able to stop and will be told they must file past in a constant queue before exiting the Hall.
The system will be similar to that in Edinburgh, where mourners queued overnight to walk through St Giles' Cathedral earlier this week to pay their respects.
The queue route will stretch from Victoria Tower Gardens, across Lambeth Bridge, down to Westminster Bridge - before veering down Belvedere Road, through Jubilee Gardens, to South Bank, and along to the Tate.
The Queen's coffin arrived at Westminster Hall on Wednesday afternoon, where a solemn, 20-minute service was held upon its arrival.
The service was led by the Archbishop of Canterbury who was accompanied by the Dean of Westminster.
The procession left the palace at 2.22pm and arrived at Westminster Hall at 3pm.
The King, the Prince of Wales and the Duke of Sussex followed the coffin on foot as it made its journey to parliament for the lying in state.
The Duke of York, the Princess Royal and the Earl of Wessex walked behind them.
Princess Anne's son, Peter Phillips, and her husband, Vice Admiral Sir Timothy Laurence, also joined the procession - as well as the Duke of Gloucester and the Earl of Snowdon.
The Queen Consort, the Princess of Wales, the Countess of Wessex, and the Duchess of Sussex travelled by car.
Watch: Public queue for late Queen's vigil in Edinburgh