Thousands of people from Brighton and Hove are heading to Lewes for the annual bonfire night celebrations.
Road closures in the town from 3pm are expected to lead to traffic jams along the A27, including for people heading home from work in Brighton.
Train company Southern said that it would be running a normal scheduled service to and from Lewes but warned: “Evening trains via Lewes will be very busy indeed.”
Southern said: “Cycles will not be permitted on Southern services after 4pm between Brighton and Eastbourne.
“A queuing system will be in place at Brighton, London Road, Moulsecoomb, Falmer and Lewes stations from early evening until the end of service.”
The last train from Lewes to Brighton leaves at 11.55pm.
A mass cycle ride is due to leave The Level in Brighton for Lewes via the Sussex University campus at Falmer.
Those taking part are gathering from 5.30pm for a 6pm departure. About 200 cyclists are expected to form a bike train which will snake up Lewes Road.
More will join at Falmer House on the university campus.
The organiser Duncan Blinkhorn said that the bike train would be highly visible with lights, flags and triangle warning signs at the rear.
They will be accompanied by experienced stewards and mobile mechanics while cycle-mounted sound systems will power the music including classics such as Arthur Brown’s Fire.
The return rides will leave from outside Lewes Prison at 11pm, midnight and 1am.
Mr Blinkhorn said: “We organise bike trains to various events throughout the year to make it safer and more fun for people to cycle.
“This is our fifth bonfire ride to Lewes. It is always hugely popular, bringing light and laughter to the Lewes Road, especially the incredibly dark narrow cycle path beyond Falmer to Lewes.”
Sussex Police Assistant Chief Constable Robin Smith issued the force’s annual plea for people to celebrate bonfire night closer to home rather than head to Lewes.
He said: “Our priority is to keep the public safe. Each year thousands of people attend the Lewes bonfire celebrations. It’s one of the biggest in the country.
“Both Sussex Police and British Transport Police work closely with Lewes District Council, the bonfire societies, East Sussex Fire and Rescue Service, South Coast Ambulance, St John Ambulance and the Red Cross to assist the public and minimise the risk of crime, disorder and any injury.
“As always I’d like to remind all that this event is meant for the residents of Lewes and the wider Sussex community should visit bonfire events closer to home.
“This event is not suitable for children and pets.
“Finally, please do enjoy the night but do so responsibly. The throwing of fireworks in the street is dangerous, will not be tolerated and will be dealt with robustly.
“What we all want is a safe and enjoyable event.”
