Up to 60,000 people are expected to take to the streets in Lewes next weekend for the East Sussex town's annual bonfire event.
Sussex Police said official numbers had never been established but the figure was an estimate of the size of the crowd that could attend on 5 November.
About 400 police uniformed officers will be deployed. Plain-clothed officers will also be on patrol.
Six bonfire societies will take part in more than 30 processions on Saturday.
The main procession, The United Grand, will see most of the societies marching together.
At the end of the event, six bonfire and firework displays will be held at various locations around the town.
Supt Tony Blaker said: "The Lewes Bonfire continues to be an incredibly popular event, the policing of which involves months of preparation, planning, consultation and enthusiasm for what is the biggest annual policing commitment in East Sussex."
He added: "Sussex Police support the right of Lewes residents to hold this event but due to sheer numbers and the disruption locally, we would encourage the wider Sussex community to attend bonfire events closer to where they live."
He said the force had worked with the bonfire societies and district council as well as other organisations to minimise disruption.
Last year, about 20,000 people arrived in Lewes by train.
He advised people to plan their visit in advance because there would be "considerable delays" on rail services and restricted road access.
Any cars parked in contravention of road closure orders would be removed, he added.
Stewards and information points would be available, he said.
Visitors are urged to find a place to watch the processions and not to try to follow them into crowded areas.
People are also being told not to bring glass bottles, or drink to excess, or let off fireworks and bangers, for safety reasons.
Lewes Bonfire Council has posted a map of routes and road closures and advice for visitors on its website.