A £1.5m police custody suite is being officially opened at Crawley police station.
The 26-cell facility, described as "state-of-the-art", replaces an old custody suite which had 18 cells.
Sussex Police said airport expansion at Gatwick and increasing arrests by the joint border operations centre had put pressure on Crawley.
Previously, when Crawley was full, frontline police had to drive detainees to vacant cells across Sussex.
The new cells have natural light, different levels of benches, toilets and intercom systems.
Assistant chief constable Nick Wilkinson said: "The new cells are a much-needed facility in the north of the county and provide a vastly improved environment for detainees and staff alike."
He added: "A visit to custody as a detainee can be an unnerving experience and it should be remembered that everyone who comes in has yet to be charged with any crime.
"Whatever the eventual result of their visit, it is important that they are treated with care and with dignity and the new facility goes a long way to meeting this requirement."
He said the extra capacity would also allow police officers to remain local and return to their frontline duties more quickly.
Last year, Sussex Police managed approximately 45,000 detainees in 126 cells across six custody suites.