A broken level crossing at Pevensey is causing long traffic delays.
Eastbourne Road is blocked in both directions at the level crossing by Pevensey and Westham railway station after it became stuck in the down position.
According to an eyewitness, it has been broken for more than an hour.
According to a Network Rail spokesman, the level crossing barriers went down at 5.30pm.
There are currently teams on site working to fix the fault, and someone is en-route to manually operate the barriers to ease the gridlock.
However, due to the A27 being closed in Lewes this afternoon, the staff member has been delayed. They were expected to arrive at the crossing within 15 minutes, but it would take them a while to set up the equipment to manually control the barriers, a spokesman said.
Trains are delayed by between eight to 10 minutes due to the incident, they said.