Traffic was redirected after a lorry collided with some scaffolding near the level crossing in Portslade this morning.
Brighton and Hove Police said in a tweet: "We are dealing with an incident near to Portslade rail crossing where a lorry has hit some scaffolding.
"Please follow officers directions and seek alternative routes. No traffic is able to pass at the moment."
A spokesman from Brighton and Hove Buses said: "Due to an incident by Portslade Station, our BH6 and BH46 services cannot serve the stop.
"The 46's are diverted via Olive Road in both directions. The 6's are diverted via Station Road, the seafront, Trafalgar Road and Old Shoreham Road in both directions."
Police confirmed the incident had now been cleared.