Officers are investigating after a vehicle collided with railway crossing barriers this morning, before driving off, police said.
The A29 is closed between the Rowan Way roundabout and Westergate after damage to the Woodgate level crossing.
Trains are moving slowly through the area while the problem is being fixed.
A spokesman for British Transport Police said: “At 7.08am today officers were called to a level crossing on Westergate Street in Aldingbourne after reports a vehicle collided with the barriers causing damage.
“The vehicle then failed to stop at the scene of the collision.
“Engineers form Network Rail also attended to make repairs to the level crossing.
“Enquiries are now being made in relation to this incident in order to trace the person responsible.
“Anyone with information should contact BTP by texting 61016 or call 0800 40 50 40 quoting reference 98 of 10/08.”