The Hertzog Bridge over the Orange River at Aliwal North will be closed for a minimum of two weeks.
According to Eastern Cape Transport officials, it could be longer as steel needed to repair the structure has to be imported.
Eastern Cape Transport Department spokesperson, Tsepo Machaya, says the bridge was damaged when a truck went out of control and crashed on Saturday.
No one was injured in the incident but the damage is expected to run into millions of rands.
Motorists coming from Port Elizabeth should go via Cradock, Middelburg en then up to Colesburg to the N1.
Other Alternative routes include:
Aliwal North, Sterkspruit, Zastron, Rouxville.
Burgersdorp, Venterstad, Gariep Dam, N1.
Burgersdorp, Venterstad, Bethulie, Smithfield.
