Council bosses have brought in special measures to ensure bus pass holders can still travel despite a delay in issuing new cards.
A national concessionary scheme is being introduced from 1 April, which requires thousands of new passes to be distributed throughout County Durham.
But Durham County Council says it has been hit by delays in distributing thousands of new passes.
It has assured passengers that old-style passes can still be used.
A Durham County Council spokesman said: "The new concessionary bus fare scheme allows anyone over the age of 60 or who has a disability, free travel on local buses anywhere in England.
"Councils have been issuing the new-style passes that are required by the scheme, but in some areas, including parts of the North East, delays at the national pass supplier are affecting the issue of new passes.
"To overcome this, and until the new passes become available, local authorities throughout the region have agreed with bus operators that the old style passes issued in these areas will be accepted for free travel throughout Tees Valley and Darlington, Northumberland, County Durham and Tyne and Wear during April."