Gloucestershire County Council says it needs around £52 million a year to maintain roads, bridges, street lights, traffic lights, drainage and pavements to the standard residents expect.
Current government funding is around £36.5 million a year, leaving an estimated annual shortfall of £15.5 million.
Cabinet member for highways Councillor Mark Harris described the gap as a “black hole” in road funding.
The council says highways teams are continuing to prioritise urgent repairs and keep the network safe.
An extra £15 million has been allocated over the next three years from council savings and efficiencies to support road repairs.
Residents are being encouraged to report potholes and other defects through FixMyStreet.