Any street or cycletrack or part thereof constructed under this Act when completed shall be maintained by and at the expense of the highway authority unless it has been agreed in writing between the Authorities and the highway authority that it is to be part of the bridge.

Where a street is widened, altered or diverted under this Act, such part of the street as has been widened, altered or diverted shall when completed be maintained by and at the expense of the highway authority unless it has been agreed in writing between the Authorities and the highway authority that it is to be part of the bridge.

This section shall not apply to any street or part thereof which is part of the bridge.