Six "bat bricks", which have holes to allow bats access into buildings, are to be incorporated into the structure, work on which began in November and is scheduled to finish in May.
The project, loosely based on the famous steam engine Mallard which held the world speed record, has excited criticism since Mach, 40, unveiled his plans last year. But the news that it is coming with flying mammals has brought unfavourable comment to a new pitch.
"I shudder to think what might happen," said Durham County Council's Peter Jones, who has protested to Darlington's environmental health department that the presence of bats close to Morrison's supermarket represents "a crazy health hazard".
"Shoppers will be sharing their trolleys with blood suckers swooping down on their groceries. It is the logic of the madhouse."
A spokeswoman for Morrison's, which commissioned the sculpture, rejected the criticism: "The Brick Train is more than 300 yards from our store and we are satisfied that's far enough away not to pose a problem."
Mach was "non-plussed" by the fuss. "Bats are tiny nocturnal creatures and they're not going to bother anyone. I'm sure they'll have better things to do."Reuse content