"When a car goes by, perhaps we can invite them to join us for a cup of tea on our balcony," one resident told a newspaper, opting not to be named.
Faced with widespread criticism of the project, Transport Minister Kamel al-Ouazir told a public television channel: "We can't sacrifice the interests of the whole governorate just for one, two or ten apartments."
The flyover is being built to link the northern and southern sectors of Cairo's Giza district, on a route to be used by an estimated 750,000 cars a day.
The minister said the bridge was crucial for the governorate's infrastructure and would also link up with a train station, the construction of which has been in the pipeline for several years.
A ministerial committee would offer compensation to residents who insisted on moving, but there was "no alternative" to the project going ahead, said Ouazir.