On what basis is it decided that a Flyover bridge will be suitable to solve the traffic problems or a Subway?

Question

On what basis is it decided that a Flyover bridge will be suitable to solve the traffic problems or a Subway?

Answer 1

It worked in Star Trek.

Answer 2

On the basis of,if it is to be made for the vehicle or for the people.

Flyover bridges are never made for the walking crowd and Subways are never made for the vehicles

cheers,

Answer 3

On a traffic engineering basis, performed by well-educated traffic engineers.

Answer 4

Stop the vechiles on flyover bridge.and close that road then it will slove the traffic problems