Why the lid is round?

Question

why the lid normally at roads and streets for sewerage are round in shape.

Answer 1

A round lid is the only shape that can not be positioned to fall through the hole in the pavement.

Answer 2

went for a walk in our neighbourhood all ours were square and hinged at the curb for the sewage or storm sewers did not notice any round ones but because of the snow and ice  on the road the sewers had steam coming from them easy to spot the round ones are more in the middle of the road they may be for other stuff like phone cable access or hydro access call you local utilities to see want there answer is

Answer 3

They ran out of square ones.

Answer 4

Because that's the shape that makes it impossible for the cover to fall through the hole.

If it was square you could tilt it diagonally and get it through.

Answer 5

because the people who go down them are round shaped

Answer 6

Because it is geometrically impossible for a round lid to fall through the round flange it normally sits on.  A square lid can indeed slip though diagonally.

Answer 7

Because it will displace the weight of anything going over it to be more evenly distributed,and therefore less chance of a collapse.