Mark Brader wrote:
John Rowland:
Since double-decker buses aren't the easiest things
to turn around, except at authorised turnarounds

Mark Brader:
They aren't? Wouldn't it just be a matter of going
"around the block" via suitable side streets?

John Rowland:
Yes, but most side streets and corners here aren't suitable. ...

In what way?

The roads are too narrow and / or crowded with parked cars., There might
also be overhanging trees.