A non-straight route

Solution 1:

I would describe the route as roundabout. "That bus takes a roundabout way to get there. It's much more direct to take route X".

Solution 2:

I would say circuitous, meandering, serpentine, tortuous, sinuous or labyrinthine. Roundabout is more common, but less fun!

Solution 3:

You could say it's a local bus instead of an express bus, meaning that it makes a lot of stops along the way; or you could say that its route is too indirect or too winding, meaning that its path meanders all over the city instead of making a beeline for the destination.

Solution 4:

In informal British English, I'd say the indirect bus goes round the houses.

Solution 5:

In middle-America the colloquialism "goose chase" is used to describe this. "Goose chase" is also a type of stitching pattern used in quilting because it has the same meandering property.