Games : Howto fix a broken/interrupted Bus line?

I have placed a Bus terminal and a route through my city.

Unfortunatley, this line is 'broken'/'interrupted' at some point.

How can I fix such a broken line?

I can't find a possibility to 'extend' the existing line or 'add' the missing piece.

I'm not sure about this:

Does a broken Bus line work at all?