side street; byway; cross street
A smaller street branching off from a main road; often implies a narrow or less-traveled path.
When we turned off the main street into a side street, it suddenly became quiet.
digression; straying from the point
Figurative use for going off-topic in conversation or thought; often used in phrases like 横道にそれる.
The conversation digressed.
The discussion ended up straying off topic.
If you turn off the main street by the station into the side street, a quiet residential area opens up.