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.
話が横道にそれてしまった。
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.