On normal main roads with 2 way traffic with ample clearance 30mph seems fine. The problems arise down these side residential streets, with cars parked both sides, where 30, to me, seems excessive.
These streets wern't designed for the mass parking we see now.

In the past these type of roads did reduce speed by default but these days seems to make no difference and 20 has to be enforced.

At the moment you can often hear vehicles approaching but as more electric vehicles take to the road problems will increase.

Policing this speed reduction is another matter though.

Satnav:
Garmin DS61 LMT-D (In the car)
Garmin 2599 LMT-D (Indoor test rig)
DashCam:
Viofo A119 V3