I wouldn’t recommend cycling down Sabys Road AT ALL. I avoid for my own safety, too many near misses. It’s a horrible road with fast cars and blind corners. Cyclists of all levels should avoid it.
Not sure where you are starting from to provide a perfect route.
To avoid Sabys, I’d cycle North up Quaifes, then Fountains and Hodgens Road (the West portion of Whincops can be busy, so avoid that too)
This comes out onto a busy section of Springs for a few hundred meters, but the road is wide enough to keep to the side (in my opinion), but could be unnerving for beginners / family groups

Once the Nor’ West Arc cycleway is completed ( mid 2021 ? ) the Quarrymans’ Trail will link to the Little River Link cycleway at Annex Road. Sparks Road , north to Centennial Park through to Lincoln Road via Domain Terrace.

https://ccc.govt.nz/assets/Images/Transport/Cycling/Updated-NorWest-Arc-map.PNG

My current pick is to use Sabys and Trices roads, but with the concern that this may prove to be a ‘short cut’ route for drivers between Halswell and Prebbleton. Ellesmere Road would be a more natural line to take, but it’d involve a long passage on a road as opposed to paths.

(You can, of course, simply travel north while still in the city proper until you hit the LRT, but that way you’re forced to travel a very wide arc many kilometres longer than more coming across the southern part of the city.)

Anyone riding this at night should absolutely have decent lights, which make the darkness much more rideable. The legal minimum is anemic. and there’s a raft of excellent lights available. Plus we’re going into summer now, so ~6 months of long late evenings.