Hi Clara,
123rd is incredibly steep.
There's this kind of hidden route that shows up on Strava. It's slightly shallower.
I prefer 112th via 113th/Exeter, 97th, or 93rd/94th (small entrance, but well used).
If nothing else they could be excuses to improve crossings of Sand Point Way at 106th, 97th and/or 95th at 45th
I can send specific routes if any of these sound interesting. I'm pretty sure my wife's preference is 97th.
Connecting Roosevelt to Northgate (5th Ave) is difficult because of the steepness.
Cutting through the parking lots at 108th is shallow, but I'm guessing that won't happen b/c private property.
105th is a one-lane road with a brief steep part that could work if completely closed to cars,
but it also feels somewhat sketchy like you're riding between a blank wall and the beaver pond.
103rd is very steep up/down, but it goes by a nice P-Patch, makes a direct connection to the transit center.
The curb ramps at 103rd/5th corner should be redone if nothing else. I think 103rd is also 2-way but "do not enter",
so if the budget is like $10 it's one of the places an 'except bikes' would help if only for advanced or ebikes (and a wayfinding sign at 103/Roosevelt).
I haven't seen what's happening w/ 8th, but that may have more potential for AAA access to Northgate.
115th or 117th are both already pretty calm (I prefer 117) There's a steep ridge in Victory Heights that you can see if you turn terrain on,
but this route avoids the worst of it and only uses a block of 125th. Of course there are variations of this route that use Pinehurst Way and 125th,
but this would be an excuse to make 8th (which has a lot of apartments) a slower street w/ speed cushions and to slow 115th or 117th more,
Were you thinking of PBL's on 130th from Aurora and 5th for access to the 130th station (if that's happening?)
Both of those would be huge wins and very useful.
Hope some of this helpful.
-Tim