SG,
You are correct, 125th is an arterial. The best two options for getting to LC way are either 125th or 145th. Taking away a lane of traffic will likely shift more cars to 145th, increase congestion there.
Adding a bike lane to 125th is a foolish decision IMHO.

They recently did the same thing on westbound 130th between Aurora and Greenwood. In the afternoon, the place is a complete cluster. One lane now ends abruptly, replaced by a bike lane. Folks are now forced to turn right or get over quickly into the now single through lane. I've seen several accidents and many near misses since they put in the bike lane.
I find it hard to see the benefit of removing an arterial lane of traffic for a bike lane that is about a total of about eight blocks long.....