While it is better than nothing I think you need more material for good visibility in the dark. I also think you really want retroreflective materials.
If you are walking in a low speed residential area with sidewalks it is probably fine, but for higher speed areas, or areas without sidewalks I'd strongly consider a lot more material.
For reference, note ANSI rates safety vests. IIRC, the ratings inform what speed traffic the various vests are appropreate for.
-john