The portion of Route 4 between Jefferson/23rd and MLK/Plum is duplicative of routes 8 and 48, which currently run at a much higher frequency. The other part of Route 4 is the exact same as Route 3.
A possible solution is to discontinue Route 4, and run Route 3 at 15-minute frequency. The former Route 4 riders could transfer between Route 3 and routes 8 or 48. This would also reduce confusion along the shared 3/4 corridor.