As opposed to a pannier, because the pack rides higher, there's less mud to carry into your workplace. Your back stays warmer so you need less clothing on your torso. You'll need to establish a weight limit so you can safely handle the bike esp. in windy conditions or on unexpected swerving.

For biking, the pack needs to work harder

1. Weatherproof cover
2. Smaller flatter profile, weighing 1-2lbs
3. Fit your shape with a chest or hip strap to stabilize the load