A vest works when drivers and machines can see the wearer early. Check stripe area, placement and condition — not just brightness.
Look at stripe coverage first: wider, well-placed stripes around the torso read earlier than a thin trim. Full-coverage styles put reflective area on the front, back and sides.
Check the vest in low light before ordering in bulk. A quick sample check at dusk tells you more than a catalogue photo.
Plan for washing: reflective stripes wear with washing. Ask the supplier how the style holds up after washing, and keep spares so faded vests are replaced, not kept in service.