Travel centers should build a balanced reader-and-sunglass program, then let location-level demand decide which category receives more depth.
Readers
Protect core powers for receipts, phones, paperwork, maps, menus, and replacement needs.
Sunglasses
Use broadly wearable driving styles and increase depth before holiday and road-trip peaks.
Display size
Countertop works for lower-volume or space-constrained locations. Floor works where traffic supports fuller reader breadth and sun choice.
What decides expansion
Track units, power stockouts, sun sell-through, reorders, and seasonal travel patterns.