GENIUS…Line a pathway with rocks painted in glow in the dark paint. During the day they “charge” in the sun and in the evening they reflect the stored light. Rust-Oleum Glow in the Dark Brush-on Paint.
Other simple-to-install options that work especially well for decks include banister cap lights, rope lights and downlights built into the posts. Most of these accessories are easy to find, and retrofitting an existing deck stairway should be relatively easy.