“It’s yellow, it’s ugly, it doesn’t go with anything, but it can save your life.”

That message, written in French next to an image of the designer Karl Lagerfeld dressed in black tie and a Day-Glo safety vest, was plastered around Paris in the late aughts as part of a government bicycle safety campaign.

Sarah Canner, an American actress and writer with an equal interest in fashion and bicycles, was living in the city then and liked the poster but took issue with the basic premise.

Yellow? Ugly? Why?

Envisioning a wardrobe that would look as good on the bike path as on the runway, Ms. Canner returned to New York, where she started Vespertine NYC, a line of fashionable bike clothing and accessories woven with 3M Scotchlite reflective accents.

Forget pedal reflectors. Her frock dresses, tweed scarves and blossom brooches light up at night like a Broadway marquee.