In winter months, urban activists and designers have been known to observe where people drive and walk through snow, then use that information to redraw streets and sidewalks. But this year, one Toronto resident didn’t wait for “snowy neckdowns” (or: sneckdowns) to see if he and his neighbors could test safety measures at a local intersection.

So David Meslin gathered a group to create a set of temporary curb extensions. The main ingredients: a one-to-one ratio of cornstarch and water for the solid white lines plus leaves from area yards. The guidelines helped direct cars while leaf piles visually reinforced them, encouraging vehicles to follow a modified path. This soft “leafy neckdown” redesign didn’t prevent anyone from driving over the lines or through the leaves, but reshaped traffic behavior nonetheless.

“Last week I got together with some neighbors,” Meslin explained in a social media post, “and we temporarily re-designed a dangerous intersection near our homes. Using only chalk and leaves (and maintaining all existing road widths at 28 feet) we revealed a surplus surface area of 2,000 square feet which could be transformed into a parkette, new sidewalks, and much shorter/safer crossings.”

The idea behind these kinds of changes is relatively simple: if cars don’t need the space, why give it to them? Narrower roads (that are still sufficiently wide for vehicles) tend to slow cars down and reduce crossing times, making things less dangerous for pedestrians. And, of course, that freed-up space can be put to better use, too.

Guerrilla interventions like this may be impermanent, but they can help highlight areas for potential improvement and illustrate how easily cars can adapt to small changes on city streets. Of course, not all municipalities will take kindly to this type of citizen action — stay safe!