“Ghost bikes,” riderless and painted white, were placed at two busy intersections in Portland, Ore., last October, makeshift memorials to two bicyclists killed when they were hit by trucks in accidents that month.

This spring, at those same intersections and at 12 others across the city, “bike boxes” will be laid out on the roadway to provide a clearly designated place for cyclists, in front of and in full view of drivers, to wait for traffic lights to change. The boxes will be marked with signs and wide stripes alerting drivers to stop behind them at red lights.

Portland, which has a higher percentage of people who bike to work than any other large American city, is already considered one of the country’s most bike-friendly urban centers. But the boxes, believed to be the first such to be put to use by any city in the country, will make cyclists even safer and more comfortable on the street, biking advocates and transportation officials say.

“It’s something the city has been talking about for a long time, but these two deaths have certainly given an added sense of urgency,” said Jonathan Maus, whose bikeportland.org is a focal point for Portland cyclists. “The community has just made it so clear that this is very important, that they’re very concerned following these fatal crashes that things need to change.”