MEDFORD, MA — Two more "three-dimensional" crosswalks were unveiled at schools in Medford Monday. The optical illusion, designed to look like floating blocks in the middle of the road, was recently installed at the McGlynn School and the Columbus Elementary School. There are now 3-D crosswalks outside four elementary schools in Medford.

The first design was painted outside the Brooks Elementary School over April break and replicated two months later outside the Roberts Elementary School. Officials said similar designs have been effective in lowering speeds in other cities.

The idea was first proposed by Isa and Eric, two students at Brooks, who spoke before the Traffic Commission last year. They came up with the idea after Eric's younger brother was almost hit by a car near the school.