Swedish designers have created the world’s first “invisible” bike helmet.

Industrial Design students Anna Haupt and Terese Alstin came up with the idea when Sweden introduced the country’s first mandatory helmet law. They wanted to develop a safe bike helmet that people would be happy to wear, without the bulky discomfort of conventional helmets.

The pair spent seven years studying bike helmet reports, enlisting help from head trauma specialists, and staging bike accidents with crash test dummies and stunt people to study the movement patterns of different collisions.

“We had to simulate all known accidents,” Alstin said. “Everything from an icy road crash to getting hit by a car.”