You could say children had to die for the change to happen

The Netherlands.

You're thinking - bicycles! So what's the deal? How did the Netherlands get their infamous bicycle infrastructure?

It might interest you to know that they had the same pressures as most parts of the world to re-align their infrastructure to favour cars. But the people protested when things got out of hand. They eventually convinced the government to change transportation policy to change things to accommodate bicycles. The rest is history.