For cyclists, Phoenix is a hostile place. It's frequently ranked one of the most dangerous cities in the nation for bicycles, with its giant boulevards, poor bike infrastructure and urban sprawl. But every so often, a group called Critical Mass Phoenix takes to the streets. With Critical Mass, dozens, sometimes hundreds, of Phoenix cyclists ride together, often down Central Avenue, taking over the streets themselves. These rides usually happen at night, starting at sunset. Cyclists wear fluorescent orange and yellow; some attach colorful lights to their bikes. Critical Mass is a nationwide movement dating back decades, but its nighttime Phoenix rides are a sight to behold — a reminder of the power of collective action, even in a car-centric desert city like Phoenix.