Some mornings when you're driving to work or school, it feels like every traffic light is red — the lights are never green when you want them to be! But some commuters in the Danish capital of Copenhagen have a different experience. Traffic light after traffic light is green as you travel into the center of the city — as long as you're riding a bicycle. This is called the "green wave," and it's designed to help cyclists get into the center more quickly. Here's how it works. Traffic lights are synchronized so that a cyclist traveling at 20 kilometers per hour will get a series of green lights. There are little LED lights on the ground on some routes that tell cyclists they can expect a green light ahead. This is not a new system in Copenhagen. The idea is actually more than 20 years old, but it's now set to be expanded to more routes around a city that's been called the most bike-friendly in the world. In the early years of the "green wave," it was shown to cut travel time for cyclists by 17%. In the morning, the lights are synchronized to prioritize people going into the city, while they're synchronized to help people get out of town faster at the end of the day. But the green wave is not perfect. Some people cycle too fast to benefit from the synchronized lights, while others don't pedal fast enough. This is also a problem during rush hours, when there may sometimes be so many bikes that it's just too busy to cycle at 20 kilometers per hour, according to some residents. Plus, if cyclists are favored at traffic lights, buses sometimes get stuck on red lights and take longer to get to their destination. However, the aim of the green wave is clear: make it easier for people to leave their cars behind and travel in a greener way.