What is the Radroute bicycle path?

What is the Radroute bicycle path? - Man Riding Bicycle on Road

I've seen signs (like the one below in Southern Tyrol) in street view of "Radroute" bicycle paths around Germany but haven't been able to find any information in English. The signpost below seems like it is part of a decent bicycle path going for at least 50km. What is Radroute?

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Pictures about "What is the Radroute bicycle path?"

What is the Radroute bicycle path? - Man Riding Bicycle on Off-road

What is the Radroute bicycle path? - Black and White Hardtail Bike on Brown Road Between Trees

What is the Radroute bicycle path? - Bicycle Lane on Gray Concrete Road

Adda Ciclovia | Bicycle path | Radweg | Da Tirano a Milano | 160 km

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Images: Andrea Crabbi, Mike, Philipp M, Pixabay