Read this: Cycling is popular in Tucson due to its flat terrain and dry climate. Tucson and Pima County maintain an extensive network of marked bike routes, signal crossings, on-street bike lanes, mountain-biking trails, and dedicated shared-use paths. The Loop is a network of seven linear parks comprising over 100 mi (160 km) of paved, vehicle-free trails that encircles the majority of the city with links to Marana and Oro Valley. The Tucson-Pima County Bicycle Advisory Committee (TPCBAC) serves in an advisory capacity to local governments on issues relating to bicycle recreation, transportation, and safety. Tucson was awarded a gold rating for bicycle-friendliness by the League of American Bicyclists in 2006.

Why is cycling popular in Tucson?
What is the answer? (If it cannot be answered, return "unanswerable")
its flat terrain and dry climate