context: San Diego's roadway system provides an extensive network of routes for travel by bicycle. The dry and mild climate of San Diego makes cycling a convenient and pleasant year-round option. At the same time, the city's hilly, canyon-like terrain and significantly long average trip distances—brought about by strict low-density zoning laws—somewhat restrict cycling for utilitarian purposes. Older and denser neighborhoods around the downtown tend to be utility cycling oriented. This is partly because of the grid street patterns now absent in newer developments farther from the urban core, where suburban style arterial roads are much more common. As a result, a vast majority of cycling-related activities are recreational. Testament to San Diego's cycling efforts, in 2006, San Diego was rated as the best city for cycling for U.S. cities with a population over 1 million.
question: శాన్ డియాగోలోని పాత పరిసరాలు సైక్లిస్టులకు ఎందుకు ప్రసిద్ధి చెందాయి?
answers: the grid street patterns