Flat land helps; see Davis, CA. Now try that in wide swaths of San Francisco: http://maps.google.com/maps?q=22nd+st+and+rhode+island+&hl=en&ll=37.75426,-122.40

Flat land helps; see Davis, CA. Now try that in wide swaths of San Francisco: http://maps.google.com/maps?q=22nd+st+and+rhode+island+&hl=en&ll=37.75426,-122.401578&spn=0.009857,0.01929&sll=37.0625,-95.677068&sspn=40.052282,79.013672&z=16&layer=c&cbll=37.753334,-122.401107&panoid=mCWNoN_KpD5p3WE9NygDDQ&cbp=12,339.65,,0,0.5 http://maps.google.com/maps?q=22nd+st+and+rhode+island+&...