Abstract: This curvy block is an American icon that attracts tourists from around the world. Hundreds of hydrangeas and flawlessly groomed shrubs bring a vibrant look to the road that is rarely found on city streets.
How It's Unique: San Francisco's most recognizable street originally had a 27 percent grade, making it too steep for the first automobiles to conquer. In 1922, the eight curves were added, reducing the grade to 16 percent.Lombard Street was a two-way road until 1939.
Read more: The World's 18 Strangest Roadways: Gallery - Popular Mechanics
Abstract: As designed, the large outer circle is a two-way road, which could result in significant congestion. However if the outer circle were converted to just counter-clockwise, this would be a true TCI, and likely be extremely efficient. No plans for this, but it is a "Sustainable Design" because it can easily be converted to one-way operation.
