Lombard Street (San Fransisco)

The switchback's design, first suggested by property owner Carl Henry and instituted in 1922, was born out of necessity in order to reduce the hill's natural 27% grade, which was too steep for most vehicles. It is also a serious hazard to pedestrians, who are accustomed to a more reasonable 4.86° incline because of wheel chair navigability concerns. The crooked section of the street, which is about 1?4 mile (400 m) long, is reserved for one-way traffic traveling east (downhill) and is paved with red bricks. The speed limit in this section is 5 mph (8 km/h).