Reigning UK National Hill Climb champion Harry MacFarlane has taken the joint Strava KOM on what is claimed to be San Franciscos steepest street, matching a time that hasn't been bested since 2011. The British rider tackled Green Street a frighteningly vertiginous ascent with gradients reported to average around 41% matching a long-standing time set in December 2011 by Brooks Sizemore. Read more: What is the steepest road in the UK? Plus 6 more gruelling climbs According to his uploaded data, MacFarlane hit a peak power of 1,252W, averaging 878W for the 21-second effort. Commenting on Strava, he summed up the ride: 41% is fu*king wild. San Francisco is no stranger to extreme gradients. A commonly cited 2016 article claims the top 10 steepest streets have an average gradient of at least 31%. MacFarlane retained his UK National Hill Climb Championship titles in 2025 with a record-breaking run up Matlocks Bank Road, producing an extraordinary 707W average and a peak power-to-weight ratio of 9.9W/kg. Read more: A 4.8kg bike and 9.9W/kg: 6 remarkable numbers behind Harry MacFarlanes National Hill Climb Championships win