Uber tripled its fares in London for this reason by Benjamin Snyder @FortuneMagazine July 10, 2015, 10:12 AM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons A strike of London’s Underground workers Thursday led to Uber, maybe unsurprisingly, tripling its fares due to high demand. The ride-sharing service’s surge pricing kicked in during the strike, going as high as three times the typical fare for a ride. Uber defended the London price hikes, saying its pricing policy is fully transparent. “Drivers work on the Uber platform on a completely flexible basis, as much or as little as they want,” Uber said in a statement to Quartz. “During times of peak demand … fares increase temporarily to incentivise more drivers to work on the platform.” Still, those on social media were quick to complain about the incident. Nice to see @Uber are cashing in on the #TubeStrike 😡 #Uber with triple times the price of the normal journey!!! http://t.co/oiq6r2EnTy— Mikey Phillips (@MakeupbyMikey) July 09, 2015 Disappointed with the @UberUK price surge during the #TubeStrike #playnice #uber – shortsighted strategy in place there! — Emma McGowan (@lets_workbetter) July 9, 2015 To help with transportation in the city, London made additional buses, bicycles, and riverboats available, Quartz reported. About 4 million take the Underground in London each day, CNN said. In the past, Uber has suspended surge pricing for certain events, including a New York City blizzard in January. Subscribe to Data Sheet, Fortune’s daily newsletter on the business of technology.