Helsinki, on the southern shore of Finland, has a regional population of 1.2 million. Its transportation options include buses, trams, and a metro, not to mention bike rentals in the summertime—yet plenty of people still use cars. To encourage more of those drivers to use public transportation, the local government is working with a local tech company’s smartphone app. Called Whim, the app lets people combine public transit with car rentals, ride sharing, taxis, and…