A massive mobile Wi-Fi network that could be a model for many cities was launched in the city of Porto, Portugal, this fall. Buses and taxis are equipped with routers that serve as mobile Wi-Fi hot spots for tens of thousands of riders. The routers also collect data from the vehicles—and from sensors on trash bins around the city—and relay it back to city offices to help with civic planning. More than 600 buses and taxis are part of the network, which is now serving 70,000 people a month and absorbing between 50 and 80 percent of wireless traffic from users who otherwise would have had to use the cellular network. Built by a startup called Veniam, spun out of the University of Porto, it is the largest and most sophisticated vehicle-based network in the world, the company says.