Mass transit has made a rebound with the return of city life post-Covid 19, and today a startup that's building tech to help it run more smoothly is announcing a big round of funding to meet the rush. Optibus, which uses AI to help public transportation bodies and their mass transit partners plan and operate their networks, has raised $100 million, funding that it will be using to continue expanding its product set and wider business footprint, CEO and co-founder Amos Haggiag said in an interview in London this week.

The Series D funding values Optibus at $1.3 billion, which the Israeli startup says makes it the first "unicorn" in the public transportation tech space.

Insight Partners, Bessemer Venture Partners, Verizon Ventures, Pitango First & Pitango Growth, Tencent, SOMV Momentum are among the investors in this round, which is brings the total raised by the startup to $260 million and is coming about 14 months after Optibus raised $107 million in a Series C at a $400 million - $500 million valuation.

That's a big leap, but in a period where a lot of growth-stage startups have found it a challenge to raise more money, Optibus stands out as an example of how the right mix of timing and traction can still close deals.

The company now has customers in over 1,000 cities, double the number of a year ago; and its employees have also grown to 300 (up from 120). In total, Optibus is being used to track and power about 2.5 billion trips on buses, on-street trams, light rails and subways annually around the globe. (Note: in the public transport push for more multi-modal options for users, Optibus also incorporates data about public bike, scooter and taxi access points but doesn't provide data about their movements -- not now, at least.)

Optibus's rise underscores to a critical moment for the world of public transportation.

Mass transit services like buses and subways took a huge hit in the last couple of years, with numbers of users declining by some 80% globally in the wake of Covid-19: people stayed home more to work; when they did go out, they generally wanted to avoid contact with others and crowds so stayed off public transport; and public transport organizations themselves also reduced services and passenger flow to fit with public health rules.