It’s likely to be several years before you can buy a self-driving car. But a crop of startups is already selling self-driving shuttle buses that are being used in university campuses and corporate parks and could also work at airports, factories and theme parks.

These companies, such as Navya and Local Motors, together have raised more than $100 million from investors that include GE, Airbus and Y Combinator. What makes them worth watching is that they have a head start on technology that could eventually hit the consumer market. Unlike bigger firms developing self-driving systems, like Google, Ford and Tesla, these small companies are getting real-world commercial experience selling and operating self-driving vehicles. Because they largely sell to customers that own private roads, they’re able to avoid government regulation that’s slowing down big tech companies.