Waymo is one of the frontrunners of robtoaxi race, offering the public more than 100,000 rides, according to the company.Jason Henry/AFP via Getty ImagesGM has bowed out of the robotaxi race for now, halting its investment in Cruise.Only a few companies have made significant strides in the autonomous taxi space.Tesla and Waymo are the two frontrunners due to the progress they've made with self-driving.General Motors' white flag in the robotaxi race on Tuesday just made the autonomous ride-sharing competition much smaller in the US, showing how challenging it can be for companies, even with the capital, to compete if they haven't already made significant headway in autonomy.Eight years and more than $10 billion in investment later, GM said that the resource-intensive nature of Cruise and an increasingly competitive market has pushed the company to shift away from its robotaxi dreams.