Alphabet’s Waymo still hasn’t perfected a self-driving car. So it is throwing more money at the problem.

Waymo nearly doubled its headcount to 1,500 employees, known as “Waymonauts,” from 800 about a year ago, said a person with knowledge of the figure. Much of the expansion came from the hiring of hundreds of engineers Waymo hopes will help it achieve a technological breakthrough in developing a reliable self-driving vehicle.

The workforce expansion suggests Waymo’s annual cost is nearing $1 billion, while its brand-new automated taxi business is yielding just hundreds of thousand dollars a year in revenue. One signal that Waymo is a long way from developing into a business was the departure last fall of Waymo’s first chief commercial officer, Amee Chande, after just 10 months on the job. Her departure hasn’t previously been reported.