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Robotaxi pioneer Waymo has raised another $16 billion to help boost its ambition for its fleet of self-driving cars to provide rides around the world as other competing services backed by Tesla and Amazon try to catch up.

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The fundraising announced Monday values ​​Waymo at $126 billion.

Read more: Waymo’s automated vehicles begin transporting passengers in Atlanta, expanding Uber’s partnership

This valuation underscores investors’ desire to own a piece of the rapidly expanding robotaxi market, as well as how far Waymo has come since it began as a “Moonshot” project within Google 17 years ago. Analysts estimated Waymo was worth about $30 billion just five years ago after a wave of fundraising.

The new valuation may fuel recurring speculation that Waymo will eventually seek an initial public offering as part of a spin-off from parent company Alphabet Inc, which also owns Google.

Alphabet, which has a market capitalization of nearly $4.2 trillion, led the fundraising that also included a group of prominent venture capitalists and investment funds.

Read more: Tesla is losing its title as the world’s largest electric car maker after sales declined for the second year in a row

In a blog post, Waymo said it plans to use the funds to expand its reach beyond the six metropolitan areas where its robotaxis already make trips in California, Arizona, Georgia, Texas and Florida. It is preparing to enter more than 20 other cities, including London and Tokyo. Waymo’s robot car already provides more than 400,000 rides per week.

“We are positioned to move forward at unprecedented speed, while maintaining our industry-leading safety standards,” Waymo said in the post.

Although Waymo’s robotaxis have so far compiled a mostly clean driving record, they have encountered several issues that have sparked community backlash and regulatory inquiries.

Read more: The US is opening an investigation into Tesla after more incidents involving its so-called full self-driving technology

Last year in San Francisco, a Waymo robotaxi ran over and killed a 9-year-old cat that was beloved in her neighborhood. Several self-driving vehicles later contributed to traffic chaos during a prolonged power outage when they stopped at intersections with dark traffic lights. The National Transportation Safety Board is also investigating complaints in Austin, Texas, about Waymo robotaxis operating unsafely around school buses carrying children.

Waymo is bracing for more competition from Amazon-backed Zoox in San Francisco and Tesla, as it continues to follow through on CEO Elon Musk’s promise to build a network of robots across the United States.