Robotaxi pioneer Waymo has raised another $16 billion to help fuel its ambition for its fleet of self-driving cars to provide rides throughout the world while other deep-pocketed rival services backed by Tesla and Amazon try to catch up.

The fundraising announced Monday values Waymo at $126 billion.

The appraisal underscores investors’ desire to own a piece of the rapidly expanding robotaxi market, as well as how far Waymo has come since starting as a “moonshot” project within Google 17 years ago. Analysts had estimated Waymo was worth about $30 billion just five years ago after a flurry of fundraising.

The new valuation may feed recurring speculation that Waymo will eventually pursue an initial public offering as part of a spinoff from corporate parent Alphabet Inc, which also owns Google.

Alphabet, which boasts a market value of nearly $4.2 trillion, led the fundraising that also included an array of prominent venture capitalists and investment funds.