Waymo has a new partner. The Alphabet (GOOG -1.30%) (GOOGL -1.21%) self-driving subsidiary has inked a deal with Daimler's (MBGY.Y -0.35%) heavy-truck unit, in which the two will work to create self-driving tractor-trailers based on Daimler's Freightliner Cascadia trucks and the Waymo Driver autonomous taxi system.

Daimler Trucks and Buses is one of the world's largest heavy-truck and bus manufacturers. The unit, which has been working to develop self-driving trucks for several years, acquired autonomous-vehicle software maker Torc Robotics last year, integrating Torc's expertise into its broader effort to develop self-driving trucks. 

That effort will continue in parallel with the new Waymo partnership, Daimler Trucks' chairman Martin Daum said. 

A Freightliner Cascadia, shown pulling a trailer on a mountain highway.

Daimler Trucks and Waymo will work to develop a self-driving version of the Freightliner Cascadia heavy truck. Image source: Daimler AG.

"This partnership complements Daimler Trucks' dual strategy approach, of working with two strong partners to deliver autonomous [Level 4] solutions that are seamlessly integrated with our best-in-class trucks, to our customers," said Daum.

Level 4 autonomous systems are those that can safely drive a vehicle without a human, but only under limited conditions. Generally, they are "geofenced," meaning limited to areas that have been carefully mapped, and they may also be restricted from operating during certain types of severe weather. 

In an interview with Automotive News, Daum said that Daimler's work with Waymo will begin with a focus on developing trucks that can be more easily integrated with self-driving systems. Because there's no human to intervene in an emergency, self-driving vehicles require redundant steering and braking systems to keep them operating safely in the event of a component failure. Such systems don't yet exist for heavy trucks.

The companies did not announce a timetable for the development and deployment of self-driving tractor-trailers.