Toyota, the world’s largest automaker, will once again unveil the latest iteration of its self-driving test vehicle at CES in Las Vegas next week. The TRI-P4 test car is designed by the Toyota Research Institute, the automaker’s Silicon Valley-based division, and the major upgrade over the third version of the vehicle is — wait for it — more trunk space.

On the surface, that might not sound very impressive, but those with more than a passing familiarity with autonomous vehicle design will recognize it as a major step. Most Level-4 capable self-driving cars on the road today — meaning those cars that can perform all the driving tasks within a confined area and under specifics conditions — have high-powered computers in their trunks. These computers run the deep learning algorithms used by the vehicle’s perception software to “see” and identify the world around it, as well as capture and record every moment while the car’s in motion. The computers get hot while they work, requiring water-cooling with hoses and radiators, which eat up even more space.

Toyota’s big innovation was to shrink down all this equipment and free up an enormous about of space in the trunk, which should make these vehicles more appealing to potential customers or service operators. After all, who would want to get picked up at the grocery store in a self-driving taxi with no space in the trunk for your bags? According to TRI, the compute box “has been reimagined” and is now tucked vertically against the rear seat transom, folding down to access the circuitry.

The TRI-P4 can see better, thanks to two additional cameras in the sensor suite, and is “smarter” compared to previous versions, the institute claims. The radar system has a better field of view, especially for close-range detection around the vehicle perimeter.

And with greater computing power, the vehicle’s systems can operate “more machine learning algorithms in parallel for faster learning. It can process sensor inputs faster and react more quickly to the surrounding environment,” TRI says. The reimagined compute box is now drawn from the vehicle’s hybrid battery, with the 12V battery now serving only as a backup. And to cap it all off, Toyota upgraded to a newer model Lexus LS for its fourth-generation test vehicle.

The design of the vehicle is very similar to the third generation, swapping a white paint job for a gray one. Toyota says it expects to begin testing the new vehicle in the spring.

The automaker is pursuing two autonomous vehicle products in parallel: Chauffeur and Guardian. “Our Chauffeur development is focused on full autonomy, where the human is essentially removed from the driving equation, either completely in all environments, or within a restricted driving domain,” said Ryan Eustice, senior vice president of automated driving at TRI, in a statement. “Guardian, on the other hand, is being designed to amplify human performance behind the wheel, not replace it. The introduction of the new P4 platform will help us accelerate the development of both tracks when it joins our fleet this spring.”

Toyota recently agreed to invest $500 million in a joint self-driving project with Uber. As part of the agreement, the two companies will work together on developing self-driving cars. Uber recently restarted its self-driving program after one of its vehicles killed a pedestrian in Arizona last March.