Even though the company offers nothing but cryptic clues when talking about its existence, Apple’s long-rumored electric car is almost certainly in development. Now, the Cupertino firm has been granted its first vehicle patent, but it’s not what people were expecting.

The US Patent and Trademark Office granted 80 new patents for Apple yesterday, one of which shows designs for what resembles an articulated bus or truck sporting tank tracks instead of wheels.

This particular patent is actually for the linking mechanism that connects the two cabins. It’s said to help a driver control both parts of the vehicle and improve reliability in cold weather conditions by feeding warm air through the link, thereby reducing the risk of snow and ice damage.

Don’t expect the Apple car to ship with tank treads and be an awesome off-roader. Patently Apple reports that Swedish military vehicle manufacturer BAE Systems is listed as the assignee of the patent, so it’s almost certainly not going to end up as part of a commercial vehicle.

Earlier this year, Tesla CEO Elon Musk said Apple’s car, codenamed Project Titan, was an open secret. He highlighted the huge number of people Apple had hired from the automotive industry over the previous 12 months as evidence. "Well, it's pretty hard to hide something if you hire over a thousand engineers to do it," he said.

A former Apple employee who claims to have worked on the Project Titan team says the car will now launch in 2021, rather than the planned date of 2020. Additionally, senior Apple executive Bob Mansfield, the man who led the engineering development of the iPad, MacBook Air and iMac, was brought back to head up the Apple car project, as the company shifts its focus toward self-driving software.

It may not be associated with Project Titan, but at least the new patent shows Apple continuing to develop vehicle-related technology.