The current-generation Toyota Prius hybrid is due for replacement soon, but Toyota has been tight-lipped when it comes to details about that new model.

Carmakers go to extraordinary lengths to keep their upcoming models secret, and to ensure that whatever or auto show or other venue chosen for an unveiling really is the first time these cars are seen by the public.

Sometimes, though, things just slip out.

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New models must undergo testing on public roads, and in this age of omnipresent personal cameras, that creates plenty of opportunities for exposure.

Video of a heavily-camouflaged vehicle stopped at a gas station was recently posted on the Prius Chat forum, and the poster believes it could be the fourth-generation Prius.

With all of its black coverings, the car certainly looks like a prototype vehicle.

Possible fourth-generation Toyota Prius prototype. Video by Vimeo user Savior1974.

Possible fourth-generation Toyota Prius prototype. Video by Vimeo user Savior1974.

It also appears to have a similar hatchback shape to the Prius.

Also worth noting are the bumps on the panel ahead of the door mirrors, which one commenter claims are vortex generators.

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Other features are harder to discern, but the car does seem to have fairly aggressively-shaped headlights and taillights.

That would line up with what we've heard about the next-generation Prius so far.

Possible fourth-generation Toyota Prius prototype. Video by Vimeo user Savior1974.

Possible fourth-generation Toyota Prius prototype. Video by Vimeo user Savior1974.

The new model is expected to emphasize style a bit more, as Toyota attempts to broaden its appeal.

A previous report claimed the original design for the next Prius was rejected for being too staid, and that designers were forced to start over.

MORE: Toyota Prius Plug-In Production To End In June; New One Coming Next Year

The Toyota C-HR concept--a compact crossover that debuted at the 2014 Paris Motor Show--has been discussed as a possible influence for the final design.

It's also likely that the Prius will adopt styling cues from other recent Toyota models, such as the refreshed 2015 Camry.

Possible fourth-generation Toyota Prius prototype. Video by Vimeo user Savior1974.

Possible fourth-generation Toyota Prius prototype. Video by Vimeo user Savior1974.

A new version of the Prius Plug-In Hybrid is on the way as well--although it may feature different styling from the standard model.

Flashier styling will help the Prius stand out in a green-car field that's much more diverse than when any of the previous generations launched.

In addition to a wider range of hybrids, the Prius now faces competition from battery-electric and plug-in hybrid models.

But we don't expect to see the final shape until the 2015 Tokyo Motor Show this fall, at the earliest.

That means the Prius could launch in the U.S. either as a 2016 or 2017 model.

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