The Toyota Prius will be celebrating its 10th anniversary later this year. The iconic hybrid car is going stronger than ever—with nearly 750,000 units on roads throughout the world and the pace of sales continuing to rise. Looking back to the birth of the Prius, the engineers behind the vehicle were apprehensive about being able to achieve their goals.

In 1994, Akihiro Wada, then executive vice president of Toyota, set a challenge before the project’s engineers: to double the fuel efficiency compared with a conventional vehicle. That was difficult enough. On top of that, Toyota’s president at the time, Hiroshi Okuda, told the group to complete its work years ahead of schedule, in order to introduce the vehicle in 1997, the year the Kyoto Protocol was adopted at the U.N. conference on climate change.

Prius Engineers

The engineering team for the first-generation Prius.

The response from Takeshi Uchiyamada, chief engineer of the first-generation Prius, was, “That’s impossible.” But the executives stuck to the 1997 deadline. According to the legend, Uchiyamada was given the option of completing the assignment or quitting his job. He sought inspiration by reading stories about people who had accomplished impossible goals. The team made hybrid history by releasing the Prius as the world’s first gas-electric car in December 1997.

An Entire Line of Impossible Cars

Ten years later, the Prius is considered a smash hit—the right car for a world under the spell of a sustained energy and environmental crisis. With the Prius due for a redesign in 2008 (as a 2009 model), Toyota is now considering where to take its hybrid vision. We saw hints of Toyota’s plans for the next-generation Prius at the 2007 Geneva Auto Show, in the form of the Toyota Hybrid X concept design. Now, new rumors (and images) of design concepts are circulating the Internet.

Toyota may go even further by establishing “Prius” as a separate brand. Last year, Jim Lentz, executive vice president of Toyota U.S. sales, dropped hints of a smaller “city car” based on the Prius, as well as a potential small SUV version. “People also want to see more utility on the vehicle, so you could imagine something that’s a little more utility or crossover-based,” said Lentz, who was speaking at Specialty Equipment Market Association trade show in Las Vegas in Nov. 2006.

Now, according to Automobile.com, planning for a three-vehicle Prius lineup is apparently underway. The article states:

The Prius brand name would feature a three car lineup with vehicles called A, B and C. Prius A would be launched in 2009 (coinciding with the estimated launch date of the new Prius), Prius B in 2010, and finally Prius C in 2011. Once the launch of the Prius brand occurs, it is rumored that Toyota will cease to sell hybrid vehicles under its own product name.

These are just rumors, but they reveal the challenges Toyota faces in duplicating the Prius halo, and setting it upon an entire lineup of vehicles. That might prove to be an impossible goal—even less achievable than the original creation of the Prius 10 years ago.