Citroen Cactus 001
The Citroen Cactus concept hatchback made its debut at the 65th International Motor Show in Frankfurt, that runs through Sept. 22. Doors open to the public on Saturday. The Cactus is the second Cirtroen to debut at a car show that features PSA Peugeot Citroen's Air Hybrid technology. Instead of an electric motor, this hybrid uses compressed nitrogen gas and a hydraulic pumping system as the secondary power source. PSA Peugeot Citroen

The PSA Peugeot Citroen (EPA:UG) rolled into the 65th International Motor Show in Frankfurt with two interesting innovations, one it had previously unveiled in March in Geneva and the other now making its debut in Frankfurt.

The Citroen Cactus Concept hatchback has some bold features – outside and beneath the floorboard – as well as a distinctly French interior design. Whether a production version of the Cactus will ever make it to showrooms is unclear, but it does offer hints at the direction PSA is taking for Citroen’s C line of compacts.

The most obvious of these features is the so-called Airbumps, the rubbery surface that covers parts of the car’s panels and corners — the hot spots for dings and dents. Think of it as a car’s version of the rubbery cases used to protect smartphones and you get the idea. The texture and blue trim is cosmetic and could change, but PSA says it is taking the concept of integrating protective surfaces seriously. This type of car is often used in the urban environment, so a feature that protects it from stray shopping carts and careless parkers might actually work.

The Cactus also replaces the shifting knob with buttons and puts most dashboard controls in a 7-inch touchscreen. It’s a French car (and a Citroen at that), which means a lot of attention has been paid to the interior design.

The Cactus is the second PSA vehicle car to appear at a car show with the Hybrid Air system that PSA says will give vehicles like this up to 94 miles per gallon, and even more than 80 in stop-and-go urban traffic, with one of the lowest emission levels of any gas-burning car on the market.

The system uses a tank of compressed nitrogen gas and a separate tank of hydraulic fluid that can be injected like a syringe into a hydraulic motor, giving the car a range of a few hundred yards without using gasoline. The system can power or partially power the car as it accelerates or crawls slowly in heavy traffic. Pressure is returned to the tank the same way conventional hybrids harvest energy from braking; in the case of the Hybrid Air system a reversible hydraulic pump sends pressure back into the tank.

The idea is simple: save gas in tiny increments that add up over time. The technology isn’t new – it’s been used in stop-and-start vehicles like garbage trucks to power the trash compactors; what is new is using this system in a hybrid passenger car.