A worker prepared a Citroen C-Cactus prototype car at the 62nd International Motor Show last year in Frankfurt, Germany.

PARIS -- As governments seek to cut carbon emissions through regulation and consumers react to rising fuel prices, automakers and designers are mapping out a new generation of lighter, sleeker vehicles that could give a radical new look to urban streets.

Toyota has already set a benchmark for low emissions and fuel economy. Its Prius model, introduced in 1997, pioneered new technologies, including the first fully integrated hybrid engine, able to switch between gasoline and battery power, and electronic and computerized controls replacing heavy hydraulic systems.

Toyota has been followed by another Japanese company, Honda, with a Civic hybrid, and a string of releases or planned models from European and American competitors. Carmakers are now racing to design more innovative bodies incorporating advanced aerodynamics and light, biodegradable plastic components. They are also trying to second-guess the kind of styling that the next generation of car buyers will want.

Gilles Vidal, designer of a recent "green" concept car, the C-Cactus, for the French automaker PSA Peugeot Citroën, said, "To make a real environmental effort, you need to work on all of the possible factors -- materials, optimization of processes, simplifying, going back to essentials."