Efficiency is growing slowly, but Weight of the car, miles traveled and quantity of cars on the road all increasing much more rapidly so there is an increasingly negative effect on the environment.
There have been developments in economically friendly cars, but none have been much of a success.
The development of the hyper car (www.hypercar.com), with ultra light construction (mainly carbon and glass fiber rather than aluminum and steel resulting in it being about a third of the weight of an average car), a hybrid electric engine and numerous energy saving devices.
But past experiences such as the Renault Vesta, which can run 100 mpg, have shown it is not perhaps technology which is lacking but unfortunate consumer behavior i.e. the lack of demand for low performance but energy efficient cars. With powerful, bigger and safer cars with gadgets (such as a/c etc) being a much higher consumer preferences than efficiency .shown by a lack of fuel efficiency increase over the last ten years, especially in America (http://www.eia.doe.gov/emeu/25opec/sld011.htm)
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