TOKYO – Four of Japan’s leading auto makers this summer publish sustainability reports that provide a collective roadmap for where the domestic industry is headed in the environmental and safety fields.

Toyota, Nissan, Honda and Mazda all say they are building on existing technology and developing new hardware to make their vehicles greener and safer in both the short and long terms.

Toyota this month says 95.1% of all models in its lineup in fiscal 2010 met super-ultra-low-emissions vehicle (SULEV) standards. The auto maker, which early this year launched the Prius Plug-In Hybrid in the U.S. and Japan, reported in May it had sold 4 million hybrids globally since the 1997 launch of the original Prius.

In the domestic market, Toyota reports nearly 60% average fuel-economy improvement, including hybrids, between fiscal 1997 and fiscal 2010, while the average in the U.S. and Europe rose 34% in the same period.

In the report’s European edition, the auto maker says it has achieved a fleet average of 126.5 g/km of carbon-dioxide emissions, ahead of the European Union’s 128.2 g/km target. The Yaris Hybrid, launched in May, leads its class with 79 g/km and city fuel economy of 76 mpg (3.1 L/100 km).

Toyota predicts it will achieve future EU emissions target of 120 g/km in fiscal 2015 and 95 g/km in fiscal 2020.

Toyota Europe reports sales of 400,000 hybrids through March, one-tenth of the auto maker’s global total since the Prius launched.

Nissan says it plans to offer four electric vehicles in global markets by 2014. At the top of the list is the Leaf electric car, now being sold and tested in more than 30 countries, as well as EV versions of a light-commercial vehicle and Infiniti luxury car.

Fleet tests of the eNV200 minivan, unveiled in January at the North American International Auto Show in Detroit, are under way in Japan and the U.K.

Leaf and lithium-ion battery production at Nissan North America begin later this year and at Nissan Motor Mfg. U.K. in 2013. Planned capacity at the auto maker’s Smyrna, TN, plant is 150,000 Leafs and 200,000 battery packs, and 50,000 Leafs and 60,000 battery packs at the Sunderland, U.K., facility.

The auto maker estimates CO2 emissions over the Leaf’s lifetime will be 40% less than a comparably sized gasoline car.

Nissan will launch a new a new Altima model hybrid model in 2013 in North America, supplier sources indicate.

In the safety field, Nissan says it achieved its 2015 target for reducing fatalities and serious injuries in 2009, six years ahead of schedule. That target was 50% of 1995 levels. The auto maker now aims to cut the total by half again by 2020 in the U.S., Japan and the U.K.

To achieve its 2020 target, Nissan steadily has been introducing advanced safety technologies, starting in 2009 with distance control-assist on the Fuga and Infiniti M series luxury sedans and lane-departure prevention on the Skyline and Infiniti EX, FX, JX, M and QX models.

In 2010, it added blind-spot intervention on the Infiniti M series and, in March of this year, backup-collision intervention on the JX series. The Fuga and Skyline are the Japanese versions of the Infiniti M and EX series.

With the launch of the new Altima in June, Nissan added blindspot, lane-departure and moving-object warning capability to its “around-view” monitoring system, which debuted with the 2007 launch of the Elgrand minivan in Japan and Lexus EX35 luxury cross/utility vehicle in North America.

The auto maker added navigation systems in 2009 with the Skyline launch.

Honda, which began overhauling its powertrain lineup in December 2011, intends to cut CO2 emissions 30% by 2020 compared with 2000 levels. To reach the target, the auto maker will introduce six new engines – five gasoline and one diesel – and three continuously variable transmissions over the next three years.

The gas engines, most of which will feature direct injection and stop/start technology, include 1.3L-1.5L, 1.8L-2.0L, 2.4L and 3.5L units. The 3.5L powerplant is a V-6. Honda’s common-rail diesel, to be installed in the new U.K.-built Civic, has a displacement of 1.6L.

Addressing safety, Honda introduced a blindspot information system on the ’10 Acura ZDX and MDX models, followed by the Acura TL and Honda Odyssey Touring Elite in 2011. The MDX, ZDX and RL are equipped with collision-mitigation braking, as are most Honda models sold in Japan; they include the CR-V, Civic, Elysion, Inspire and Stream.

With the launch of the new Accord, Honda will introduce “Lane Watch,” which packages blindpot, lane-departure and front-collision warnings into a single system.

Other advanced safety technologies offered by Honda are night vision on the Legend and lane-keeping assist on the Accord, Legend and Odyssey in Japan and Acura RL in the U.S.

Mazda, although trailing Japan’s Big Three in introducing advanced safety technologies, offers blindspot and rear-vehicle monitoring, dynamic stability control and adaptive front lighting.

In the powertrain area, Mazda in August reiterated it would build upon its Skyactiv engine and transmission technologies that debuted in June 2011. Over the next few years, the auto maker will add start/stop, regenerative brakes and hybrid technologies.

Through this building-block approach, Mazda says, it is committed to improving fuel economy 30% throughout its lineup in 2015, when it plans to incorporate Skyactiv engines and transmissions in 80% of Mazda cars sold globally.

The auto maker says 98.5% of its vehicles sold in Japan as of March 31, 2011, meet SULEV standards and that the Mazda3, Mazda6 and CX7 are Euro 5-certified.

Mazda confirms it will introduce an EV based on the Demio subcompact this year, followed by a hybrid car in 2013.

The exploding numbers of vehicles on the world’s roads are driving much of the research into low-CO2-emissions engines. Nissan’s report cites a United Nations forecast that global population will grow from 7 billion at present to 9 billion in 2050, with 70% living in cities.

“To keep average temperatures from rising more than 35.6° F (2° C), atmospheric CO2 needs to be stabilized at 450 parts per million," the report concludes. Based on that assumption, we have calculated that ‘well-to-wheel’ CO2 emissions for new vehicles must be reduced by 90% in 2050 compared to 2000 levels.”

The International Energy Agency estimates that to cut CO2 emissions in half by 2050, 1 billion out of a projected 2 billion vehicles in operation worldwide will have to be plug-in hybrids, EVs or fuel-cell vehicles.