Toyota Motor Corp. says it is the first auto maker to have a plug-in hybrid-electric vehicle (PHEV) certified for use on public roads in Japan, with recent approval by the Ministry of Land, Infrastructure and Transport.

PHEVs have an external charger that can be plugged into a home outlet overnight, providing enough power for short-range urban driving as an electric vehicle.

During lengthier trips, a PHEV operates as a typical hybrid-electric vehicle, making use of a gasoline engine and electric motors, enabling them to run in a wider range of driving conditions solely on battery power.

Toyota says it will provide the Japanese government with data for formulating testing methods for emissions and fuel efficiency – measures it would like to see used for promoting PHEVs and the use of electricity.

The auto maker’s Toyota Motor Sales U.S.A. Inc. (TMS) subsidiary also is providing eight PHEVs to the Advanced Power and Energy Program at the University of California, Irvine, and the Institute of Transportation Studies at the University of California, Berkeley, as part of an ongoing sustainable mobility development program it shares with the two campuses.

The next phase of its U.S. evaluation program, the auto maker says, will be conducted in partnership with the Alternative Fuel Incentive Program jointly developed by the California Air Resources Board and the California Energy Commission.

The overall goal of the program, which has been authorized by the State of California, is to evaluate various advanced vehicle transportation systems and urban designs, including the production of alternative fuels and vehicles, says Dave Illingworth, senor vice president and chief planning officer for TMS.

“The Toyota Prius convinced mainstream consumers of the merits of hybrids,” he says in a statement. “Although there is much work to be done with plug-ins, we see this pilot program as a significant step in the advancement of the technology.”

Masatami Takimoto, Toyota executive vice president-powertrain development and quality, told reporters at the Geneva auto show in March that the auto maker was “accelerating development” to introduce a PHEV as soon as possible.

Detroit’s Big Three auto makers, as well as U.S. battery suppliers and energy companies, also are working with plug-in technology.

Ford Motor Co. in July said it was partnering with Southern California Edison to test a fleet of PHEVs. The utility, which provides service to 13 million people in 11 Southern California counties outside Los Angeles, will receive one Ford Escape PHEV by the end of this year and up to 20 by 2009.

DaimlerChrysler AG plans to have up to 20 ’07 Dodge Sprinter van PHEVs on the road between now and first-quarter 2008, as part of its fleet-test programs.

General Motors Corp. shook up the industry when it introduced the Chevrolet Volt concept PHEV at the North American International Auto Show in January, which the auto maker says is capable of 150 mpg (1.56 L/100 km).

The Volt is designed to run solely on charged electric power for a range of 40 miles (64 km). When that power supply starts to wane, a 1.0L, 3-cyl. turbocharged engine, burning gasoline or alternative fuels, kicks in to generate power to run the electric motor.

Unlike traditional HEVs, the Volt is a series electric hybrid because the internal combustion engine does not provide propulsion. The car also is designed to store energy via a lithium-ion battery pack – supplier technology that is still very much in the development stage. When the entire powertrain is considered, the Volt has a 640-mile (1,029 km) range.

GM managers have said they want to leverage the auto maker’s global manufacturing capability to manufacture the Volt in several different regions, rather than produce a low-volume niche model solely for the U.S.

Toyota’s PHEV prototypes, which share the same gasoline-powered internal combustion engine and electric motor hybrid system used in the Prius, have a top speed of 62 mph (100 km/h).

However, Toyota says increased battery capacity gives the vehicles a longer electric motor-only cruising range, and a battery-charging device allows users to replenish the batteries using household electricity.

Thanks to these features, the 5-passenger PHEVs can run more often in gasoline-free, electric-only mode, such as on short trips in city driving, the auto maker says.

“The resulting fuel-efficiency improvements mean lower CO2 (carbon dioxide) emissions and less fossil-fuel consumption and, therefore, less pollution,” Toyota says in a statement.

“Also, charging the battery with less-expensive night-time electricity lowers total running costs, providing an economic benefit to owners.”

Although challenges still exist in the development of pure electric vehicles, such as a limited cruising range and issues related to cost, Toyota says it continues to view PHEVs as a promising environmentally friendly technology and that it is committed to their continued development.

The Toyota PHEV being tested is 131 ins. (333 cm) long, 69 ins. (175 cm) wide, 59.6 ins. (151 cm) high and weighs 2,998 lbs (1,360 kg).

Its 1.5L gasoline engine has a maximum output of 75 hp at 5,000 rpm, while the electric motor’s maximum output is 67 hp (59 kW) at 1,200-1,540 rpm.

Maximum torque is 369 lb.-ft. (500 Nm) at 1,200 rpm using the combined engine and electric-motor power.

The PHEV’s secondary battery is nickel-metal-hydride and recharges using household current. Toyota says that takes 60 to 90 minutes at 200 volts and three to four hours at 100 volts. The overall system has a maximum output of 134 hp (100 kW) and voltage of 202-500V.

Most auto makers and suppliers involved in PHEV technology today agree that battery development is the real stumbling block.

Rechargeable Li-ion batteries, much like those used in many of today’s consumer-electronic devices, will produce new possibilities for performance, they say, but their production is several years off.

The industry also is anxious to speed Li-ion development because the price of nickel (used in current NiMH batteries) has tripled in the last five years.

Toyota estimates that over the past decade, hybrid vehicles worldwide have emitted approximately 3.5 million fewer tons (3.2 million t) of carbon dioxide than gas-powered vehicles of the same class.