Hybrid electric vehicles (HEVs) are a valuable means to reduce petroleum consumption. These vehicles combine a conventional internal combustion engine with an electric motor. The result is a vehicle with low emissions and high fuel efficiency. The vehicles do not need to be plugged-in to recharge the batteries, as the batteries are charged via an on-board generator and regenerative braking system. As a result, the vehicle retains the range, performance and convenient fueling of conventional vehicles. 

King County Metro Transit unveiled its diesel hybrid electric buses in May of 2004. Over 200 hybrid buses are now being introduced into the fleet.

Not all HEVs are created equal - the fuel economy, emissions benefits and performance vary depending on the size of the vehicle and the technology employed. In some cases, the electric motor is generally the primary source of power at low speeds, with the engine providing power during heavy acceleration, high speeds and to operate the generator for battery recharge. In other cases, the electric motor is used only while the vehicle is idling. 

The use of the electric motor allows hybrid electric vehicles to significantly reduce emissions compared to traditional gasoline vehicles. Emissions reductions are dependent on the fuel efficiency and cleanliness of the gasoline engine and the amount of power provided by the electric components. In some light-duty vehicles, exhaust emission of hydrocarbons, nitrogen oxides and carbon monoxide are reduced over 50 percent, and have been shown to be reduced as much as 90 percent. Compare hybrid vehicles.

As with electric vehicles, the primary safety concerns relate to the handling of vehicle batteries and electrical connections, as there is the potential for electric shock, as well as contamination and chemical burns from batteries. The disposal of batteries can pose contamination concerns, however, the batteries in hybrid vehicles are expected to be longer-lived than those in purely electric vehicles.

The majority of available models use traditional gasoline and diesel engines, with some heavy-duty hybrids using alternative fuels, such as natural gas, in combination with the electric motor. It is hoped that additional alternative fuel options will be developed in the future. Available light-duty hybrid vehicles include sedans, SUVs and trucks. The Toyota Prius, Honda Insight and Honda Civic were the first hybrids to be sold in the US. The Ford Escape, Lexus RX450h, Toyota Camry and Mercury Mariner are now among the many options available.

Hybrid technology has spread beyond light-duty vehicles. Medium-duty hybrid trucks are available in a variety of styles and configurations and more and more applications are being tested every day. Hybrid technology in this sector may take the form of either electric or hydraulic hybrids. In addition, heavy-duty hybrid electric buses are also available, such as the hybrid-electric diesel buses operated by King County's Metro transit service. WestStart-CALSTART created the Hybrid Truck Users Forum (HTUF) that has taken a leadership role in bringing medium- and heavy-duty hybrid trucks to market.

The US Department of Energy provides additional information on available of light- and heavy-duty hybrid vehicles. DOE also provides a cost calculator tool to determine if an HEV makes sense for your fleet. There is a federal tax incentive for hybrid electric vehicles. If you are considering an HEV for your fleet, keep in mind that hybrids do not meet the alternative fuel vehicle mandate requirements of the Energy Policy Act (EPAct).

Plug-in Hybrid Electric Vehicles (PHEVs): In brief, plug-in hybrid electric vehicles (PHEVs) extend the electric capabilities of an HEV so that it can travel some distance solely using battery power. The vehicles have larger battery packs than current HEVs and the batteries can be plugged into a standard outlet for recharging. When the batteries are sufficiently depleted, the vehicle relies on the internal combustion engine and most operate just like a regular HEV at that point.

To date, PHEVs have not been commercially produced by original equipment manufacturers (OEMs) but conversions of HEVs have been completed by other groups (See CalCars). In particular, A123/Hymotion offers a conversion kit that has been crash tested. There is a certified installer of this kit in the Seattle area. (For more information on this option, visit the company's website.)

PHEVs are often described in terms of the range on which they can travel solely on electric power - common ranges are 20-40 miles. Depending on driving patterns, these vehicles would have substantial improvements in fuel economy over conventional or even hybrid vehicles.

National Clean Cities Program strategies:
Clean Cities supports the use of hybrid vehicles through a combination of strategies:

• Exploring opportunities to educate consumers and fleets about the benefits of hybrid technologies.
• Tracking product availability and growth potential.
• Developing information concerning hybrid life cycle costs and benefits, funding sources, federal and state incentives, and case studies.

The National Clean Cities Program also plans to focus on demonstration projects for medium- and heavy-duty hybrid vehicles and will assess whether to play a role in promoting the hybrid resale market or in developing new markets, such as hybrid leasing and rental cars.

Puget Sound Clean Cities Coalition strategies:

The following strategies will guide the work of the Puget Sound Clean Cities Coalition in this area:

• Provide education via website, at workshops and at vehicle displays.

• Include hybrid electric vehicles in state and local legislative efforts as appropriate.

• Support the initial pilot projects on PHEVs however possible and share the results with other fleets in the area.

Additional Resources

• The US Department of Energy provides additional information about hybrid electric vehicles and plug-in hybrid vehicles. Information includes vehicle availability, benefits, maintenance, safety and the future of hybrid technology as well as links to additional resources.

• HybridCenter.org, which is a project of the Union of Concerned Scientists, has a lot of information on HEVs including a Buyer's Guide.

• HybridCars.com is another website with a wealth of information about HEVs. This site has a calculator that provides information on the fuel, emissions and cost savings possible with an HEV compared to a conventional vehicle.

• Plug-in Partners and CalCars are two of the main groups promoting PHEVs and have much information on their websites.

• Electric Drive Transportation Association (EDTA) is the industry association working to advance electric vehicle transportation technologies and supporting infrastructure through policy, information and market development initiatives. The website includes detailed information on existing and future electric vehicle technologies.

• WestStart-CALSTART created the Hybrid Truck Users Forum (HTUF) that has taken a leadership role in bringing medium- and heavy-duty hybrid trucks to market. The website has a wealth of information on a variety of hybrid trucks.