Maybe it's the threat of a rejuvenated rail system or prepping for a carbon cap law, but transportation companies are accelerating efforts to push diesel-electric trucks into commercial markets. Soon delivery vehicles and 18-wheelers will be softer on the environment while saving money.

While emissions regulations enacted during the past few years have reduced the environmental impact of diesel trucks (and fuel), adding hybrid technology can further lower their carbon footprint while protecting companies against rising fuel prices.

This week's National Truck Equipment Association (NTEA) Work Truck Show included the debut of two diesel-electric vehicles, including an innovative hydraulic hybrid van from Freightliner. Freightliner Custom Chassis Corporation (FCCC)'s walk-in van improves fuel efficiency by up to 70 percent, according to the company.

The company is more efficient in recovering braking energy (and reducing wear and tear on the brakes) by storing the energy in a hydraulic accumulator, which puts pressure on a fluid that is released to create energy.

Accumulators experience less energy loss than the process of transferring regenerative braking energy back and forth with batteries. Freightliner says the hydraulic system requires less space than using batteries as it is ten times more energy dense.

Freightliner's full hybrid system enables the engine to be shut off when stopped. Previously the company had delivered prototypes to UPS and FedEx.

Also at the show is the Navistar DuraStar Hybrid truck that is being used by Kraft Foods. The truck uses energy captured from the brakes to keep food products chilled in the refrigerated body.

The mild hybrid design will save 30 percent in fuel over typical diesel trucks, according to Navistar.

Also, American Honda announced this week it will be delivering parts using a Peterbilt diesel hybrid truck. The company will compare how the Class 8 truck performs compared to a conventional diesel truck during a year-long trial.

On the international scene, Mitsubishi has sold 500 diesel hybrid trucks in Japan and has 10 of its Canter Eco Hybrid trucks being tested in England.

The federal stimulus package included billions for local and high-speed rail, emphasizing the railroads' ability to move people (and goods) at lower monetary and environmental cost. According to data from the Oak Ridge National Laboratory cited in the book "Profit From The Peak," freight moved by rail requires just 11 percent of the energy of moving goods by heavy truck. Moving to diesel hybrid technology will close some of that wide gap.

Transportation companies would be directly impacted by the passing of carbon cap and trade legislation, which President Obama supports. Companies that move goods are smart for reducing their carbon liability in advance of any law.