Consumers concerned about food miles might want to consider the impact of driving to the supermarket and back to do their shopping, a report on food miles suggests.

A report entitled “The Validity of Food Miles as an Indicator of Sustainable Development,” compiled for the Department of Environment, Food and Rural Affairs in the United Kingdom, shows that although trucks have the greatest negative impact on the environment in terms of air quality, carbon dioxide emissions, and noise, the social cost is not as great as that of cars, which cause more congestion and accidents.

Larger vehicles have made trucking more efficient, while a trend to shop at large supermarkets, rather than local shops, has contributed to more food miles traveled by car.

As David Granatstein, a sustainable agriculture specialist at Washington State University, points out, it’s far more efficient to carry 40,000 pounds of fruit on a 10,000-pound truck than to carry 50 pounds of groceries home from the store in a 3,000-pound car.

In terms of overall environmental impact, cars are the worst, followed by trucks, then vans, deep sea, and rail, the report calculates. The impact of air was not fully quantified. Some people believe shipping by sea is better than airfreight, but others say that for perishable goods, a quick journey by plane is better than refrigerating them for weeks on a cargo ship. In terms of just carbon dioxide emissions, air travel has less impact than trucks, cars, or ships, the report shows.

Rail was found to have very little environmental impact, since it emits no carbon dioxide. A new rail service provided by a company called Railex is being used by some Washington fruit packers to ship fruit across the country to Albany, New York.

John Botts at Dovex Fruit Company, Wenatchee, Washington, said his company is using Railex to try to reduce the number of trucks on the roads. Though only a small proportion of the fruit is shipped that way currently, he said there’s plenty of room for growth. The cost is about the same as for trucking, and it takes about the same time.