In Italy and Switzerland, fleets of trucks carrying milk and dairy products, heating oil, and groceries all use ant-foraging rules to find the best routes for deliveries.

And then Mr. Kimura, 48, says there are the little things that his family of four does to squeeze fuel bills, like reusing warm bath water to wash laundry and bicycling to buy groceries.

On his cheap motorbike taxi, named after a once-admired no-frills domestic airline of the past, he often carries an entire family or a week's groceries, ducking and weaving through the traffic.