OSAKA — People who take their dogs on long expressway rides can now give them some respite by unleashing them in grassy areas exclusively established for their pleasure.

These so-called dog runs have been flourishing since the government privatized the state-backed highway corporations in 2005. Since dogs face air- and train-travel restrictions, the new expressway companies are setting up canine rest areas at highway service and parking areas in an effort to increase profits.

West Nippon Expressway Co., which operates in the Kinki region covering Osaka and neighboring prefectures, and Chugoku, including Hiroshima, Shikoku and Kyushu, had only one dog run before the privatization. As of August, it had 22.

East Nippon Expressway Co., which covers the Kanto region, has six, and Central Nippon Expressway Co., which covers Nagoya, has four.

West Nippon Expressway Co. reportedly plans to diversify services at parking and service areas. While most of the dog runs are free, the company also plans to open the runs to local dog owners just to attract more customers.

Japan's falling birthrate has coincided with a rise in dog ownership. There were about 12.52 million dogs last year — more than all the elementary and junior high school populations combined, according to the Pet Food Manufacturers Association Japan.

Three dogs were seen frolicking at the Miki service area on the Sanyo expressway in Hyogo Prefecture one afternoon this summer. The field, replete with shade trees, is surrounded by a fence.

Shinichi and Hisae Abo, a couple in their 30s who own a miniature poodle, said they check on available dog runs before taking trips and always stop there.

Honda Motor Co.'s Web site Honda Dog offers information on inns where dogs can stay with their owners and other events.