TOKYO, Nov 9 (Reuters) - Drunk driving accidents in Japan almost halved compared to last year after a draconian new law was introduced in September in response to a series of fatal car crashes, showing that tighter rules can sober up drivers.

Under the revised law, drunk drivers can be jailed for up to five years or be fined up to 1 million yen ($8,900). The law punishes passengers who ride with a drunk and people who serve alcohol or lend a car to someone who may then drive under the influence.

A police report showed that after the law took effect, drunk driving accidents declined 41 percent year-on-year to 350 in a one-month period. The police also cracked down on 46 passengers of drunks and eight people who served alcohol to drivers.

But the message has yet to reach some drivers. In Nagano prefecture, central Japan, the number of drunk driving accidents during the same period doubled from the previous year, and five of the 14 drunk drivers were unaware of the new law, the Shinano Mainichi Shimbun daily said.

Japan has generally become more aware of the dangers of drunk driving due to a string of fatal accidents, including one last year in which three children were killed. The restaurant industry is also adapting to changing attitudes by handing out coupons to customers for cabs and chauffeur services.