Kenmon, or checkpoints set up on major thoroughfares in Japan to help catch drunk drivers. He mentioned that drunk driving is a serious offence in Japan, and it is. Here's how serious:
Legally there are two classifications for driving under the influence of alcohol in Japan: 酒気帯び運転 (shuki obi unten) and the more serious 酒酔い運転 (sake yoi unten).
Charges Based on BrAC
Here's the TL;DR: Japan's drunk driving laws are strict. In many cases, a driver's license can be suspended or revoked based on the amount of alcohol consumed in a single can of beer.
Here are the details and the math: 酒気帯び運転 is the less serious offence. However, the law has been revised several times over the last decade, and each time this offence carries more points. As of 2009, there are two grades to this charge, carrying the following penalties:
If your breath alcohol content (BrAC) is over 0.15 mg/L (a blood alcohol content, or BAC, of about 0.03%*), it is a 13 point offence. If your BrAC is over 0.25 mg/L (a BAC of about 0.05%), it is a 25 point offence.
Assuming you had a spot-free driving record beforehand, a lone charge of 酒気帯び運転 (0.15 mg/L), or 13 points, would suspend your license for 90 days. If you had any other infractions within the last calendar year, a charge of 酒気帯び運転 by itself is enough for your license to be revoked.
The charge can of course be, and often is, compounded with other charges. Driving without a seat belt, driving without a license on your person, expired vehicle registration, running a red light, making an illegal turn, improper passing, failure to use turn signals, and speeding are all examples of offences that will bump up the number of points you receive. You only need 2 additional points on top of a BrAC 0.15 mg/L charge to guarantee revocation of your license for at least a year.
Any 酒気帯び運転 charge of a BrAC above 0.25 mg/L will mean immediate revocation of your driving privileges for at least 2 years.
But there's a basic formula used in estimating BAC:
BAC = (ml of drinks consumed * alcohol content of drinks) / (833 * your body weight in kg)
According to that formula, here's one rule of thumb: For an average 65 kg person, one 350 ml can of beer contains enough alcohol to exceed the minimum BAC needed for a 酒気帯び運転 charge in Japan.
Now, even though sixty-five kilos is a pretty realistic weight for an average adult male in Japan, to us fatty Americans, 65 kg sounds like a featherweight. But if that has you thinking you'd risk nothing to pop a can of light beer before driving home, don't hold your breath--literally. We've yet to talk about the other drunk driving charge: 酒酔い運転.
Charges Based on Appearance and Actions
The more serious of the two, 酒酔い運転 is a charge made at a police officer's discretion, and its issue is not dependent on a breathalyzer result. If an officer evaluates you as having impaired cognitive ability or as being unable to safely operate your vehicle and suspects alcohol as the cause, you may be charged with 酒酔い運転. It is a 35 point offence, meaning immediate revocation of your license for three years, regardless of your driving history. (An analogous but differently named 35 point offence is applied to drivers under the influence of mind-altering substances other than alcohol.)
The evaluation of your ability to drive can be made by the officer according to your speech, actions, responsiveness to questions, ability to perform simple tasks, etc. To ensure equal treatment of drivers, police departments use internal, predefined criteria when making these evaluations.
Refusing to take a breathalyzer test, by the way, is subject to a penalty of 500,000 yen or up to 3 months imprisonment. If you have not consumed any alcohol and simply refuse to cooperate with a breath test, you can be charged. If you refuse to take the test and the police still question your ability to drive, you could be charged with the more serious 酒酔い運転 anyway.
Japan's stance on drunk driving is clear: Don't do it. And the stiff penalties appear to yield results: Compared to over 26,000 accidents involving drunk drivers reported nationwide in 2000, there were less than 6,000 of such accidents in 2009.
In upcoming weeks, we'll be looking at some other driving-related topics.
*BAC and BrAC are essentially disparate; BrAC is only a somewhat accurate measure of BAC, the statistic that really matters, but it is used more in practice because it is easy to test for with breathalyzers. In the US and UK, the legal baseline for drunk driving is 0.08%, more than twice the leeway granted to Japanese drivers.