Dear Alice,

I was more than a little shocked, upon moving to Japan last year, to see people riding bicycles on sidewalks. Back in Arizona, in the United States, sidewalks are for pedestrians, and it's illegal to ride a bike on one. Each time I ride my bike in Tokyo I wonder if I'm breaking the law. A friend told me it's OK to cycle on either the road or the sidewalk, but another said riding on the sidewalk is only permitted where there are signs that say so. I don't think I've seen such a sign and am not sure I'd recognize one if I did. What the heck are the "rules of the road?" (Or should I say "sidewalk?")

Mark J., Tokyo

Dear Mark,
Your second friend is correct. Sort of. Officially, cycling is permitted on sidewalks only where there is a sign that says it's OK, and you could be cautioned or ticketed by the police for riding on a sidewalk anywhere else. Unofficially, the situation is more complex. You're unlikely to get in trouble with the police for riding a bicycle on any sidewalk in Japan, but it could depend on how you're riding and the discretion of the officer who sees you. How's that for a definitive answer?

There is indeed a sign that permits bicycles on sidewalks, but I'm not surprised you're unfamiliar with it. I've been biking around Tokyo every day for six years, but until I got your question I had never noticed one. Known (to an official few) by the unwieldy moniker of jitensha oyobi hokosha senyo doro hyoshiki (bicycle- and pedestrian-use only road sign), it's a blue circle with a silhouette of an adult man walking with a child, and below and to their right, a bicycle.

Until about 1970, when these signs first started appearing, it wasn't permitted to ride on sidewalks at all. But the rapid increase in the number of automobiles during the first postwar decades forced bicyclists up onto the sidewalks for sheer safety. Traffic was chaotic, and there were few of the safeguards we take for granted today, like guardrails and pedestrian lights. Readers who were in Japan in the '60s and '70s may remember the term kotsu senso (traffic war), coined when traffic fatalities first exceeded the number of Japanese who were killed in the Sino-Japanese war. Dangerous traffic became a social issue, and one strategy to reduce deaths was to change the law to allow bicycles on designated sidewalks.

The trouble with that is that pedestrians and bicycles move at different speeds, and forcing them to share the same space increases the likelihood that they'll crash into each other. In 2005, there were 2,435 collisions between bicycles and pedestrians in Japan that were serious enough to be reported to the police. In six of those accidents there was a fatality.

Other countries have reduced traffic fatalities by providing separate space for motor vehicles, bicycles and pedestrians, but Japan has been slow to adopt the idea of dedicated bicycle lanes, partially because of a lack of space. Not surprisingly, riding a bicycle in Japan is a lot more dangerous than in other developed countries. According to data from the International Road Traffic and Accident Database, more people die on bicycles in Japan than in Germany, France, Italy and the Netherlands put together. Japan also has far more cycling fatalities than the U.S., despite having less than half as many people.

The National Police Agency recently held a symposium on how to make cycling safer. The attitude of the police representatives, according to one participant, was that bicycles should be moved off the roads completely, even if they've got no other place to go but straight into pedestrians' paths. This is one reason why I say you're unlikely to get stopped by the police for riding on a sidewalk, even where it isn't permitted. They like you there. Another reason is that all the police officers I spoke to assured me they look the other way unless the cyclist causes an accident or is doing something else illegal.

That's a good reason to learn the other rules concerning bicycles. Japanese law defines a bicycle as a conveyance for one person, although an adult is allowed to carry one child up to the age of 6, as long as the child is in a seat designed for the purpose. Which means all those moms who ferry two kids at once are breaking the law. So are the high school students and lovey-dovey couples who engage in flagrant futari nori unten (two people on one bike).

You'd never know it from casual observation on a rainy day, but kasasashi unten (riding with an open umbrella) is also against the law in Japan. So is doing anything that impairs your ability to operate the bicycle safely, including talking on a mobile phone. But except for occasional crackdowns on riding at night without a light, the police rarely go after cyclists. They're certainly not likely to chase after a mama chari (mommy bike) because there are two kids aboard.

However, the law against inshu unten (driving under the influence of alcohol) applies to bicycles too, and while rare, there have been arrests for drunk riding. So it's a good idea to walk your bike home after hitting the bottle. Just be sure to stay on the sidewalk, and watch out for plastered pedestrians!