Honda has updated its domestic market navigation system to warn drivers of heavy rainfall ahead on roads - and earthquakes.

The new system will first appear on the redesigned Fit (Jazz) subcompact on sale in Japan later this year but there are no plans so far to offer it overseas, executive Manabu Nishimae told the Associated Press (AP) at a media event in Japan. "We believe information services are an important part of a car's quality," he added.

The service is free, but drivers pay mobile phone bills for relaying data. Data transmission cards for a set monthly fee of about $US8 (GBP4) are available for frequent users. About 530,000 drivers use the current navigation service in Japan, or about 40% of Honda owners, AP said.

With the latest upgrade, e-mail warnings will be sent to a pre-assigned address when a car with the system is in an area of a strong earthquake - handy in a quake-prone nation. If heavy rain is forecast on a planned route, icons of exclamation marks pop up on the monitor, the report said.

Honda has also upgraded its map system so updates take just a few minutes to download - until now, disks with map data had to be changed.

Tokyo-based Honda told the news agency it had found a way to compress data so that portions of a map, such as new roads, get relayed piecemeal. On average, driving time is cut by 20%, according to the automaker.

A feature of Honda's new system is that it collects information from individual Honda cars on the road. For example, in the new earthquake notification service, the system will be able to show which roads have been shut down, AP said.

This kind of detailed information could even tell drivers exactly which lane of a freeway is congested, general manager Takeshi Imai told the news agency.