When traveling to an emergency ambulances in Tokyo, in addition to using the siren, also have a loud hailer calling out a warning in Japanese. Faye assures me that the is just a very politely phrased warning to other road users to get out of the way. Wanting to know more, I again resorted to Mr Google and came up with this (complete with Japanese translations).
In Tokyo traffic doesn’t so much flow as tick forward in carefully negotiated increments. Cars, trucks, buses and cyclists sidle past each other, often with just centimeters to spare, and streets are regularly packed beyond capacity. This can make it difficult for drivers to get out of the way of emergency vehicles, so ambulances are outfitted with kakuseiki (loudspeakers) that allow the crew to communicate their intended movements and help them orchestrate passage.
Some ambulances are fitted with recorded alerts that play automatically when the turn signals are used: “Kyūkyūsha ga migi e magarimasu” (“The ambulance is turning right”) and “kyūkyūsha ga hidari e magarimasu” (“The ambulance is turning left”). But everything else is called on the spot as the crew deems necessary.
Here are some phrases you’re likely to hear: “Aka shingō o tsūka shimasu node chotte mate kudasai.” (“We’re going through the red light so please wait a moment”); “hantai shasen o tsūka shimasu” (“We’re passing through the lane for traffic in the opposite direction”) and “Kyūkyū sharyō gap sekkin shimasu node yukkuri to hidari e yotte kudasai” (“An emergency vehicle is approaching so please make your way slowly and carefully to the left”).
Japanese ambulance crews tend to use relatively polite language, in part so drivers will respond calmly as use of the meirei-kei (the imperative form) could startle drivers and lead to additional accidents.