With quiet car solutions being considered by both Congress and NHTSA, the new Guidelines adopted by the Japanese MLIT on Jan. 29, 2010 are extremely relevant.  The Unofficial English version of the Guidelines are as follows:

Automobile Approaching Notification System

1. Definition

Notify pedestrians that automobile is approaching.

2. Operating condition

(1) Sound method
 - System works automatically from 0 to 20 km/h.
 - It is not needed when internal combustion engine is running.
 - It is not needed when backup alarm is operating.
(2) Temporary OFF switch
 - Temporary OFF switch may be installed but telltale is needed.
 - Default position is ON.
 - Switch is visible to driver.

3. Type of sound and volume

(1) Sound shall suggest automobile driving condition and shall be continuous. Following sounds are inappropriate.
 - Siren, chime, bell and melody
 - Audible warning device (horn)
 - Cry or scream of animals and insects/bugs
 - Natural sound such as wave, wind, flow of river
 - Any other sounds that can not suggest automobile.

(2) Produced sound shall change volume and interval/step in accordance with driving speed so that pedestrian can detect easily.

(3) Sound volume shall not exceed a level in which ICE vehicle is running at 20km/h.