PAVAS – Null Guidance Technique

This is an audible tone based system to guide the driver to an average speed. This is used in TSD and Regularity stages. This method greatly simplifies conveying the speed information to the driver and it is easily assimilated.

The first part is that if the driver is less than the desired speed, a low tone of 800 hertz is used. If the speed is greater than the desired speed, a tone of 2000 hertz is used. Now as the speed approaches the desired speed, the mark to space ratio of the tone decreases. If the speed is 30 kph away from the desired speed, then the mark to space ratio is 1.0 which results in a solid tone. As the range decreases so does the mark to space ratio and it falls until 0.1 which results in a short “pip” sound. In both situations of under or over speed, the driver can tell he is getting closer and what he has to do to reach the desired speed.

On the under speed condition, if the vehicle gets very close to the desired speed, the the tone does not sound. This called the dead zone. If the vehicle is over speed, there will always be a tone.