PAVAS - Alarm Speed Menu

This menu is used to warn the driver of the proximity of the Alarm (Over speed) limit. The menu operates with three alarm set points, Low, Alert and Alarm.

The first set point is the Low Speed Alarm. When the vehicle is less than this speed set point, there is no tone. Once it reaches this level, an audible tone occurs. The tone is quite complex and consist of three parts. The first part is the frequency which commences at 300 Hz and rises to 3000 Hz. The second part is the duration of the tone which is called the Mark to Space ratio. This essentially changes the length of the tone relative to the duration. The duration is the rate at which the tone is repeated. As the speed rises, the frequency and the Mark to Space ratio increases and the duration decreases. The net effect is that the tone become more strident as the vehicle approaches the Over Speed or Alarm limit. The Low Speed limit is often used in transport stages to avoid accruing penalties when traveling between stages.

The second limit is the Alert level. The object of this set point is to alert the driver to the onset of an over speed condition. Event experience has shown that there is a given reaction time for the driver to cease accelerating before reaching the over speed condition. This is highly subjective and depends on the vehicle dynamics, the driving style and the driver's reaction time. Typically, this Alert limit is set a few kph below the Alarm level. When the vehicle reaches the Alert level, the tone changes to a warble similar to an Emergency vehicle siren. It alternates between a frequency of 1000 and 1800 Hz.

The final set point is the Alarm or Over Speed tone. When this speed is reached the tone sounded is a fixed frequency of 3000 Hz and constant duration. There is a separate programmable volume level for this tone since it usually occurs at high vehicle ambient noise.

The menu displays the vehicle speed and text for Safe, Caution, Alert and Alarm conditions

Another function that is useful is the ability to display the distance traveled on the stage after the Alarm Speed Menu has been entered. The distance display activated by pressing the Left or Right buttons. Pressing the buttons again reverts to the speed display.

This display can also be used to calibrate the Wheel Pulse distance by driving over a calibrated distance and comparing the distance displayed to the known surveyed distance. A simple ratio of the current Wheel Pulse distance by the calibrated and measured distance gives a corrected Wheel Pulse Distance. This can be entered into the Wheel Distance Direct menu. This provides an alternative method to the Calibrate by Survey Distance menu