iSoul In the beginning is reality

# Characteristic speeds

In a sense every speed is a local conversion of space and time. But a characteristic speed (or modal speed) has the following properties:

(1) The speed is relative to a mode of travel or movement.

(2) The speed reflects the travel conditions of the mode, with or without additional conditions such as congestion.

(3) The speed serves as a general conversion between space and time for some region or universally.

Such a speed is characteristic, that is, it characterizes the mode and the travel characteristics. It may be a standard speed, such as the speed of light in a vacuum. It may be the free flow speed. It may be a typical speed, such as the average or mean speed of a mode of travel. It may simply be a reference speed, which is an estimated or conventionally used speed to relate distance traveled and travel time.

There is a corresponding characteristic pace (or modal pace), which is mathematically the inverse of the characteristic speed, but with units of space (length) instead of time. Speeds less than the characteristic speed may be called submodal speeds, and those greater than the characteristic speed may be called supermodal speeds. The best known examples are the subluminal and superluminal speeds, respectively.

The characteristic speed has previously been called the standard or reference speed but characteristic speed is a better term. Some previous posts may be edited accordingly.