The exclamation mark ! means that there has been no communication with the device for the past two minutes. The driver is logged in, but the GPS data is not reaching our servers.
The asterisk sign * means that the the device is providing GPS data, but it is not stable and/or is of very poor quality.
These Icons appear after 2 minutes to allow time for momentary dips in signal, such as driving through a tunnel, low lying ground or in heavily built up areas with tall buildings.