$LDDrivingVelocities record is a list of Rule. The left side of the rule is the velocity function of the driving variable, while the right side is the corresponding substitution value . Example: {1[t]→1,...}
$DrivingVelocities record is appended to the LinkageData object by the ToTimeDependentLinkage function.
Only a constant velocity function assignment is allowed to the driving variables. If other function assignment is needed change the driving variables to the time variable (t) and express the driving variables as the function of the time.