A computer-implemented method carried out at a sensor apparatus affixed to a transportation asset of determining whether the transportation asset is in a loaded or an unloaded state, the method comprising detecting a trigger at the sensor apparatus, and in response to detecting the trigger taking a threshold number of samples of a displacement-related value of the transportation asset over time; determining that a variance of the threshold number of samples exceeds a first threshold; analyzing a frequency property based on the threshold number of samples, wherein the analyzing the frequency property comprises: determining a first bandpass filter output; determining a second bandpass filter output, the second bandpass filter having a higher frequency band than the first bandpass filter; determining an accumulated sum of squared value for the first bandpass filter output; determining an accumulated sum of squared value for the second bandpass filter output; and finding an energy ratio of the accumulated sum of squared value for the first bandpass filter output over the combined accumulated sum of squared value for the first and second bandpass filter outputs; and based on the frequency property, determining whether the transportation asset is loaded or unloaded, wherein the determining whether the transportation asset is loaded or unloaded comprises: finding that the transportation asset is unloaded when the energy ratio is less than a second threshold; and finding that the transportation asset is loaded when the energy ratio is greater than a third threshold. taking a threshold number of samples of a displacement-related value of the transportation asset over time; determining that a variance of the threshold number of samples exceeds a first threshold; analyzing a frequency property based on the threshold number of samples, wherein the analyzing the frequency property comprises: determining a first bandpass filter output; determining a second bandpass filter output, the second bandpass filter having a higher frequency band than the first bandpass filter; determining an accumulated sum of squared value for the first bandpass filter output; determining an accumulated sum of squared value for the second bandpass filter output; and finding an energy ratio of the accumulated sum of squared value for the first bandpass filter output over the combined accumulated sum of squared value for the first and second bandpass filter outputs; and determining a first bandpass filter output; determining a second bandpass filter output, the second bandpass filter having a higher frequency band than the first bandpass filter; determining an accumulated sum of squared value for the first bandpass filter output; determining an accumulated sum of squared value for the second bandpass filter output; and finding an energy ratio of the accumulated sum of squared value for the first bandpass filter output over the combined accumulated sum of squared value for the first and second bandpass filter outputs; and based on the frequency property, determining whether the transportation asset is loaded or unloaded, wherein the determining whether the transportation asset is loaded or unloaded comprises: finding that the transportation asset is unloaded when the energy ratio is less than a second threshold; and finding that the transportation asset is loaded when the energy ratio is greater than a third threshold. finding that the transportation asset is unloaded when the energy ratio is less than a second threshold; and finding that the transportation asset is loaded when the energy ratio is greater than a third threshold.