suspension motion while traveling over the road. Roughness
is measured as the accumulated suspension stroke normalized
by the total traveled distance. IRI is usually presented in engineering
units such as mm/m, m/km, or inc/mile. It is highly
correlated with acceleration of vehicle passengers (ride quality)
and tire load (vehicle controllability).11 Roads around the
world may have different names and visual characteristics, but
researchers can compare vibration analyses results for roads
with similar IRI.
3.5. Kurtosis of Vibration Signals
Kurtosis is the fourth statistical moment signal, known as a
global statistical parameter that is highly sensitive to the impulsiveness
of the time-domain data. For discrete data sets it
can be approximated by
K =
1
n4
Xn
j=1
(xj