  Effective spectral functions of the $\rho$ meson are reconstructed by
considering the lifetimes inside different media using the hadronic transport
SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). Due to
inelastic scatterings, resonance lifetimes are dynamically shortened
(collisional broadening), even though the employed approach assumes vacuum
resonance properties. Analyzing the $\rho$ meson lifetimes allows to quantify
an effective broadening of the decay width and spectral function, which is
important in order to distinguish dynamical effects from additional genuine
medium modifications to the spectral functions, indicating e.g. an onset of
chiral symmetry restoration. The broadening of the spectral function in a
thermalized system is shown to be consistent with other theoretical
calculations. The effective $\rho$ meson spectral function is also presented
for the dynamical evolution of heavy-ion collisions, finding a clear
correlation of the broadening to system size, which is explained by an observed
dependence of the width on the local hadron density. Furthermore, the
difference in the results between the thermal system and full collision
dynamics is explored, which may point to non-equilibrium effects.
