  The structure of the broad line region (BLR) is an essential ingredient in
the determination of active galactic nuclei (AGN) virial black hole masses,
which in turn are important to study the role of black holes in galaxy
evolution. Constraints on the BLR geometry and dynamics can be obtained from
velocity-resolved studies using reverberation mapping data (i.e. monitoring
data). However, monitoring data are observationally expensive and only
available for a limited sample of AGN, mostly confined to the local Universe.
Here we explore a new version of a Bayesian inference, physical model of the
BLR which uses an individual spectrum and prior information on the BLR size
from the radius-luminosity relation, to model the AGN BLR geometry and
dynamics. We apply our model to a sample of 11 AGN, which have been previously
modelled using monitoring data. Our single-epoch BLR model is able to constrain
some of the BLR parameters with inferred parameter values that agree within the
uncertainties with those determined from the modelling of monitoring data. We
find that our model is able to derive stronger constraints on the BLR for AGN
with broad emission lines that qualitatively have more substructure and more
asymmetry, presumably as they contain more information to constrain the
physical model. The performance of this model makes it a practical and
cost-effective tool to determine some of the BLR properties of a large sample
of low and high redshift AGN, for which monitoring data are not available.
