  In this work we study the competition and correspondence between the
classical and quantum routes to intramolecular vibrational energy
redistribution (IVR) in a three degrees of freedom model effective Hamiltonian.
Specifically, we focus on the classical and the quantum dynamics near the
resonance junctions on the Arnold web that are formed by intersection of
independent resonances. The regime of interest models the IVR dynamics from
highly excited initial states near dissociation thresholds of molecular systems
wherein both classical and purely quantum, involving dynamical tunneling,
routes to IVR coexist. In the vicinity of a resonance junction classical chaos
is inevitably present and hence one expects the quantum IVR pathways to have a
strong classical component as well. We show that with increasing resonant
coupling strengths the classical component of IVR leads to a transition from
coherent dynamical tunneling to incoherent dynamical tunneling. Furthermore, we
establish that the quantum IVR dynamics can be predicted based on the
structures on the classical Arnold web. In addition, we investigate the nature
of the highly excited eigenstates in order to identify the quantum signatures
of the multiplicity-2 junctions. For the parameter regimes studies herein, by
projecting the eigenstates onto the Arnold web, we find that eigenstates in the
vicinity of the junctions are primarily delocalized due to dynamical tunneling.
