Understanding modular organization between brain regions can provide deeper insight into the complex neural mechanisms associated with processes like vigilance decrement. Distinct but interacting modules in brain connectivity networks have been known to support integration of specific mechanisms relevant in high-order cognitive processes. To investigate the neuronal mechanisms associated with vigilance decrement, we conducted an experiment where the participants performed a driving task. EEG graph metrics within communities, like clustering coefficient (Cintra), efficiency (Eintra), density (Dintra), and between communities, like intermodule density (Dinter), were computed from the source-localized surface brain signals. Further, we also calculated the nodal out degree to investigate the difference in information flow in the brain during vigilance decrement. Increase in the intermodule density, Dinter, was observed from the left fronto-parietal cluster to the right temporo-parietal cluster. Moreover, significant reduction in the intramodule metrics, Eintra and Cintra was observed in the right temporo- parietal cluster. Thus, our findings signify a flexible topographical architecture to compensate the hub disruption effect caused due to decline in vigilance.