VISIR-1.b is a routing model for computing optimal and safe ship tracks by means of a graph-search method. The current version accounts for both waves and ocean currents. Furthermore, both static (bathymetry, shoreline) and dynamic safety constraints (vessel intact stability) are considered. This code release is organized into a "production code", employed for computing least-time tracks, and a post-processing suite, for assessing the energy efficiency gains of the optimal tracks with respect to least-distance tracks. Please refer to the ReadMe.txt for further information and code installation procedure. The code version refers to the gmd-2018-292 manuscript (Mannarini G. and Carelli L. 2019. VISIR-I.b: waves and ocean currents for energy efficient navigation. Geoscientific Model Development Discussions, https://www.geosci-model-dev-discuss.net/gmd-2018-292/ (under review)).  Please refer to https://doi.org/10.5281/zenodo.2556801 for additional datasets relative to Figures in  gmd-2018-292 .