calculate_travel_time() now uses terra::costDist() internally, removing the dependencies on the superseded raster and gdistance packages. Results are effectively the same; see the validation article for details of the small differences.
Cells that cannot be reached from any of points (e.g. because they are cut off by NA cells) are now NA in the output of calculate_travel_time(). Previously they were Inf.
calculate_travel_time() now drops (with a warning) any points that fall outside friction_surface, and errors if none fall within it.
calculate_travel_time() now works with a single point supplied as a one-row matrix or a one-point SpatVector. Previously these errored.
calculate_travel_time() and get_friction_surface() now correctly return the existing file when filename already exists and overwrite = FALSE, as documented. Previously they warned and then errored.
get_friction_surface() now fails gracefully, returning NULL with a warning, if the friction surface cannot be downloaded.