Aiming to reduce fuel consumption and CO2 emission a new navigation system called WAN has been developed. The system provides optimum route and engine revolution with constraints of schedule and seakeeping criteria. In this paper, simulations of a container liner on transpacific route are demonstrated using WAN. Weather data used here are composed of 8 items; significant height, period and peak direction of wind wave, significant height, period and peak direction of swell, and mean speed and direction of wind. Ship responses; i.e. ship speed, fuel consumption and vertical acceleration at F.P., are calculated based upon the enhanced unified theory. To optimize route and engine revolution the augmented Lagrange multiplier method is applied. The objective function of minimization is fuel consumption with constraints of the schedule and the service limit. From the simulations, the effectiveness of WAN resulted very high and it is shown that the reduction of the fuel becomes 26.1% on average. Concerning the schedule keeping, accuracy of weather forecast must be examined. The influence on the system is evaluated using two kinds of weather data; one is a forecast received at departure and the other is the dataset extracted from the sequential forecasts of every 24 hours. From the simulations it is found that the fluctuation of fuel consumption due to updating the weather forecast is much smaller than the reduction of the fuel by WAN. However, from the viewpoint of ship safety, it is necessary to execute the system again whenever the weather forecast updated.