In order to investigate the influence of the forecast information provided by ATIS on the traffic flow evolution of the degraded road network, a weighted moving average based travel time forecasting method is designed, and the path update rule is established in the forecast information environment. The proposed route update rule is used to analyze the effects of prediction information dependency parameters, information quality parameters, weight parameters and network degradation degree on traffic flow evolution for a small test network. The results show that: 1) there is a threshold value for the dependence of travelers on the predicted information in the information environment, when the dependence is less than this value, the traffic flow quickly evolves to a stable state, and when the dependence is greater than this value, the network traffic flow will oscillate; 2) there is a situation where the higher the quality of the predicted information provided by the information system, the worse the traffic flow evolution; 3) for a particular degraded network, there is a certain optimal combination of weights that can be used to guide the release of forecast information of the network; 4) the smaller the degradation of the road network, the greater the role played by the forecast information.