The paper provides a detailed analysis of the impact of automated vehicles using eco-cruise control system on the traffic flow. The speed profiles of vehicles using eco-cruise control system generally differ from those of conventional human-driven vehicles. The characteristics of the traffic flow on macroscopic traffic level combine both automated and human-driven vehicles. In the simulation-based analysis the effects of traffic volume and the ratio of the automated vehicles are in the focus. Based on the results the analysis an extension of the eco-cruise control is also proposed, in which the balance between the traffic flow and transport efficiency is achieved.