Using the sample data obtained from a group of pedestrian experiments,a function formulating the velocitydensity relationship of pedestrians and linear regression is proposed to provide empirical evidence for the lookahead behavior of pedestrians in bi-directional flows.We find that the velocity of pedestrians is negatively correlated with not only the densities of the opposite-direction and the identical-direction pedestrians around them but also the densities of the same-direction pedestrians ahead of them.Moreover,the movement of pedestrians is most affected by other pedestrians moving in the same direction about 1 m ahead.