The change in estimated TTC as a function of the change in L_AeqOcc on a given trial n, relative to the TTC and L_AeqOcc presented on the preceding trial n − 1, in the blocks with trial-to-trial variation in sound power. The changes were calculated between pairs of consecutive trials. The colors of the individual datapoints show the vehicle sound power of trial n. The solid black regression line was fitted based on data from pairs of trials with a decrease in L_AeqOcc (L_AeqOcc(n)< L_AeqOcc(n − 1)). The dashed black regression line was fitted based on data from pairs of trials with an increase in L_AeqOcc(L_AeqOcc(n)≥L_AeqOcc(n − 1)). Lastly, the gray regression line was fitted to all trials from the condition with trial-to-trial sound power variation.