Freeway traffic congestion and associated delays have become a serious problem throughout much of the world. Among factors studied in relation to this congestion, lane-change maneuvers (LCMs) are suspected to be one source of traffic delay. Little empirical research has been done on this topic despite how common the lane-changing process is on multilane roadway segments. Two main problems hinder research: first, it is difficult to distinguish changes in delay caused by LCMs from that of a preexisting delay caused by a queue; second, quantifying LCMs is difficult because it requires both spatial and temporal coverage. This paper presents the concept of delay caused by LCMs and proposes a method to estimate such delays within a given lane relative to the situation in which no LCMs have taken place. This estimation method makes it possible to investigate the impact of LCMs on traffic delays based on vehicle trajectory data, which record the time and location of each vehicle at each instant. This preliminary study shows the effectiveness of the proposed method to estimate delays caused by LCMs and reveals how LCMs affect delays on congested freeway segments.