The computer simulation model which has been developed for the study of traffic delays at a T-junction can be varied to accommo date a single-lane or dual-lane approach on the minor road and to allow the major road to be either a single or dual carriage-way. In the latter case, the amount of waiting space for right-turning vehicles within the central reserve is also variable. The simulation enables the traffic engineer to estimate the economic value of improving the traffic-handling capacity of a T-junction.