As multi-lane roadways have been widely used in many countries for years, analysis of two-dimensional vehicular interactions acquires special importance in highway design and operation. The simultaneous consideration of both lateral and longitudinal movements of traffic flow becomes vital in many aspects of traffic engineering, like modelling. The former component was reviewed elsewhere. In this paper, previous work on longitudinal characteristics of multi-lane traffic flow is scrutinised. Non-existence of such a review in recent literature was the main motive of the work, and it is hoped that it forms a reference report for other traffic analysts. In addition, the paper underlines a number of possible areas for future research.