Buffer area and its role in optimization of flow of automatically controlled trucks at merging areas of motorways

This paper discusses the operation of automatically controlled trucks (ACTs) on dedicated freight lanes (DFLs) as one of the major options for increasing the efficiency of freight. transport system on the existing motorways. It proposes using a kind of buffer area (a kind of calming area) to regulate the traffic flow of ACTs when approaching to the merging areas. In addition, some other functions such as overruling the mode of driving (from manual mode to automatic mode or vice versa) have been proposed. For optimizing the operation of ACTs, an optimization model has been developed to synchronize the speed and density of ACTs while approaching to the merging area. Results of the analysis show that the buffer area would help to decrease the interruption of flow of manually driven vehicles (MDVs) by ACTs and therefore will improve the average travel time of the ACTs for time periods when much interaction of ACTs and MDVs is expected. Increasing the capacity of the buffer area would not have a great influence on the average travel time of each ACT. They also indicate that the same amount of increase in capacity of the buffer area only improves the average speed of ACTs on the DFL by about 0.6 km/h. Therefore, finding the optimum capacity of the buffer area strongly depends on the level of demand and its variation in time.