Unmanned truck columns will save time and up to 20% of fuel

Researchers predict that unmanned trucks should enter the transport system in the coming years. They also suggest that autonomous vehicles can save fuel if they move in columns of several trucks each. Like flocks of birds or wedges of fighters, groups of bikers and racing cars, trucks have less aerodynamic resistance when moving at close distances.

But the creation of a column of cars to deliver goods between distribution centers or the transport of passengers between stations takes time. A car that arrives at the station earlier has to wait for the others before they form a convoy and hit the road, which creates inevitable delays.
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Columns of trucks that travel close to each other to achieve aerodynamic efficiency can save up to 20% on fuel costs. The more cars in one convoy, the higher the efficiency: the first and the last truck in the convoy are not affected by the aerodynamic shadow effect. MIT engineers have found that there are two effective options: either build a convoy of vehicles from those that already exist and send out on a schedule, or send a specific number of vans in one convoy once.

The movement of vans in close proximity to each other increases fuel efficiency. Columns of trucks, flocks of birds and wedge fighters - similar groups from a system point of view. People who study these systems only look at performance indicators, such as time delay and fuel consumption. Scientists from MIT consider these indicators in comparison with the cost, energy consumption and environmental impact. According to them, this line of research can really improve the efficiency of transportation.

According to the engineers, during the trucking, especially over long distances, a significant part of the fuel is spent, including on attempts to overcome aerodynamic drag. Previously, scientists calculated that if several trucks would go several meters apart, one after another, the cars in the middle should experience less resistance, thereby saving 20% ​​of fuel.

Those vans that go behind should save about 15% of the fuel - a little less because of the air currents that form in the rear. A convoy of five trucks will save about 17% of fuel compared to single trucks, eight cars will give 18% savings and with only 15 vans in one convoy the efficiency will reach 19%.

Associate Professor of the Department of Aeronautics and Astronautics MIT Sertak Karaman (Sertac Karaman) and his colleagues developed a mathematical model to study the impact of various policies for planning fuel consumption and delays. Together they modeled a simple scenario in which several trucks move between two stations and arrive at each one at random times. The model includes two main components: a formula for representing the time of arrival of the vehicle and for predicting fuel consumption.

The group observed how arrival times and fuel consumption change in two planning strategies: a timetable policy in which vehicles, regardless of their number, form a convoy and depart at a specific time; and feedback policy when trucks hit the road only when a certain number of cars are typed - a strategy with which Karaman first met in Turkey.

“I grew up in Turkey, where there are two types of public transport: regular buses, which run at regular intervals and others, where the driver will stop at a bus stop until the bus is full, and then go on the road,” he notes.

In the process of creating models of movement of convoys of freight transport, researchers analyzed a variety of different scenarios within the two main directions of traffic planning strategies. In order to assess the impact of the schedule on the movement, they modeled scenarios in which the columns were sent at regular intervals, for example, every five minutes, and compared them with options at other intervals of three and seven minutes. In accordance with the feedback policy, they compared scenarios in which different numbers of cars were sent — first three at a time, then five at a time.

Ultimately, the team found the optimal ratio in which moving from one point to another will take the least time while maintaining a larger amount of fuel. Those columns that went on a specific schedule, proved to be more effective than those that were separated in time. Similarly, feedback scenarios, in which a certain number of trucks were first assembled before departure, were more optimal than those in which the number of trucks in the convoy was constantly changing. The study also revealed that the feedback policy is slightly more stable than the strategy using the timetable - with the first one you can save 5% more fuel.

Karaman now works with transport companies in Brazil, where he creates models for the efficiency of freight transportation for them. Its not yet final version assumes the movement of cars at a very close distance - from 3 to 4 meters, which will maximize aerodynamic efficiency. It is difficult for an ordinary person to maintain such a distance behind the wheel of a truck, so Karaman assumes that autonomous driving systems will be required.

Unfortunately, the study can not cover all aspects of freight. It did not consider the reaction of other motorists who are not part of the column. It is likely that drivers will not be delighted with the movement in one stream with autonomously controlled trucks, despite the fact that the latter can potentially be safer. Unmanned trucks will be equipped with an automatic control system and security algorithms in case they have a flat tire or a malfunction is detected. The first autonomous cars will be under the control of drivers, but gradually his role in driving will come to naught.

When trucks are heavily spaced in such a way that, if desired, a person can travel between them - this is one thing. However, the solid walls of the truck with a length of several hundred meters discouraged: a column of 10 trucks with a fuel economy step of 3-4 meters will stretch about 230 meters.