The recent percolation of autonomous technology in the passenger vehicle segment, in the US, Europe, and some parts of South-East Asia, has garnered a lot of attention. Any news regarding the safety of riders in an autonomous vehicle or the safety of vulnerable road users in its vicinity makes it to the news quite easily. However, the sequence of propagation of autonomous technology in different industry segments is often overlooked. The fact that some industries are in need of going driverless sooner, needs to be taken into account. Trucking is one such space where per reports, the US is short of 50,000 drivers.
In any of these industries, autonomous technology is being embraced incrementally. While partial automation has its advantages, connected vehicle technology is also helping solve some pertinent issues. One such application of connected vehicle technology in the trucking industry is platooning.
Platooning means a tight coupling of vehicles moving together in a convoy. Simply stated, when all following vehicles mirror the motion profile of the leading vehicle in a convoy, then the arrangement is called a platoon. Overall fuel consumption reduction of around 4% to 15% is reported using platooning, owing to reasons like lesser braking, smoother motion profiles for higher number of vehicles, and a decrease in air drag.
This article talks about Wipro’s approach to platooning as a solution, concerns that justify the need for platooning, and the nuances of its application on public roads.
Platooning – the need
Trucks have posed serious safety concerns for other road vehicles. The weight of trucks is 20-30 times the weight of other passenger vehicles. When fully loaded, a tractor semi-trailer combination can weigh up to 80,000 pounds. Per US FHA regulations, in case of a grandfathered tractor-semitrailer combination, the size of the trailer has to be within the range 14.53meters (Alaska) to 18.14 meters (Oklahoma, Louisiana).
Despite all the stringent regulations around the movement of trucks, they pose a very serious threat to the safety of other entities on roads. In 2018, 4136 people died in truck crashes. Longer stopping distances lead to rear-end crashes in trucks. Loading the trailer improperly or not securing the cargo well, leads to shifting cargo, resulting in dynamic weight distribution changes in the truck. Jack-knife incidents in trucks and rollovers are major highway safety concerns.
Recent statistics show that 15,000 commercial trucks experience rollover every single year—averaging about one rollover for every million miles of truck travel. Per IIHS, Electronic Stability Control (ESC) has been required on all new truck tractors and buses since Aug. 1, 2019. ESC on large truck tractors and large buses will prevent 40 to 56 percent of rollovers.
Jack-knife is the phenomenon in which the trailer spins across various lanes before coming to a stop. The chances of a jack-knife occurring increase by 49% if the speed of the truck increases by 10 miles per hour.
Nevertheless, technology adoption in the trucking industry is likely to improve the situation. Per IIHS reports, a combination of Forward Collision Warning, Lane Departure Warning, Blind Spot Detection, and Electronic Stability Control could prevent or mitigate 107,000 police-reported crashes each year, representing 28 percent of all crashes involving large trucks.
Connected vehicle technology absorption in the form of platooning in the trucking industry is showing its impact on fuel consumption as well as pressing safety aspects, highlighted above.
Platoon – the types
Logically, platoons can be divided based on whether the trucks in the platoon are all the same type, bobtail trucks or tractors with one semitrailer or truck with a centre axle trailer etc., in which case, the platoon will either be heterogeneous or homogeneous.
Platoons also, may be of trucks that start and/or end together, or trucks that come together in the middle of a journey and if both have the same technology deployed, or can follow the same protocol, they may form a platoon on the way. In the latter, the concern is about standardization of communication protocol between trucks.
Platooning – the technology
Longitudinal movement control and lateral movement control are two important aspects of platoons. If a platoon were to start and end together, and from the beginning of platooning to the end, be on the same stretch of road, then the trucks in the platoon could be on the leftmost lane (in a right-handed driving system). These trucks could possibly continue to be in the same lane using lane-keep assist technology, and break the platoon only when they exit the particular stretch of road. This ensures that a platoon exists, within a plethora of constraints, notably without any lateral movement.
Today, platooning technology is advanced enough to not limit the operations of a platoon to only longitudinal movement but rather the lateral movement scenarios and corner cases are baked into the solution. This is enabled by vehicle-to-vehicle connection technology, and an overarching vehicle-to-network connectivity.
Formation of the platoon
Any trucks that need to be part of the platoon are connected to the network. Their location is known to a central cloud, which essentially enables each truck driver to have a view of where any other trucks are in the range of a few tens of miles. If any truck driver observes another truck on the same route, a direct conversation with the other truck driver can help him/her ascertain till where the common stretch of road is, and if the other driver also wants to be in a platoon. Once there is agreement, either the truck that is behind can accelerate or the truck that is ahead can choose to decelerate or wait at a roadside halting area. These trucks can then start moving together once they are within a few feet from each other. The prescribed distance between two trucks in any such convoy is 70 feet. In forming this convoy, the leading vehicle (LV) which is in front and the following vehicles (FV), communicate with each other through V2V technology. The leading vehicle controls the following vehicle; there is communication on the velocity, acceleration, and braking data points, but any following vehicle also retains a certain amount of control on itself.
Scenarios or corner cases – temporary breakage in the platoon
There are several scenarios where the platoon may need to break or temporarily disengage and then quickly re-establish the coupling:
- When a vehicle in an adjacent lane wants to cut through the platoon, for taking a highway exit (Refer figure 1): In this case, there will need to be communication initiated by the Leading vehicle to temporarily break the platoon to make space for the vehicle in the adjacent lane to take the exit. Once the vehicle has taken the exit, the platoon can reform.
- When there is a slower vehicle in front of the platoon, slowing down the whole convoy (
Refer figure 2): the convoy will need to change lane, depending on availability of vacant slot in the adjacent lane, one or more vehicles will keep breaking out and moving ahead of the vehicle in front of the convoy. If ideally there isn’t enough space for the entire convoy to change lane together (in case of more than 2-3 vehicles) then the last vehicle of the convoy may have to break first followed by the vehicle in front of it and so on.
- When a particular vehicle in the convoy itself needs to take an exit: Depending on which lane the platoon itself is in, the vehicle from the platoon that needs to take the exit, will communicate on this upcoming exit to the leading vehicle in advance. The leading vehicle will communicate with the platoon to create gaps for this vehicle to take the exit or move to the right lane (in a right-handed traffic), thus temporarily breaking the platoon. As soon as the vehicle is out of the platoon’s lane, the platoon reforms.
- When there is a lane merger ahead because of accident or road maintenance activities: In this scenario, a traffic congestion situation will be anticipated and so the platoon will break in the interim until the lane merger is complete.