Follow the leader

Thinking Highways
By Rick Sterrett May 13, 2014 15:44

Follow the leader

A platooning example

What if we could reduce fuel consumption, road congestion and driver fatigue all at the same time? The technology is evolving that will do just that and it’s called platooning. The bigger question is will our governments and the insurance industry permit this technology innovation to blossom? Rick Sterrett reports,

A platoon, or convoy, of vehicles is a collection of vehicles that for some period of time under coordinated control drive closely together along the same path. They are sometimes called road trains. It should be led by a professional driver in a lead vehicle and be closely – and safely – followed by other vehicles. In many prototype scenarios the lead vehicle would typically be a truck. The following vehicles could be cars or trucks, although the order of vehicles is important to get safe and optimal performance. Drivers in the following vehicles would relinquish control of their vehicle once the platoon is formed. Software in the vehicles measures the distance, speed and direction and adjusts to those vehicles in front. However, the following vehicle drivers would need to be able to take control of their vehicle quickly when the platoon dissolves.

There are two basic reasons to form or join a platoon.

  1. Improved Fuel Economy – As vehicles drive closer together in the same direction the wind resistance for all the vehicles is less. The fuel required to move the car the same distance at the same speed is less for a vehicle in a platoon. This fuel economy savings varies by platoon make-up, vehicle type and weight, speed, terrain, and especially by following distance. A California PATH Research report published in October 1995 showed that four vehicles traveling in a platoon one vehicle length apart could reduce the total amount fuel used by 10 per cent. This is precisely why trucks form informal un-automated convoys on our highways today.
  2. Reduced Driver Fatigue – Drivers in following vehicles that are engaged in a platoon don’t have to be actively engaged in piloting their vehicle. However, they still must be ready to quickly take control of their vehicle if the platoon dissolves in either a planned or emergency fashion. Long haul truckers are limited from driving more than 11 hours in a 24-hour period by the US Federal Motor Carrier Safety Administration (FMCSA). This could change in the future if the US Government could be convinced that truck driver’s fatigue is reduced when “driving” a following vehicle in a platoon. If trucking companies can transport their freight with less mandated rest stops, they will save significant amounts of money.

Platoons also lessen road congestion by reducing both the average space between vehicles and the lag time required to match changing speeds in heavy traffic.

CONSIDERATIONS

While the reasons in favor of platooning are straightforward, there are several operational and technical challenges to forming, operating and dissolving platoons.

Formation: To form a platoon all the vehicles must negotiate and answer the following questions:

  1. Where and when is the platoon initiated and dissolved?
  2. Who is going to lead?
  3. How many vehicles in the platoon?
  4. What is the order?
  5. What are the financial arrangements?

Communications: Once the platoon is formed, there is constant communication between the lead vehicle and all followers. The lead vehicle controls the speed of the platoon and therefore all the individual vehicles’ speeds in the platoon. It also controls the “steering” so that all vehicles stay in line through curves, turns and lane changes. The communications for this control (both steering and speed) require guaranteed control message delivery and millisecond responses to assure that the vehicles in the platoon don’t collide.

Control: Each following vehicle will require some sort of adaptive cruise control system that will be operated by the lead vehicle automatically. Additionally, each following vehicle will also have some sort of automated steering that can be controlled by the lead vehicle. The lead vehicles’ steering and speed will be the guide for the rest of platoon, so it must have built-in sensors and the intelligence to relay the commands to following vehicles. As part of the adaptive cruise control systems, the following vehicles will need sensor systems, typically radar or lidar, which accurately measure the distance between the vehicles in a continuous and automatic process. The control algorithms needed to form a platoon, keep it together and dissolve it safely will be very complex. Remember the closer the vehicles can be to one another, the more fuel you can save. The control algorithms must also take into account emergency situations. What happens if a following vehicle gets a flat tire or has some other kind of mechanical problem?

There are also financial hurdles to overcome. The technology will not come cheap at first. Some of the required equipment, such as adaptive cruise control, is becoming a common option in luxury passenger cars, so this cost will decrease dramatically over time as the volume of production grows. Volvo estimates that it would cost about US$5,300 per vehicle to outfit it for platooning today. One can assume the costs will drastically reduce over time, but won’t go to zero. There should also be some kind of remuneration for the lead driver because he bears the burden of driving (and maybe the liability) while only getting some of the fuel economy benefits. While it may not be considered an actual financial hurdle, there are definitely entrepreneurial opportunities for a service that sets up platoons and manages the financial transactions.

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Thinking Highways
By Rick Sterrett May 13, 2014 15:44