What Are Road Trains or Platoons?

The term “road train” or “road platoon” is used to describe groups of vehicles that drive along in a line, one after the other, in a “follow the leader” fashion. The idea is to have the lead vehicle controlling the pace of the platoon with the¬†vehicles behind following along at set distances, mimicking the pace vehicle’s speed and movement. It is most suitable for highway or freeway driving scenarios over some distance. A commute of 15 miles on a freeway, for example, could be accomplished via road train technology whereas a drive through town over three miles would not see much benefit.

Because the vehicles that are following are “tied” to the lead vehicle in terms of speed and braking, the train of vehicles can be much more closely bunched together than would otherwise be safe. This has the advantage of both adding more aerodynamics to the individual vehicles in the train as well as to the group as a whole. This, overall, improves fuel economy on the road.¬†It frees up driving so that a driver and passengers can do things other than pay attention to the traffic on their commute.

The idea of road platoons was first proposed in the 1960s as part of a U.S. Federal Highway Administration funding grant to find new ways of solving growing congestion problems. Most research, however, has been conducted within the past decade in the United States, Europe, and Asia.

How It Works

Platooning is accomplished through vehicle-to-vehicle communications and some specialized sensors and computers. It’s possible to retrofit existing vehicles to make their road platoon-ready as well as manufacture new vehicles with the capability built-in. Most current platoon scenarios have the lead vehicle manned by a professional driver with extra training or experience. In the future, this could be an endorsement on a driver’s license or platoons could follow public transportation vehicles such as buses.

Vehicles also communicate with the infrastructure of the roadway itself. There are several schemes for this, including transponders mounted alongside or over the highway, special lanes made specifically for road trains with embedded strips or spikes that the cars can “read,” and road signs that allow and RFID transponder or other means of “reading” the sign. Or any combination of these things.

These combinations of data allow the vehicle to follow closely behind a leader and to communicate with the other vehicles in the platoon, giving near-instantaneous feedback and information on upcoming hazards, speed changes, distances, and more. They also allow the vehicle to know when to know when it should break away from the train to exit and to alert the other vehicles in the platoon as to its intentions to do so.

Current Research

Most of the current research happening in road platoons is centered on allowing autonomous vehicles and semi-autonomous vehicles to “link” together without much change to the current highway infrastructure. The Federal Highway Administration conducts and organizes research and testing through its Automated Highway System Consortium (AHS). Participants include BMW, Daimler (Mercedes-Benz), Toyota, Volkswagen, and Volvo.

In Europe, the Safe Road Trains for the Environment (SARTRE) project is funded through the European Commission with similar aims. Thus far, most of the on-road research for platooning has been SARTRE-led with Volvo Car and Volvo Trucks being at the forefront.