How automated driving saves coffee. And energy.
In dense traffic, individuals’ bad driving habits often make things worse for all road users. Research now shows that a single automated vehicle can greatly improve the traffic flow and reduce gasoline consumption.
It is a characteristic of human nature that, whatever we desire, we are likely to foil our own objectives. This is particularly true in road traffic. While a single car affords individual freedom of movement in a brisk and comfortable manner, the rapidly growing number of cars makes road travel highly inefficient. It also leads to dramatic consequences not just for our environment, but also for people’s individual health and well-being.
To a large degree, this is of our own making. Some 60% of traffic jams on German roads are caused by over-burdened streets and bad driving habits, as research by Michael Schreckenberg, a professor of physics of transport and traffic, indicates. “Taking the human element out of driving and enabling vehicles to communicate independently can make road traffic significantly more efficient,” Schreckenberg said in an interview with 2025AD.com.
This is where automated driving (AD) comes in. Vehicle-to-vehicle (V2V) communication, which is an important tool in fully automated traffic, allows cars, trucks and buses to share data such as speed and position in real time. A connected vehicle can adjust its speed to what happens several cars ahead and thereby smooths the traffic flow. This also shows how AD can deliver on its promise to reduce harmful emissions as well as energy consumption.
A pace car for commuters’ daily race
Tests on public roads by University of Michigan researchers have now shown that a single automated and connected car can make the traffic flow better for all by avoiding phantom traffic jams. When the researchers drove around in a mixed human and machine driver convoy, human drivers slammed on the brakes as hard as usual. With advance knowledge of events happening beyond line of sight, the connected car was able to smooth the braking process to the point where even the passengers’ coffee remained in its cups.
The research also showed that human-driven cars following the automated vehicle can save up to seven percent energy, thanks to the smoother speed profile, the university reported. “Automated cars utilizing V2V data will not only perform better, but they can also foster a friendlier environment where few safety hazards sneak into traffic and higher efficiency is possible for all cars on the road,” said Gabor Orosz, associate professor of mechanical engineering who led the research.
A similar experiment by University of Illinois researchers showed that if only one in 20 cars is partially automated, it can reduce the stop-and-go that often leads to traffic jams. Such cars could calm down the daily race of commuters, much like a pace car in the Formula One.
A giant laboratory
Such polishing is much needed. Close to 64 million cars were registered in Germany in early 2018 – up from barely 50 million vehicles in 2008. In the US, the latest figures available show that some 269 million vehicles were in operation in 2016 – significantly more than the 193 million in 1990. And the vehicle fleet in China is growing rapidly as well. The International Organization of Motor Vehicle Manufacturers counted six million new cars sold in the US and 18 million in Europe in 2017. Yet Chinese consumers bought a total of 25 million new passenger cars in the same year. While much of this is caused by issues outside the scope of automated driving such as population growth, increasing wealth and consumerism, automated driving can help mitigate the negative effects of such growth.
More than 100 years ago, the precursors of German autobahns were originally conceived to free the swift movement of newly invented automobiles from the slog of horse carriages. Today, they allow the formation of traffic jams in their purest form and are a giant laboratory for researchers like Schreckenberg.
Schreckenberg first examined the peculiarities of human traffic in the 1990s, drawing raised eyebrows from many colleagues who considered the field unworthy of a true physicist’s attention. Undeterred, Schreckenberg and Kai Nagel, now a professor at Technical University Berlin, delved into the topic and developed the Schreckenberg-Nagel model.
What causes traffic jams?
It shows that velocity fluctuations cause traffic jams. As a faster car approaches a slower one, it is forced to brake. If the traffic is dense and the following car close enough, drivers brake even harder to make up for a second lost (36 meters at 130km/h) due to average reaction time. If this happens often enough, it will cause a traffic jam out of nothing. This becomes obvious when drivers are asked to move in a circle. If the experiment is continued long enough, traffic jams will form – without any obstacle other than human driving behavior.
When the way forward is blocked, humans tend to react in panic. They apply more pressure to the individuals and vehicles ahead of them, leading drivers to closely follow the car in front or frequently change lanes. This is not a new phenomenon. “A jostling crowd of pedestrians at a bottleneck significantly reduces the flow rate and eventually creates a traffic jam,” Schreckenberg wrote in 2007.
When interviewed for 2025AD.com, he adds: “In any queue, humans almost always perceive the other line to be faster, because we tend to remember people and cars that pass us more than those we leave behind. This causes many drivers to often change lanes when traffic is slow.” However, this only worsens the situation for all. As vehicles squeeze into what little space remains between two cars, they force the rear vehicle to slow, causing another slight ripple in the traffic flow.
I know you don’t like jamming, too
Regularly spending time in congested traffic makes us truly miserable. It creates additional social and private costs, causes stress and can lead to medical issues such as raised blood pressure, musculoskeletal disorders, anxiety and others. And commuters often report a lower level of life satisfaction.
Economic theory assumes this would be compensated for by lower housing costs or higher paid jobs for those who bear these costs. However, this is not the case as a study by Alois Stutzer and Bruno Frey showed. Assessing people’s subjective well-being between 1985 and 2003 based on the German Socio-economic Panel Study, the researchers found that the income of those who commute would have to be 35% – or 470 euros – higher than it actually was to compensate for the German average commute time of 22 minutes. While Frey has since been chided by fellow academics for quoting himself without stating it (“self-plagiarism”), the negative impact of commuting has been confirmed by others. And still, Germans spend almost 60 hours per person per year sitting in traffic jams.
Yet automated driving is no panacea. Schreckenberg expects a long and bumpy transition period during which driverless cars mingle with traditionally guided vehicles. “The key question is whether automated driving will become compulsory, but I don’t see that coming.”
More complex decisions
A recent study by the International Transport Forum also sounds a note of caution. The authors point out that “claims of more than 90% reduction in road traffic deaths resulting from automation” are untested. While “it seems likely that the number of road casualties will decrease with automation,” more crashes may occur, particularly when drivers assume responsibility in emergency situations. “A shared responsibility for driving may not render decision making simpler, but more complex,” the study authors write.
The OECD report therefore advises to reinforce the Safe System approach, carefully assess handover situations between humans and machines and communicate vehicle capabilities clearly, an issue this website highlighted in the context of Tesla’s so-called “autopilot”.
It will likely take years before automated technology is common. In the meantime, we may find some consolation in the fact that even a few highly innovative vehicles will make our lives easier.