Friday 18 September 2020

Autonomous driving green credentials questioned

The amount of power required to run autonomous driving systems in future vehicles may well mean that the technology is unviable, according to a study jointly published by automotive environmental researchers Emissions Analytics and the Netherlands Vehicle Authority.

Various organisations, including the European Union and some vehicle manufacturers, have claimed that autonomous driving will make transport safer, cleaner and cheaper. These advantages will come from smoother driving and better coordination with traffic signals, it is suggested.

However, postulated savings can fail to take account of the energy required to run the powerful technology required, the report suggests.

A Level 5 automated vehicle will require a multitude of ECUs, plus camera, lidar, and radar systems: typically more than 20 power-hungry components, demanding around 200 W of electrical power per vehicle. Calculating the carbon footprint of the extra energy required from the current generation ‘mix’ in the Netherlands, this gives an electric car CO2 emissions from running the autonomous systems alone of 2.7 g/km. A fossil-fuelled car would be even worse, with an increased output of 5.3 g/km.

Yet more significant is the power required to process the data gathered by the various systems. Volvo suggests that “a few gigabytes of data” are generated every second that an autonomous vehicle is driven. Other sources suggest less than this, but the report says that even if just 0.4 GB is generated per second and this takes 0.1 kW of electricity to process, then this consumes sufficient energy to produce a ‘footprint’ of 1,950 g/km. The current average tailpipe CO2 output of a car in the Netherlands is just 121 g/km, and the EU is targeting an output of just 95 g/km, with car manufacturers facing fines of €95 per g/km over this.

If these fines were applied to automated vehicles, then the cost of automation would increase by €185,000 per vehicle.

There would also be an impact on the range of electrical vehicles, the report says; if 25 per cent of the data processing occurs on the vehicle, and the rest ‘in the cloud’, then the range of the average European electric car would be reduced to just 160 km. A vehicle with a 100 kW/h battery and 400 km range could travel just 70 km if autonomous driving systems were activated.

“This would clearly render automation unviable from both an emissions and cost point of view,” the report says. Even if all electricity was zero-carbon, some vehicles would lack the power to run the autonomous system and move simultaneously. And increasing demands for data security and vehicle safety could well see power demands increase.

“As a first step, it would be helpful to move beyond a narrative that uses ‘autonomous’ and ‘low emission’ as almost interchangeably good things. They are not. They more likely trade off against one another,” the report suggests.

The report speculates that the situation could be alleviated by new designs of computer chip with lower power consumption, or by limiting autonomous driving to certain areas and/or situations.

It further warns that, if successful, automation of private vehicles could have the unintended consequence of attracting users from public transport, making congestion and air quality worse.

“In short, the prospect offered by autonomous vehicles has been asserted by many to be ‘cleaner’, and this generally has been believed without in-depth scrutiny. As with tailpipe emissions, and as with battery electric vehicles, the message must be that independent, real-world data is vital to inform the debate and policy formation, to ensure that consumers and the market are not led down another avenue that in practice makes air quality or carbon emissions worse, often fertilised by large amounts of taxpayer money,” the report concludes.

The report can be downloaded at:

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