Could autonomy increase emissions?

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A joint newsletter authored by representatives of Emissions Analytics, a global independent emissions testing agency, and the Netherlands Vehicle Authority (RDW), questions whether autonomous vehicles will in fact contribute to a reduction in carbon emissions.

The letter suggests that, though on initial appearances, autonomous vehicles could improve emissions alongside road safety, a lack of consideration of factors such as the energy demands of internal and external devices needed to achieve autonomy could change this.

After reappraising a study undertaken in 2017 by the Centre for Transport Studies at Imperial College London called Optimised Vehicle Autonomy for Ride and Emissions (OVARE), which Emissions Analytics was involved in, it was found the omission of these factors could significantly change the result of the modeling that was conducted.

The OVARE project involved creating a traffic micro-simulation using the PTV-VISSIM software, coupled with instantaneous emissions factors derived from data from Emissions Analytics collected using Portable Emissions Measurement Systems (PEMS). Pollutants included were carbon dioxide (CO2), carbon monoxide (CO) and nitrogen oxides (NOx), together with fuel consumption derived using the carbon balance method.

The findings showed a marked reduction in emissions, around 18%, however, once energy consumption related to autonomy is accounted for, this may not be a valid conclusion.

The authors suggest that the average energy consumption over a year is 88kWh. This is based on an average energy consumption for autonomous hardware of 200W (not including data processing) and data from the Netherlands – as an advanced European economy – giving the average number of driving hours per passenger car per year as 440 hours. Data processing would add up to an (approximate) 7.1kWh. The exact figure depends on whether the processing takes place on or off car.

As the letter summarises, the efficiencies gained from autonomy could well be canceled out by the greater power demands of supporting systems.

The authors said, “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 full text of the letter can be found here.

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