A simple driving trick could make a big dent in cars’ carbon emissions

You may be guilty of accelerating up to intersections and slamming the brakes at a red light – this common habit can generate significant carbon emissions each year. But programming modern cars to glide up to intersections instead could significantly reduce annual emissions.

An AI-powered model suggests that if every single gas or diesel-powered vehicle in the US consistently followed certain eco-driving practices, they could cut the country’s yearly carbon emissions by between 62 million and 123 million tonnes.

But even if just 10 per cent of US vehicles adopt these eco-driving behaviours, they could still achieve up to half of the possible emissions reductions. This makes sense given how eco-driving vehicles can influence the speed and braking behaviour of other vehicles following behind them, says Vindula Jayawardana at the Massachusetts Institute of Technology.

“That means we don’t necessarily need to wait long for the eco-driving adoption to get really high to get the benefits,” says Jayawardana.

To estimate the potential emissions reductions from various forms of eco-driving – including gliding towards stops and limiting idling time at intersections – Jayawardana and his colleagues modelled vehicle behaviour at more than 6000 intersections in three major US cities: San Francisco, Los Angeles and Atlanta, Georgia. Those cities were chosen to represent the country’s diverse range of geographies and factors that can influence driving.

The model accounted for varying traffic and environmental conditions, such as lane configurations and weather, and ultimately simulated nearly 1 million different scenarios. The researchers then trained artificial intelligence agents through trial and error to figure out what would most significantly reduce carbon emissions and travel time. They found that gliding towards intersections and limiting idling time while waiting at intersections was most effective.

If all drivers in these cities consistently followed these practices, possible emissions reductions at intersections varied from 11 to 22 per cent, depending on each city’s driving conditions. A city like Atlanta, which has relatively high speed limits and long approaches to intersections, can benefit more from eco-driving than, say, San Francisco.

The study’s main estimates of emissions reductions are based only on internal combustion engine vehicles and do not account for the growing presence of electric or hybrid vehicles. But Jayawardana says, “Even if the adoption of [electric vehicles] is 100 per cent, we can still benefit from eco-driving as long as the electric grid is not clean.”

In the future, traffic signal devices at intersections could also communicate with approaching vehicles to alert them to start slowing down, says Jayawardana. The study showed that nearly 70 per cent of emissions reduction benefits came from just 20 per cent of all the intersections, which suggests cities could focus on upgrading equipment at those locations.

Eco-driving can offer “small but significant potential energy savings benefits” while also smoothing out driving behaviour and reducing traffic jams, says Chris Hendrickson at Carnegie Mellon University in Pennsylvania. But he cautioned that more work is required to figure out the most effective forms of eco-driving and to standardise vehicle automation and connectivity systems.

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