Transport makes up almost half our energy-related emissions in Aotearoa New Zealand. Choosing to walk or cycle, using public transport, or switching to electric vehicles are some of the ways we can reduce our transport emissions.

But if you do need to use a petrol or diesel car, another way to have an impact is to get in the habit of switching off your engine when your vehicle isn't moving — something known as engine idling. Engine idling is more common than people realise — and with petrol and diesel prices rising quickly, it's a great way to save money on fuel.

Idling for more than 10 seconds burns fuel inefficiently, leading to totally unnecessary emissions.

The problem with idle engines

Idling isn't good for several reasons, apart from damaging the environment. It can impact your vehicle's useful life, your health, and the health of the other motorists and pedestrians inhaling your fumes.

The emissions and fumes from idling engines have been linked to major health concerns including eye, throat, and bronchial irritation, nausea, coughs, allergies, increased risk for cardiac events, decreased lung function, and even cancer. For people with pre-existing heart disease, asthma or other lung problems, car emissions can be a major contributor to symptoms.

Children are particularly vulnerable because their respiratory systems are still developing, which makes idling a real issue around schools. Think about all the cars outside schools across the country that idle unnecessarily every day, creating pollution hotspots that are damaging to children's health.

Where we idle

We leave our engines running for many reasons — to keep the air con on, because we're distracted, or out of a sense that we've 'got to keep moving'.

Some of the most common situations for engine idling include:

  • waiting to pick up kids after school
  • waiting to meet someone
  • having a quick snack in the car
  • taking a phone call at the side of the road
  • keeping children and pets either cool or warm.

Cutting costs and emissions

Switching off your engine can lower your fuel costs. The amount of fuel a vehicle uses while idling ranges from between 0.75L/hour to 1.9L/hour for passenger vehicles1. At a petrol cost of $3/L for Unleaded 91, that works out to be between $2.25 and $5.70. To give context at a wider scale, the Argonne National Laboratory reports that in the U.S. alone, engine idling wastes more than $20 billion in fuel each year2 — that's around NZD $29 billion.

A recent Transport Energy/Emission Research report3 from Australia found that passenger vehicles are likely idle more than 20 per cent of their drive time. The report found that engine idling contributes up to 8 per cent of total carbon dioxide emissions over the journey, depending on the vehicle type. To put that into perspective, removing idling from the journey would be like removing up to 320,000 cars from New Zealand roads.

A lot of newer vehicles have a start-stop system that switches off a car's engine when the vehicle is stopped. According to the AA4 this technology delivers between 5 and 10 per cent lower emissions and also leads to a similar improvement in fuel economy.

The myth that switching your engine off and then turning it back on is bad for your vehicle or uses more fuel isn't true. It may have an impact on your battery but it is minimal and no reason not to switch off.

If you idle for 10 seconds or more, then turning off your engine and turning it back on does not burn more fuel than idling1. So stick to the 10-second rule. If you're idling for more than 10 seconds, turn off your engine.

Breaking the habit

We don’t need to have our engines running in most situations. We can fix the temperature issue by opening the windows, parking in the shade, or bringing an extra layer. If you’re parked and using an in-built system for taking calls, switch to using your handset instead. If you’re waiting to meet someone, you could wait outside, go in early and enjoy the air-con indoors, or take a quick walk around the block.

If you need to do the school run, switch off your engine unless you really can’t avoid it – and encourage others to do the same. To cut down on the number of cars idling outside your school, think about carpooling with your neighbours. Or better yet, join or start a walking school bus.

If your vehicle doesn’t have a start-stop system, try and get in the habit of switching off your engine whenever you’re stalled. If you’re frustrated by traffic, use it as a trigger to switch off your engine. Who knows, switching off your engine might actually reduce your stress levels too.

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