Hybrids’ zero-emissions benefits backed by new Irish study

UCD researchers find Toyota Prius cars spend majority of journey time in ZEV mode

A study by academics at UCD has found that new Toyota Prius hybrid cars tested over 2,000km through a variety of commutes in Ireland spent 62 per cent of the time in zero emissions mode.

The seven academics each tested a Prius over a week last November, while commuting to UCD from a variety of locations and during normal family driving. Over 157 individual trips, the total distances completed by each driver ranged from 119.7km for a Smithfield commuter to 644.2km for a driver commuting from Drogheda, Co Louth.

The study by ConsultUCD, commissioned by Toyota Ireland, found thatthe hybrid Prius managed to remain in zero emissions mode for more than 50 per cent of the time and over 30 per cent of the distance covered, even in the long-distance commutes.

The data was collected using the car’s telemetrics system and an Android app that monitors electric vehicle activation patterns. The trips involved journeys using motorways, rural roads and city driving. Unlike a similar test carried out in Rome in 2016, no restrictions or driving guidelines were given to the drivers and the various driving routes taken by the test drivers were not agreed beforehand.


During the week in November, the cars were used for commuting, school runs and incidental daily and weekend journeys.

One of the criticisms of hybrid technology is that its benefits are only really achieved in low-speed city driving. It has also been suggested that the real benefits only accrue to drivers who actively attempt to maximise battery mode driving.

However, the study found that even the commuters travelling from Drogheda, Aughrim and Wicklow town to UCD spent 56 per cent of their time in zero emissions mode over the respective 644km, 452km and 293km driven over the course of the week's testing.

As for city driving, the commuting academic from Smithfield was in zero emissions mode on average 76 per cent of the time and for 57 per cent of the distance, while drivers from Dundrum and Blackrock were in zero emissions for two-thirds (64-67 per cent) of the time.

Zero emissions mode describes the time the internal combustion engine is not running and the vehicle is therefore emitting no pollutants. The longer the car is in ZEV mode the more significant the air quality benefits for other road users.

Fuel consumption

The study also revealed that, on average, fuel consumption for the Prius was 4.92 litres per 100km (57mpg) and average CO2 emissions were 114.2 grammes per kilometre. The three drivers with the longest commutes had the best fuel economy, averaging almost 60mpg, a fact that clearly demonstrates the merits of hybrid cars for long-distance driving.

The Prius models involved were Luxury grade with 17-inch alloys. According to the study, it represents more than 90 per cent of Prius models sold in Ireland. November was chosen for the study so that warmer weather would not unduly benefit the car’s battery pack.

UCD's Prof David Timoney said: "Highlights of the study include a high percentage of zero-emissions driving recorded across a wide range of conditions, which may provide environmental benefits for the wider population. Also noteworthy is the close agreement of the measured fuel economy with the official worldwide harmonised light vehicle test procedure figure."

According to Toyota corporate affairs director Mark Teevan: "This is the first study of this type carried out in Ireland, and we anticipate its results would be replicated across the country.

“The study confirms that Toyota Prius hybrids spend the majority of their time in zero emissions mode and provides vital learnings for Ireland as the country sets about decarbonising the Irish car fleet,” he said.

Michael McAleer

Michael McAleer

Michael McAleer is Motoring Editor, Innovation Editor and an Assistant Business Editor at The Irish Times