ICCT report shows discrepancies between type-approval and 'real-world' fuel consumption and CO2 values in 2001-2011 European passenger cars
Sun 15 April 2012
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A study by the International Council on Clean Transport (ICCT) based on analysis of data from more than 28,000 users has found that the gap between type-approval and 'real world' fuel consumption/CO2 values increased from about 8% in 2001 to 21% today, with a particularly strong increase since 2007. If correct, the results suggest that the rapid improvement in average new car fuel emissions produced by test data may not be fully realised in 'real world' driving conditions.
The ICCT paper compares fuel consumption / CO2 values of passenger cars from different sources and aims at quantifying the discrepancy between laboratory type-approval values and real-world values, including a retrospective analysis for the years 2001-2011 to determine if the gap between the two datasets has increased over time. Potential explanations for the discrepancies found are discussed and possible practical solutions for the future are outlined.
The results of the study are based on the analysis of more than 28,000 user entries of the German fuel consumption database spritmonitor.de and more than 1,200 vehicle models tested by Europe’s largest automobile club ADAC.
The ICCT report says that the potential reasons for the increased discrepancy between test and real world emissions include:
(i) increasing use of existing tolerances and loopholes in the determination of road load, vehicle weight, laboratory test temperatures, and transmission shifting schedules for type-approval;
(ii) inability of the current test cycle, the NEDC, to represent real-world driving conditions; and
(iii) increasing market share of vehicles equipped with air conditioning systems. In order to eliminate existing discrepancies as much as possible and to ensure that future improvements in vehicle technology result in real-world reductions of CO2 and fuel consumption, a number of changes to the existing test cycle, test procedure and compliance testing are recommended.
NB The discrepancy between test-cycle and 'real world' emissions will be the subject of a dedicated session at the LowCVP's Conference on May 10. Speakers include Peter Mock of the ICCT and Chas Hallett, Editor-in-Chief, WhatCar? which has just launched its 'True MPG' initiative. (See related story.) For more about the LowCVP Conference, click here.
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