This report primarily investigates the factors that affect fuel consumption and CO2 emissions which are not accounted for in the current type approval test and result in a shortfall between type approval and real-world fuel consumption or the corresponding CO2 emission values. A comprehensive literature review is carried out, in which we examine the available information and aim to provide qualitative and quantitative data. Where information is e insufficient, we point out the gap in knowledge. In addition, we have examined by means of simulation the significance of several factors that may change during every-day operation and may depend either on the driver or on external conditions.
Several factors were identified affecting the in-use fuel consumption and CO2 emissions resulting in a shortfall between the type approval and real-world values. These include the increased electrical power load (e.g. A/C, steering assist), aerodynamic alterations (roof box, aerofoils), ambient conditions (temperature, wind, rain and altitude), driving behavior (aggressive driving, driver training), vehicle condition (lubrication, tyre condition), increased vehicle mass (passengers, additional equipment), road conditions (road surface, traffic conditions). They are complemented by so-called "flexibilities" associated with the existing NEDC-based type approval procedure. The combined effect of the different factors affecting CO2 emissions,, although not fully cumulative, can result in shortfall values ranging between 25% and 35%, based on information collected, the calculations run and the assumptions adopted in this study. These figures are in line with other literature sources where shortfall ranges from 20% up to 50% compared to the official certification value are reported. The per-passenger CO2 performance significantly improves when the occupancy rate is considered, hence a separate analysis was performed to this end. It can be concluded that due to the increase complexity of modern vehicles, the increasing number of passenger comfort systems and the great variety of possible operating conditions, it is difficult to capture the real-world fuel consumption with an exhaustive accuracy. It is expected that the introduction of the new test protocol (WLTP) will be a step forward in closing this shortfall. A separate analysis on the expected WLTP impact on CO2 is presented. It cannot be overlooked that driver behavior is an important element and therefore additional measures, in particular proper driver training and information, can help to reduce the discrepancy observed by drivers between their own in-use CO2 emissions from passenger cars compared to the test results.
ZACHAROF Nikiforos Georgios;
FONTARAS Georgios;
CIUFFO Biagio;
TSIAKMAKIS Stefanos;
ANAGNOSTOPOULOS Konstantinos;
MAROTTA Alessandro;
PAVLOVIC Jelica;
CODREA Cosmin;
HODGSON Ian;
2016-11-17
Publications Office of the European Union
JRC100150
978-92-79-57593-8 (online),
978-92-79-57592-1 (print),
978-92-79-86465-0,
1831-9424 (online),
1018-5593 (print),
EUR 27819 EN,
OP LD-NA-27819-EN-N (online),
OP LD-NA-27819-EN-C (print),
OP LD-NA-27819-EN-E,
https://publications.jrc.ec.europa.eu/repository/handle/JRC100150,
10.2790/140640 (online),
10.2790/74318 (print),
10.2790/491445,
