Environment and Climate

Exhaust emissions

Since the start of the nineties, the introduction of the standard European exhaust emissions regulations has meant that vehicle emissions in the EU are measured on the basis of a standard driving cycle.

WLTP – Worldwide Harmonized Light Vehicles Test Procedure

Despite many objective benefits, the NEDC is increasingly attracting criticism, some of it justified, that it is no longer representative for the average driving style of a vehicle or driver. The member states which signed the 1998 treaty of the UNECE (including all the European countries as well as Japan, the USA, China, Russia and India) therefore decided to develop a new test procedure, the WLTP,  under the auspices of the UNECE. This should be properly representative of the driving style of a vehicle anywhere in the world. The automotive industry played a major role in supporting and advancing this initiative.

The new WLTP cycle (Worldwide Harmonized Light Vehicles Test Procedure) was developed on the basis of driving data gathered from around the world and covers driving situations from urban traffic to highways. In contrast to the NEDC, the WLTP test procedure is much more dynamic since it has many more acceleration and braking cycles than its predecessor. In addition to the actual driving profile, the measurement procedure has also been standardized globally and tailored to current automotive engineering. Questions relating to the temperature at which a vehicle is measured or the definition of the correct tire pressure are included in the standard of the WLTP.

New cycle WLTP

WLTP NEDC

Start temperature

Cold

Cold

Cycle time

30 min.

20 min.

Stationary time proportion

13 %

25 %

Cycle length

23.25 km

11 km

Speed

Average: 46.5 km/h – Maximum: 131 km/h

Average: 34 km/h – Maximum: 120 km/h

Drive power

Average: 7.5 kW – Maximum: 47 kW

Average: 4 kW – Maximum: 34 kW

Influence of optional equipment and air-conditioning (AC)

Optional equipment is taken into account for weight, aerodynamics and VES requirements (no-load current). No AC

Not considered at present

The aim of the new test procedure of the WLTP is to simulate reality as closely as possible, minimize variances and keep the cost of tests as low as possible. As with the NEDC, the measurement process should be reproducible and achieve conformity all over the world. A vehicle of the same type must produce the same test results anywhere in the world at any time if the measurement procedure is followed correctly. To ensure this, the test procedure must be able to determine the fuel consumption and emissions of a vehicle reliably and on a representative basis.

The development of the WLTP was divided into two phases. The first phase included the cycle and the test procedure and therefore provided the basis for the application of the WLTP in legislation. Phase 2 will then harmonize additional points such as on-board diagnostics, consideration of additional consumers and in-use topics.

Phase 1 of the WLTP development was completed in principle in March 2014 in a first phase, referred to as phase 1a. The completion of this phase saw the cycle and the procedure being practically applicable for conventional vehicles. The outstanding points from Phase 1 will be dealt with by the end of 2015. These include the correct treatment of plug-in hybrid vehicles and fuel cell vehicles, but also the continued revision of marginal conditions for tests. Only after the so-called phase 1b has been completed can the WLTP also become law in Europe.

Sensitive CO2 monitoring in Europe will initially remain the basis of the NEDC until the planned introduction of the WLTP starting in September 2017. This is why vehicles that are newly certified using the WLTP must initially be regarded as having being certified using the NEDC. The EU Commission is working on a correlation of NEDC and WLTP for this purpose. This correlation work is expected to be completed by mid-2015. The correlation only covers conventional vehicles and does not consider alternative powertrain types such as plug-in hybrids. Together with the industry, the EU has agreed on the required accuracy of this correlation work with a maximum individual error of 3 g/km. This high accuracy level is necessary because for every gram by which the CO2 target is missed, a fine of 95 euros per vehicle is imposed. The introduction of the WLTP must therefore not result in CO2 legislation becoming more stringent. The EU Commission is currently planning the conversion of CO2 monitoring to the WLTP. Individual CO2 target values for the NEDC for each manufacturer will be converted to the WLTP for this purpose. Starting from 2020, the EU Commission has stated its intention to monitor CO2 target achievement exclusively on the basis of WLTP monitoring and the manufacturers’ WLTP target values.

The VDA has major reservations about this early conversion of CO2 monitoring to the WLTP since the achievement of the targets in the WLTP cycle requires different engineering measures from those required for the NEDC. This situation will in fact result in the CO2 targets becoming more stringent, which would be illegal. The VDA therefore demands that the monitoring is not converted to the WLTP until after the NEDC targets have been achieved. Regardless of this, with the help of the correlation tool the WLTP can be used immediately after the introduction of the procedure to obtain the important consumption information. The VDA has prepared concrete proposals to this end.

Dr. Jakob Seiler Consultant

Tel: +49-30-897842-285 Fax: +49-30-897842-606
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