In laboratory tests, a car is put on a chassis dynamometer – a ‘rolling road’ – and is driven through a prescribed test cycle, while the vehicle’s driving resistance is being simulated by the test bench. During the test, exhaust gases are collected and/or energy consumption is measured. These gases are analysed at the end of the drive-cycle to determine the amount of pollutant emissions, particulate matter and greenhouse gases the car emitted during the cycle.
At the core of Green NCAP’s lab tests is the World-harmonised Light-vehicles Test Cycle (WLTC), introduced in 2017 as a global test procedure developed on the basis of global real-driving data and aiming at representativeness of everyday driving. The WLTC replaced the old NEDC test cycle (New European Driving Cycle) which had been in use for some 40 years previously. The WLTC driving cycle is divided into four parts (low, medium, high, extra high), which address different types of use, with a wide variation of driving behaviour and driving situations. Each part represents different driving phases like city or urban driving with a variation of vehicle speeds and different stop times, accelerations and braking phases.
The WLTC+ Cold test done in previous years yielded results that were in close agreement with the legislative type-approval tests that all cars have to pass. Accordingly, from 2025, the emissions and consumption results of the type-approval tests according to the World-harmonised Light-vehicles Test Procedure (WLTP) are used as part of the assessment, without the need to repeat the test.
Green NCAP’s own laboratory tests are based on the WLTC test procedure but with more realistic and extended boundary conditions, which is signalised by the “+” suffix in “WLTC+”.
Green NCAP evaluates the robustness of the vehicle’s exhaust after-treatment system and energy saving technologies. This ‘robustness’ checks that the emissions-control systems work effectively over a broad range of conditions and not just in one prescribed test. To evaluate this, the tests are performed with different ambient temperatures and starting conditions like cold or warm engine start. The WLTC+ Cold Ambient Tests (CAT or Winter cold start and Winter warm start tests) are performed at -7°C.
The main purpose is to have realistic and comparable results from different cars and propulsion systems
To evaluate the robustness of the exhaust after-treatment system and to obtain the fuel-energy demand at high engine loads, and vehicle speed a Highway test-cycle (BAB130) is also performed. This test cycle has a maximum speed of 130 km/h and includes several hard accelerations from 80 km/h to 130 km/h.
In summary, five different lab tests are rated:
Legal test – WLTP official type approval results
- WLTP – The Worldwide Harmonised Light Vehicles Test Procedure (WLTP) is a global driving cycle standard for determining the levels of pollutants, CO2 emission standards and fuel consumption of road vehicles. As of 2025, Green NCAP uses the officially declared emissions and consumption WLTP results of tested vehicles as part of the rating.
- Warm weather – WLTC+ warm engine start at 23°C ambient temperature
- Highway – BAB130 highway test-cycle at 23°C
- Winter cold start – WLTC+ CAT (Cold Ambient Test) cold vehicle start at -7°C
- Winter warm start – WLTC+ CAT (Cold Ambient Test) warm vehicle start at -7°C
As of 2025, the WLTC+ CAT test is performed twice: once from a cold start i.e. where the car and its powertrain are at -7°C at the beginning of the test; and again from a warm start i.e. the ambient temperature of the test laboratory is still -7°C, but the car has been previously driven and is warm. The results can be used to indicate the car’s performance during a cold winter start and in prolonged winer driving.
Plug-in hybrid electric vehicles (PHEVs) are subjected to all of these laboratory tests in charge-sustaining mode (i.e. when running mainly using the combustion engine). In charge-depleting mode (i.e. when the test starts with a fully charged battery), only the WLTC+ cold test is used.
During all cycles, the pollutants (NMHC, CH4, CO, NOx, NH3 and PN 10) and CO2 emissions are measured as well as the fuel/energy consumption values.
For more detailed information, see Test Procedures.
The programmes reveals the vehicle’s behaviour in a range of scenarios – from preconditioned light trips to challenging full power or freezingly cold tests.
The main purpose of the lab tests is to have the most realistic and comparable results from different cars and propulsion systems in terms of their emissions and fuel economy/energy efficiency. The test conditions, the vehicle set-up and the execution of the tests are standardised and clearly defined. This is important for a fair comparison and a high-quality assessment and evaluation of cars.