Worldwide Harmonised Light Vehicles Test Procedure
The Worldwide Harmonised Light vehicles Test Procedure is a global driving cycle standard for determining the levels of pollutants, CO2 emission standards and fuel consumption of conventional internal combustion engine and hybrid automobiles, as well as the all-electric range of plug-in electric vehicles.
The WLTP was adopted by the Inland Transport Committee of the United Nations Economic Commission for Europe as Addenda No. 15 to the Global Registry defined by the 1998 Agreement. The standard is accepted by China, Japan, the United States and the European Union, among others. It aims to replace the previous and regional New European Driving Cycle as the new European vehicle homologation procedure. Its final version was released in 2015.
One of the main goals of the WLTP is to better match the laboratory estimates of fuel consumption and emissions with the measures of an on-road driving condition. Since CO2 targets are becoming more and more important for the economic performance of vehicle manufacturers all over the world, WLTP also aims to harmonize test procedures on an international level, and set up an equal playing field in the global market. Besides EU countries, the WLTP is also the standard fuel economy and emission test for India, South Korea and Japan. In addition, the WLTP ties in with Regulation 2009/443 to verify that a manufacturer’s new sales-weighted fleet does not emit more CO2 on average than the target set by the European Union, which is currently set at 95 g of CO2-eq per kilometer for 2021.
History
The regulation took into account various national cycles such as World-wide Heavy-Duty Certification procedure and World-wide Motorcycle Test Cycle. It also took into consideration the 1958 Agreement and the 1998 Agreement, those of Japan and the United States Environmental Protection Agency Standard Part 1066.From NEDC to WLTP standard
From 1 September 2019 all light duty vehicles that are to be registered in EU countries must comply with the WLTP standards. The WLTP replaces the old NEDC as the European homologation lab-bench procedure, which was established in the 1980s to simulate urban driving conditions for a passenger car. In 1992 the NEDC was updated to also include a non-urban path, and finally in 1997 CO2 emission figures were added, too. Nowadays, the NEDC cycle has become outdated since it is not representative of modern driving styles, as the distances and road varieties a mean car has to face have changed since the test's design. The structure of the NEDC is characterized by an average speed of 34 km/h, smooth accelerations, few and prolonged stops and a top speed of 120 km/h.The new standard has been designed to be more representative of real and modern driving conditions. To pursue this goal, the WLTP is 10 minutes longer than the NEDC, its velocity profile is more dynamic, consisting of quicker accelerations followed by short brakes. Moreover, the average and the maximum velocities have been increased to 46.5 km/h and 131.3 km/h respectively. The distance covered is 23.25 km.
The key differences between the old NEDC and new WLTP test are that WLTP:
- has higher average and maximum speeds
- includes a wider range of driving conditions
- simulates a longer distance
- has higher average and maximum drive power
- looks at steeper accelerations and decelerations
- tests optional equipment separately
| Car | NEDC autonomy | WLTP autonomy | Decrease |
| Renault Zoé | 400 km | 300 km | 25% |
| BMW i3 | 300 km | 245 km | 18% |
| Hyundai Kona electric 64 kWh | 546 km | 482 km | 12% |
Test procedure
The test procedure provides strict guidance regarding conditions of dynamometer tests and road load, gear shifting, total car weight, fuel quality, ambient temperature, and tyre selection and pressure.Three different WLTC test cycles are applied, depending on vehicle class defined by power/weight ratio PWr in W/kg :
- Class 1 – low power vehicles with PWr ≤ 22;
- Class 2 – vehicles with 22 < PWr ≤ 34;
- Class 3 – high-power vehicles with PWr > 34;
In each class, there are several driving tests designed to represent real world vehicle operation on urban and extra-urban roads, motorways, and freeways. The duration of each part is fixed between classes, however the acceleration and speed curves are shaped differently. The sequence of tests is further restricted by maximum vehicle speed Vmax.
To ensure comparability for all vehicles, thus guaranteeing a fair comparison between different car manufacturers, the WLTP tests are performed in the laboratory under clear and repeatable conditions. The protocol states that:
- The velocity profile that the tested vehicle must repeat
- Laboratory instrumentation parameters, such as the calibration of dynamometers, gas analyzers, anemometers, speedometers or the rolling resistance of the test bench
- Environmental conditions, such as room temperature, air density, wind
- Fuel type: gasoline, diesel, LPG, natural gas, electricity, etc.
- Fuel quality and its chemical properties
- The tolerances under which the measures are valid
- The set-up process for vehicles ahead of the test.
The procedure does not indicate fixed gear shift point, unlike the NEDC, letting each vehicle use its optimal shift points. In fact, these points depend on vehicle unique parameters as weight, torque map, specific power and engine speed.
During the WLTP the impact of the model’s optional equipment is also considered. In this way the tests reflect better the emissions of individual cars, and not just the one with the standard equipment. In fact, for a same car, the homologation procedure needs two measures: one for the standard equipment and the other one for the fully equipped model. This takes into account the effect on vehicle’s aerodynamics, rolling resistance and change in mass due to the additional features.
WLTC driving cycles
The new WLTP procedure relies on the new driving cycles to measure mean fuel consumption, CO2 emissions as well as emissions of pollutants by passenger cars and light commercial vehicles.Class 3
The WLTP is divided into 4 different sub-parts, each one with a different maximum speed:- Low, up to 56.5 km/h
- Medium, up to 76.6 km/h
- High, up to 97.4 km/h
- Extra-high, up to 131.3 km/h.
| Low | Medium | High | Extra high | Total | |
| Duration, s | 589 | 433 | 455 | 323 | 1800 |
| Stop duration, s | 150 | 49 | 31 | 8 | 235 |
| Distance, m | 3095 | 4756 | 7162 | 8254 | 23266 |
| % of stops | 26.5% | 11.1% | 6.8% | 2.2% | 13.4% |
| Maximum speed, km/h | 56.5 | 76.6 | 97.4 | 131.3 | |
| Average speed without stops, km/h | 25.3 | 44.5 | 60.7 | 94.0 | 53.5 |
| Average speed with stops, km/h | 18.9 | 39.4 | 56.5 | 91.7 | 46.5 |
| Minimum acceleration, m/s2 | -1.5 | -1.5 | -1.5 | -1.44 | |
| Maximum acceleration, m/s2 | 1.611 | 1.611 | 1.666 | 1.055 |
Class 2
The Class 2 test cycle has three parts for low, medium, and high speed; if Vmax < 90 km/h, the high-speed part is replaced with low-speed part.| Low | Medium | High | Total | |
| Duration, s | 589 | 433 | 455 | 1477 |
| Stop duration, s | 155 | 48 | 30 | 233 |
| Distance, m | 3132 | 4712 | 6820 | 14664 |
| % of stops | 26.3% | 11.1% | 6.6% | 15.8% |
| Maximum speed, km/h | 51.4 | 74.7 | 85.2 | |
| Average speed without stops, km/h | 26.0 | 44.1 | 57.8 | 42.4 |
| Average speed with stops, km/h | 19.1 | 39.2 | 54.0 | 35.7 |
| Minimum acceleration, m/s2 | -1.1 | -1.0 | -1.1 | |
| Maximum acceleration, m/s2 | 0.9 | 1.0 | 0.8 |
Class 1
The Class 1 test cycle has low and medium-speed parts, performed in a sequence low–medium–low; if Vmax < 70 km/h, the medium-speed part is replaced with low-speed part.| Low | Medium | Total | |
| Duration, s | 589 | 433 | 1022 |
| Stop duration, s | 155 | 48 | 203 |
| Distance, m | 3324 | 4767 | 8091 |
| % of stops | 26.3% | 11.1% | 19.9% |
| Maximum speed, km/h | 49.1 | 64.4 | |
| Average speed without stops, km/h | 27.6 | 44.6 | 35.6 |
| Average speed with stops, km/h | 20.3 | 39.6 | 28.5 |
| Minimum acceleration, m/s2 | -1.0 | -0.6 | |
| Maximum acceleration,m/s2 | 0.8 | 0.6 |