The WLTP was adopted by the Inland Transport Committee of the United Nations Economic Commission for Europe (UNECE) as Addenda No. 15 to the Global Registry (Global Technical Regulations) defined by the 1998 Agreement.[2] The standard is accepted by China, Japan, the United States and the European Union, among others.[3] It aims to replace the previous and regional New European Driving Cycle (NEDC) as the 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.[4]
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 (EC) 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 95g of CO2 per kilometer for 2021.[5][6]
History
The regulation took into account various national cycles such as World-wide Heavy-Duty Certification procedure (WHDC) and World-wide Motorcycle Test Cycle (WMTC).[7] It also took into consideration the 1958 Agreement and the 1998 Agreement, those of Japan and the United States Environmental Protection Agency (US EPA) Standard Part 1066.[7]
From 1 September 2019 all light duty vehicles that are to be registered in EU countries (and also in Switzerland, Norway, Iceland and Turkey) must comply with the WLTP standards.[4] 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.[8] In 1992 the NEDC was updated to also include a non-urban path (characterized by medium to high speeds), and finally in 1997 CO2 emission figures were added, too.[9] Nowadays, the NEDC cycle has become outdated since it is not representative of modern driving styles, as the distances and road varieties a mean car has to face have changed since the test's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.[10][11] The structure of the NEDC is characterized by an average speed of 34km/h, smooth accelerations, few and prolonged stops and a top speed of 120km/h.[12]
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 (30 instead of 20 minutes), 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 46.5km/h and 131.3km/h respectively. The distance covered is 23.25km (more than double the 11 kilometers of the NEDC).[5]
The key differences between the old NEDC and new WLTP test are that WLTP:[4]
has higher average and maximum speeds
includes a wider range of driving conditions (urban, suburban, main road, highway)
simulates a longer distance
has higher average and maximum drive power
looks at steeper accelerations and decelerations
tests optional equipment separately
As the result, the performance of the car is decreased.
The test procedure provides strict guidance regarding conditions of dynamometer tests and road load (motion resistance), gear shifting, total car weight (by including optional equipment, cargo and passengers), fuel quality, ambient temperature, and tyre selection and pressure.
Most common cars nowadays have power-weight ratios of 40–100W/kg, so belong to class 3. Vans and buses can also belong to class 2.
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.[citation needed]
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:[6]
The velocity profile that the tested vehicle must repeat (indicating one speed value for each of the 1800 seconds)
The set-up process for vehicles ahead of the test.
The last two are stricter than in the NEDC protocol, since they were previously used by car manufacturers to their advantage to keep CO2 values (legally) as low as possible.[11]
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.[5]
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 (as it was for the NEDC cycle). 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.[5] This takes into account the effect on vehicle’s aerodynamics, rolling resistance and change in mass due to the additional features.[8]
WLTC driving cycles
The new WLTP procedure relies on the new driving cycles (WLTC – Worldwide harmonized Light-duty vehicles Test Cycles) to measure mean fuel consumption, CO2 emissions as well as emissions of pollutants by passenger cars and light commercial vehicles.[14]
Class 3
The WLTP is divided into 4 different sub-parts, each one with a different maximum speed:
Low, up to 56.5km/h
Medium, up to 76.6km/h
High, up to 97.4km/h
Extra-high, up to 131.3km/h.
These driving phases simulate urban, suburban, rural and highway scenarios respectively, with an equal division between urban and non-urban paths (52% and 48%).[5]
WLTC class 3 test cycle
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 < 90km/h, the high-speed part is replaced with low-speed part.
WLTC class 2 test cycle
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 < 70km/h, the medium-speed part is replaced with low-speed part.
WLTC class 1 test cycle
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
Transition timeline from NEDC to WLTP
The period of transition from NEDC to WLTP started in 2017 and ended in September 2019. Car manufacturers were required to obtain approval under both WLTP and NEDC for any new vehicle from 1 September 2017, while WLTP superseded NEDC from September 2018. From that date, measures of fuel consumption and CO2 emissions obtained under WLTP are the only ones with legal validity and are to be inserted in official documentations (the Certificate of Conformity).[5]
Since the structures of NEDC and WLTP are different, the values obtained can differ from one to the other even if the same car is being tested. As WLTP more closely reflects on-road going conditions, its laboratory measures of CO2 emissions are usually higher than the NEDC.[5] A vehicle’s performance does not change from one test from the other, simply the WLTP simulates a different, more dynamic path, reflecting in a higher mean value of pollutants. This fact is important, because the CO2 figure is used in many countries to determine the cost of Vehicle Excise Duty for new cars. Given the discrepancies between the two procedures the UNECE suggested the policymakers should consider this asymmetry during the transition process.[4] For example in the UK, during the period of transition from NEDC to WLTP, if the CO2 value was obtained under the latter, it had to be converted to a ‘NEDC equivalent’.[15]
Real drive emissions
AVL PEMS - attached on a passenger car
Along with the lab-based procedure, the UNECE introduced a test in real driving conditions for NOx and other particulate emissions, which are a major cause of air pollution. This procedure is called Real Drive Emissions test (RDE) and verifies that legislative caps for pollutants are not exceeded under real use. RDE does not substitute the laboratory test (the only one that holds a legal value), but it complements it. During RDE the vehicle is tested under various driving and external conditions that include different heights, temperatures, extra payload, uphill and downhill driving, slow roads, fast roads, etc.[4] In addition, the freestream air that the vehicle receives is not conditioned by the wind blower position, which could cause alterations in the measured emissions of laboratory tests.[16]
To measure emissions during the on-road test, vehicles are equipped with a portable emissions measurement system (PEMS) that monitors pollutants and CO2 values in real time. The PEMS contains complex instrumentation that includes: advanced gas analyzers, exhaust gas flowmeters, an integrated weather station, a Global Positioning System (GPS), as well as a connection to the network. The protocol does not indicate a single PEMS as reference, but indicates the set of parameters that its equipment has to satisfy. The collected data is analyzed to verify that the external conditions under which the measures are taken satisfy the tolerances and guarantee a legal validity.[6]
The limits on the harmful emissions are the same as the WLTP, multiplied by a conformity factor. The conformity factors consider the error of the instrumentation, that can not guarantee the same level of accuracy and repeatability of the laboratory test, as well as the influence of the PEMS itself on the vehicle that is being tested. For example, during the validation of the NOx emissions, a conformity factor of 1.5 (50% over normal tolerance) is used.[17]
WLTP 2nd amendment
In the European Union, the WLTP 2nd amendment is Commission Regulation (EU) 2018/1832 of 5 November 2018.[18]
This regulation is for light-duty vehicles, when heavy-duty vehicles are subject to Regulation (EU) 2019/1242.
Regulation (EU) 2017/1151 sets out the requirements for the device for monitoring the consumption of fuel and/or electric energy. Recorded information includes:
Total fuel consumed (lifetime) (litres);
Total distance travelled (lifetime) (kilometres);
Engine fuel rate (grams/second and litres/hour);
Vehicle fuel rate (grams/second);
Vehicle speed (kilometres/hour).
For hybrid vehicles:
Total fuel consumed in charge depleting operation (lifetime) (litres);
Total fuel consumed in driver-selectable charge increasing operation (lifetime) (litres);
Total distance travelled in charge depleting operation with engine off (lifetime) (kilometres);
Total distance travelled in charge depleting operation with engine running (lifetime) (kilometres);
Total distance travelled in driver-selectable charge increasing operation (lifetime) (kilometres);
Total grid energy into the battery (lifetime) (kWh).[18]
This information is stored by the On-Board Fuel and/or energy Consumption Monitoring device (OBFCM). OBFCM has been mandatory since 2021 on new European cars.[18]
Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is often illustrated as a continuous energy profile. Non-transportation applications, such as industry, benefit from increased fuel efficiency, especially fossil fuel power plants or industries dealing with combustion, such as ammonia production during the Haber process.
The California Air Resources Board is an agency of the government of California that aims to reduce air pollution. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Motor Vehicle Pollution Control Board, CARB is a department within the cabinet-level California Environmental Protection Agency.
Vehicle emissions control is the study of reducing the emissions produced by motor vehicles, especially internal combustion engines.
Emission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over specific timeframes. They are generally designed to achieve air quality standards and to protect human life. Different regions and countries have different standards for vehicle emissions.
A zero-emission vehicle, or ZEV, is a vehicle that does not emit exhaust gas or other pollutants from the onboard source of power. The California definition also adds that this includes under any and all possible operational modes and conditions. This is because under cold-start conditions for example, internal combustion engines tend to produce the maximum amount of pollutants. In a number of countries and states, transport is cited as the main source of greenhouse gases (GHG) and other pollutants. The desire to reduce this is thus politically strong.
A green vehicle, clean vehicle, eco-friendly vehicle or environmentally friendly vehicle is a road motor vehicle that produces less harmful impacts to the environment than comparable conventional internal combustion engine vehicles running on gasoline or diesel, or one that uses certain alternative fuels. Presently, in some countries the term is used for any vehicle complying or surpassing the more stringent European emission standards, or California's zero-emissions vehicle standards, or the low-carbon fuel standards enacted in several countries.
The New European Driving Cycle (NEDC) was a driving cycle, last updated in 1997, designed to assess the emission levels of car engines and fuel economy in passenger cars. It is also referred to as MVEG cycle.
A driving cycle is a series of data points representing the speed of a vehicle versus time.
The European emission standards are vehicle emission standards for pollution from the use of new land surface vehicles sold in the European Union and European Economic Area member states and the United Kingdom, and ships in EU waters. The standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards.
The World Forum for Harmonization of Vehicle Regulations is a working party (WP.29) of the Inland Transport Committee (ITC) of the United Nations Economic Commission for Europe (UNECE). Its responsibility is to manage the multilateral Agreements signed in 1958, 1997 and 1998 concerning the technical prescriptions for the construction, approval of wheeled vehicles as well as their Periodic Technical Inspection and, to operate within the framework of these three Agreements to develop and amend UN Regulations, UN Global Technical Regulations and UN Rules, kind of vehicle regulation.
The fuel economy of an automobile relates to the distance traveled by a vehicle and the amount of fuel consumed. Consumption can be expressed in terms of the volume of fuel to travel a distance, or the distance traveled per unit volume of fuel consumed. Since fuel consumption of vehicles is a significant factor in air pollution, and since the importation of motor fuel can be a large part of a nation's foreign trade, many countries impose requirements for fuel economy. Different methods are used to approximate the actual performance of the vehicle. The energy in fuel is required to overcome various losses encountered while propelling the vehicle, and in providing power to vehicle systems such as ignition or air conditioning. Various strategies can be employed to reduce losses at each of the conversions between the chemical energy in the fuel and the kinetic energy of the vehicle. Driver behavior can affect fuel economy; maneuvers such as sudden acceleration and heavy braking waste energy.
All-electric range (AER) is the maximum driving range of an electric vehicle using only power from its on-board battery pack to traverse a given driving cycle. In the case of a Battery electric vehicle (BEV), it means the maximum range per recharge, typically between 150 and 400 miles. For a plug-in hybrid electric vehicle (PHEV), it means the maximum range in charge-depleting mode, typically between 20 and 40 miles. PHEVs can travel considerably further in charge-sustaining mode which utilizes both fuel combustion and the on-board battery pack like a conventional hybrid electric vehicle (HEV).
A portable emissions measurement system (PEMS) is a vehicle emissions testing device that is small and light enough to be carried inside or moved with a motor vehicle that is being driven during testing, rather than on the stationary rollers of a dynamometer that only simulates real-world driving.
The Not-To-Exceed (NTE) standard promulgated by the United States Environmental Protection Agency (EPA) ensures that heavy-duty truck engine emissions are controlled over the full range of speed and load combinations commonly experienced in use. NTE establishes an area under the torque curve of an engine where emissions must not exceed a specified value for any of the regulated pollutants. The NTE test procedure does not involve a specific driving cycle of any specific length. Rather it involves driving of any type that could occur within the bounds of the NTE control area, including operation under steady-state or transient conditions and under varying ambient conditions. Emissions are averaged over a minimum time of thirty seconds and then compared to the applicable NTE emission limits.
Vehicle regulations are requirements that automobiles must satisfy in order to be approved for sale or use in a particular country or region. They are usually mandated by legislation, and administered by a government body. The regulations concern aspects such as lighting, controls, crashworthiness, environment protection and theft protection, and might include safety belts or automated features.
Government regulation in the automotive industry directly affects the way cars look, how their components are designed, the safety features that are included, and the overall performance of any given vehicle. As a result, these regulations also have a significant effect on the automotive business by generally increasing production costs while also placing limitations on how cars are sold and marketed. Automotive regulations are designed to benefit the consumer and protect the environment, and automakers can face stiff fines and other penalties if they are not followed.
United States vehicle emission standards are set through a combination of legislative mandates enacted by Congress through Clean Air Act (CAA) amendments from 1970 onwards, and executive regulations managed nationally by the Environmental Protection Agency (EPA), and more recently along with the National Highway Traffic Safety Administration (NHTSA). These standard cover common motor vehicle air pollution, including carbon monoxide, nitrogen oxides, and particulate emissions, and newer versions have incorporated fuel economy standards.
Bharat stage emission standards (BSES) are emission standards instituted by the Government of India to regulate the output of air pollutants from compression ignition engines and Spark-ignition engines equipment, including motor vehicles. The standards and the timeline for implementation are set by the Central Pollution Control Board under the Ministry of Environment, Forest and Climate Change.
The EPA Federal Test Procedure, commonly known as FTP-75 for the city driving cycle, are a series of tests defined by the US Environmental Protection Agency (EPA) to measure tailpipe emissions and fuel economy of passenger cars.
The World Motorcycle Test Cycle (WMTC) is a system of driving cycles used to measure fuel consumption and emissions in motorcycles. The methods are stipulated as part of the Global Technical Regulation established under the United Nations’ World Forum for Harmonisation of Vehicle Regulations, also known as WP.29.
Green NCAP is a green vehicle assessment programme hosted and supported by the European New Car Assessment Program in cooperation with European Governments. The Organisation has test laboratories in eight European countries and aims to increase awareness of the environmental impact of the vehicles. The first set of results was released on 28 February 2019.
References
↑ This is the spelling according to the adopted UNECE proposal; variant spellings include "Worldwide Harmonized Light-duty Test Procedures" (according to the UNECE press release).
↑ Agreement concerning the Establishing of Global Technical Regulations for Wheeled Vehicles, Equipment and Parts which can be fitted and/or be used on Wheeled Vehicles Geneva, 25 June 1998
↑ E/ECE/324/Rev.2/Add.100/Rev.3 or E/ECE/TRANS/505/Rev.2/Add.100/Rev.3 (12 April 2013), "Agreement concerning the adoption of uniform technical prescriptions for wheeled vehicles, equipment and parts which can be fitted and/or be used on wheeled vehicles and the conditions for reciprocal recognition of approvals granted on the basis of these prescriptions", Addendum 100: Regulation No. 101, Uniform provisions concerning the approval of passenger cars powered by an internal combustion engine only, or powered by a hybrid electric power train with regard to the measurement of the emission of carbon dioxide and fuel consumption and/or the measurement of electric energy consumption and electric range, and of categories M1 and N1 vehicles powered by an electric power train only with regard to the measurement of electric energy consumption and electric range.
↑ "Insights into WLTP and RDE"(PDF). Volkswagen Group. NOX emissions may equally amount to the NOX value measured on a dynamometer (taking into account a measuring tolerance of 0.5 = maximum amount 1.5)
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