Overview
Starting in 2017, the Real-Driving Emissions (RDE) test became part of the type-approval procedure for all new passenger cars and vans. The RDE test is an on-road emissions test meant to complement laboratory tests to ensure vehicle emissions are similar during normal, real-world operating conditions as they are during laboratory testing. The RDE regulation was adopted in four packages between 2015 and 2018.
Background
The RDE test uses portable emissions measurement systems (PEMS) to collect data throughout a test trip. A valid trip must contain all required components of a valid trip and satisfy all boundary conditions.
| Total trip duration | Between 90 and 120 min | |
| Distance | Urban | >16 km |
| Rural | >16 km | |
| Motorway | >16 km | |
| Trip composition | Urban | 29% to 44% of distance |
| Rural | 23% to 43% of distance | |
| Motorway | 23% to 43% of distance | |
| Average speeds | Urban | 15 to 40 km/h |
| Rural | Between 60 km/h and 90 km/h | |
| Motorway | >90 km/h (>100 km/h for at least 5 min) |
| Payload | ≤90% of maximum vehicle weight | |
| Altitude | Moderatea | 0 to 700 m |
| Extendedb | Between 700 and 1300 m | |
| Altitude difference | No more than a 100-m-altitude difference between start and finish | |
| Cumulative altitude gain | 1200 m per 100 km | |
| Ambient temperature | Moderatea | 0°C to 30°C |
| Extendedb | From –7°C to 0°C and 30°C to 35°C | |
| Stop percentage | Between 6% and 30% of urban time | |
| Maximum speed15 | 145 km/h (160 km/h for a maximum of 3% of motorway driving time) | |
| Dynamic boundary conditionsc | Maximum metric | 95th percentile of v*a (speed * positive acceleration) |
| Minimum metric | RPA (relative positive acceleration) | |
| Use of auxiliary systems | Free to use as in real life (operation not recorded) | |
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aModerate driving conditions are subject to the normal RDE test emissions limits bExtended driving conditions are still allowed to count towards a valid trip, but the pollutant emissions (excluding CO2) measured must be divided by 1.6 before evaluating compliance with emissions limits cDynamic boundary conditions are used to measure if a trip is driven too aggressively or too smoothly at any point. A vehicle exceeding the maximum metric is driven too aggressively while a vehicle below the minimum metric is driven too smoothly. The figure below shows how compliance is determined for dynamic boundary conditions. |
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The following figure from the ICCT graphically shows how dynamic boundary conditions determine if a trip is driven too aggressively or too smoothly.
To evaluate the test validity, a method calculates CO2-mass-based Moving Average Window (MAW) of the trip. The CO2 emissions from the WLTP test is used to create a characteristic curve. The RDE trip is considered valid if at least 50% of the urban, rural, and motorway windows are within the allowed tolerances of the curve.
To report trip emissions, the ratio of CO2 emissions from the RDE test to CO2 emissions from the WLTP test is calculated to evaluate emissions. If this ratio (rk) is ≤ 1.3, the raw emissions from the trip are reported and evaluated. If rk > 1.3, the raw emissions are downscaled as a function of rk before being reported.
The not-to-exceed (NTE) limits for regulated pollutants for RDE tests is defined by the formula below:
NTEpollutant= CFpollutant * EURO-6
Where CF is a conformity factor and EURO-6 is the Euro 6 emission limit in mg/km. The conformity factor allows for vehicles to emit by a certain factor above the Euro 6 emission limit when driving on the road. Conformity factors are shown in the table below:
| NOx | Particle number (PN) | COa | |
| Euro 6d-Tempb | 2.1 | 1.5 | – |
| Euro 6d | 1.5 | 1.5 | – |
| aCO emissions are measured as part of RDE tests but are not subject to any NTE limitbEuro 6d-Temp refers to the temporary CF for NOX emissions | |||
Since 2018, a new Global Technical Regulation (GTR) and UNECE Regulation on RDE have been under development to harmonize the application of the method beyond Europe.
