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Drivers often floor it at the lights, a large number switch off their start/stop systems, they might idle for an hour to listen to the radio, exceed the speed limit and exhibit other inefficient driving behaviour.

Do the European Union's RDE tests factor in real world driver behaviour or do they only demonstrate the emissions of real world best practice driving?

  • Can you add more information about which region you are referring to, the EU standards are quite different to US standards, and the testing regimes are different accordingly. In the EU tests for NOX emissions there are ‘not to exceed limit’ tests, so it doesn't matter how inefficient the driving is, if the emissions exceed the limit then the vehicle fails. It should be possible for the vehicle (as designed) to exceed the limit. – Christopher Gilmour Oct 31 at 16:05
  • Thanks for your input, I just updated it. Did you mean to say that it should NOT be possible for the vehicle to exceed the limit? – atreeon Oct 31 at 17:03
  • I think it does make sense to measure the fuel consumption for best practice driving as bad practice can be arbitrarily bad (idling). As a rule of thumb, I've heard that good vs. bad fuel efficiency driving habits result in a factor 2 (!) in fuel consumption. That's like VW Fox vs. Amarok real life average diesel consumption reported on Spritmonitor (which is still probably confounded by fuel-saving drivers probably being more likely to drive a Fox than an Amarok). – cbeleites supports Monica Nov 3 at 20:32
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    Wrt. emissions: I think we can (could) know this more easily from macro-economic statistics. Factor 2: sorry, no hard reference. It is a rule of thumb I learned in driving school (fuel economy is mandatory topic here since > 20 years). But it is also not unplausible compared to the range seen on spritmonitor (which also includes variation due to other factors such as hilly vs. flat landscape, rural vs. town etc. but as I said is probably biased towards fuel saving people, so also biased towards showing too low variation in fuel consumption due to driver style). I found some newspaper artole... – cbeleites supports Monica Nov 5 at 19:35
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    ...(zeit.de/mobilitaet/2017-11/spritverbrauch-auto-fahrer-fahrweise, in German) that says "prudent driving behavior" saves 30 % [compared to normal/standard/usual driving behavior] and go on discussing a number of choices in detail (e.g. saying economic choice of gear saves 10 - 20 %, etc.). It is not clear, though, which factors they include in "driving behaviour" (I'd say tire pressure and AC/heating are important important for fuel economy, but I would not call them driving behavior). Normal driving ±30% for behavior would again mean imprudent : prudent fuel consumption ≈2, btw. – cbeleites supports Monica Nov 5 at 19:48
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Under RDE [Real Driving Emissions test], a car is driven on public roads and over a wide range of different conditions..... Conditions include:

  • Low and high altitudes
  • Year-round temperatures
  • Additional vehicle payload
  • Up- and down-hill driving
  • Urban roads (low speed)
  • Rural roads (medium speed)
  • Motorways (high speed)

Source: https://caremissionstestingfacts.eu/rde-real-driving-emissions-test/

More details are mentioned in this article:

The 1.5- to two-hour test (over around 50 miles) has an equal split of urban, rural and motorway routes, takes into account stops/starts in towns and must exceed 56mph on appropriate roads. ... The goalposts for RDE will keep moving, too. For example, at the moment, manufacturers must sign a legal document stating that the RDE results can be achieved in certain conditions, such as an altitude of up to 700 metres. From 2021, that will extend to 1300m.

So the answer to your question is: tests include real driver behavior, but not any of the inefficient habits you mentioned. Since manufacturers have to perform the test themselves they won't do anything (outside of the test requirements) that will have a negative effect on the outcome of the test.

  • thank you for such a great reply. Yup, I thought that might have been the case. With that information I would think that driver education, enforcement and ethics while driving is just as important as having a car capable of driving at low emissions. – atreeon Nov 1 at 15:14

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