In Regulation (EU) No 540/2014 Annex VIII Section IV is stated, that:


Any mechanism to enable the driver to halt the operation of an AVAS (‘pause function’) shall comply with the requirements of paragraph 6.2.6 of UNECE Regulation No 138, Supplement 1 to the original version of the Regulation, 01 series of amendments (OJ L 204, 5.8.2017, p.112)."

The UNECE Regulation No 138 paragraph 6.2.6 -

"Pause function

Any pause function as defined in paragraph 2.7. shall be prohibited"

2.7 says -

"Pause function means a mechanism to enable the driver to halt the operation of an AVAS."

What is purpose then to link to different document, instead of just saying in 540/2014, that Switch for AVAS is prohibited?

The mentioned supplement 1 also says

"Paragraph 6.2.6, amend to read: ‘6.2.6. Pause function Any pause function as defined in paragraph 2.7 shall be prohibited.’"

  • What is an AVAS?
    – ohwilleke
    Jan 26 at 3:07
  • 1
    @ohwilleke "Acoustic Vehicle Alerting System" a system that makes noise in electric vehicles/hybrids to alert pedestrians.
    – user71659
    Jan 26 at 4:13

3 Answers 3


If you say something twice, eventually they’ll be in conflict

Law codes are vast. They deal with many things and sometimes, as here, they deal with the same thing twice. If they duplicated themselves, rather than cross-referencing, every time the law was changed, every single instance would have to be tracked down and changed. Admittedly, that is not as big a problem with digital codes (but still not infallible and definitely time-consuming) but when these would have to be found by hand, it was damn near impossible. Written this way, change it once and it’s changed everywhere.

My first boss taught me that. The fired was engineering rather than law but the principle is the same.

  • 1
    Of course, the problem with this approach is that changes to one law may have unintended and unnoticed consequences for another law that references it. But in this case, the reference is to a specific version of regulation 138 from August 2017. Doesn't that mean that subsequent amendments to regulation 138 will have no effect on 540/2014 unless it too is explicitly amended?
    – phoog
    Jan 26 at 0:04
  • @phoog It does seem like something that will cause a lot of headaches in the future.
    – M. Y. Zuo
    Jan 31 at 19:12

Note the jurisdictions at play.

These are different bodies. The EU regulatory agency is aiming to be conformant with the UN regulatory agency. They are saying "whatever policy the UN comes up with, we're going with that".

This is done because harmonization is good for business. What's bad for business is every State having a different standard that every company in those markets must learn and certify to. If you're trying to sell an EU vehicle in Ukraine or Brazil, and Brazil and Ukraine reference the same UN rules, you're all set.

This allows them to keep up with rapidly evolving technical fields.

It's like a "symlink", or in legal terms it's called Incorporating By Reference. For instance most US states and central American countries have adopted as their electrical code the NFPA's NEC.... rather than write their own from scratch like Canada did. Each State has a tiny list of amendments, but generally products can be built to a national market.

By contrast, the alternative is a "copy-paste" - for instance the nonprofit endowment law UPMIFA was developed by a nonprofit then copied, with occasional modifications, into 49 state laws.

EVs are a rapidly moving field. Technical innovations are flying fast, and responsible central bodies need to make good decisions. Things are ugly if they don't. For instance UL and CSA, who hand in hand write US and Canada rules, decided sufficient safeguards were in place on a special electrician's WiFi login for initial setup of EV wall charge units. Ontario regulators heard "WiFi setup from a phone", panicked, and banned it, making the whole Ontario market more hostile to EVs since most wall units use that feature.

Also, harmonization is good for trade.

When you copy rules, you incur a technical debt where your regulators must constantly check to keep your rules in sync. And this also increases the task load for any company trying to sell into your markets, which deters competition in and out - protects your markets but cages your manufacturers.

Such protectionism tends to be discussed harshly at trade conferences such as G20 or GATT. "We literally incorporate UN rules" (why don't you) is an excellent rebuke.


Just complementing DaleM's answer, the principle is called DRY (Don't Repeat Yourself). Although this formulation primarily belongs to the domain of software engineering, it perfectly fits law as well.

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