Originally Posted by CAP493
Whilst this is indeed the requirement set out in MATS Part 1 (and derived from ICAO Annex 11) it's nowadays a highly dubious procedure. Expecting the flight crew of a high-performance glass-cockpit aircraft operating in complex terminal airspace, often adhering to onerous noise abatement requirements, to adopt a 'see-and-be-seen' technique against VFR traffic is frankly, a nonesense.
In another place the difference between the UK and US rules and airspace structures was summarised as ' The US believes see and avoid works, the UK doesn't believe it works'.
Where I grew up and learned to fly (KHPN), handles 180k movements a year (6.5 x Solents I think) in a class D zone, about the size and shape of a MATZ, and without the ability to refuse a zone transit (i.e. operated to ICAO spec). These movements are a wide mix of traffic, but with a lot of commercial and heavy biz jet traffic.
This philosophy difference appears to drive part of the relatively higher cost/movement of ATC in the UK vs. US and the very binary airspace structure (highly controlled or 'not' controlled)