Ha!  No.  None of the boats has "not reached the zone."
Perhaps TTR 18.2(a)2 should refer to "the boat that has not reached the zone or is clear astern at that
moment"

It would seem that TR 18.2(a) does not apply and TR18.2(e) would apply ... when they do become overlapped at some later point in time.

If all boats actually reach the zone simultaneously without any overlap then at the instant they all enter there is no "boat that has not reached the zone" so I think no boat owes mark-room under TR 18.2(a)(2). So I'd say the situation rolls to TR 18.2(e). Yellow and Blue owe mark-room to Green and Blue owes mark-room to Yellow

That said, all boats reaching the zone simultaneously without an overlap seems unlikely to occur and impossible to prove. Each boat will claim that they were first to the zone Yellow and Blue will claim no overlap. Blue and Yellow will presumably soon be turning toward the mark creating an overlap between themselves and with Green. How do they prove that they reached the zone before creating the overlaps? Becomes even more difficult in a mixed fleet where boats are of different lengths. So PC would probably want to try to find facts as to what order the boats reached the zone and then apply 18.2(a)

Yes.
Wouldn't 18.2(b) Apply?   If a boat is clear ahead when she reaches the zone, the boat clear astern at that moment shall thereafter give her mark-room.    So Blue is entitled to head up sail to the mark after entering the zone and Green and Yellow are not entitled to room.

Everyone .. please use "TR" and "RRS" prefixes on your rule references so we know that everyone is talking about the same thing.  Thanks! - Ang

18.2.a says: When boats are overlapped the outside boat shall give the inside boat mark-room,..... None of the boats are overlapped. 
For RRS 18 to apply, this condition has to exist: ......and at least one of them is in the zone.   None on these boats is 'in the Zone' (yet). No RRS 18 here, only RRS 12.
Now, like Tim says, add water to it and get ready to listen to stories.

I think it is convention that with such a diagram, the following are equivalent:

I think it was intended with this diagram that all 3 boats are a) "in the zone" and b) entered the zone at the same time so that we could excercise the applicability of TR 18.2(a)

Chris

Or "exorcise."

Club racer, no expert here……The RR18.2(b) refers to CLEAR AHEAD & CLEAR ASTERN.  THE TR18.2(a) does not.   So the question is does TR18.2(a) apply?   I’m thinking no, then Rule 12 in effect.   If boats have touched the edge of this pictorial zone, then TR18.2(a) (2) applies, Blue has Mark Room as not overlapped with Yellow & Green.  

This is clearly a hole in the new rule.  I think the solution would be to replace the words 'that has not reached the zone' with 'is clear astern' in Test Rule (TR) 18.2(a)(2).  It also makes the argument about who reached the zone first moot.  That isn't important in match racing with umpires to make that call, but it is in fleet racing.  I think this is something that the sailors will easily be able to apply at a mark.  If you are approaching the zone or you think you are at the zone, you can look around and, barring the creation of overlaps with another boat already in the zone, if you are overlapped and inside or clear ahead you get room from that boat.  If you are overlapped outside or clear astern you give room to that boat.  The goal of the rule changes is to have something this simple to apply on the water at a time of great stress.

If we make this change then this situation resolves itself very easily.

I think the other situation that this change would bring up is this one:

If we change the wording as I suggest then Blue would be entitled to mark room from Yellow.  The further you move Blue to the left the less Yellow will have to do to give room.  The closer Blue is to the zone the more Yellow would have to do.  But Yellow and Blue don't have to worry about figuring out who entered the zone first.  This would be a change in who gets room under the new rule.  But interestingly enough, this scenario is *not* handled by the current rule as the current rule only tells you about a boat that is clear ahead when she reaches the zone.

I think the diagram intends to convey that some part of each boat's hull is in the zone when this snapshot is taken, and that they all entered the zone simultaneously.

One thing that puzzles me: With RRS 18.2e we have last point of certainty which makes it fairly clear to decide which boat has mark room, even if its hard to judge the zone. With TR 18.2a.2 It seems to me that which boat has mark room depends entirely on a judgement call by both crews on which boat reached the zone first, and there is no last point of certainty possible. Am I correct? If so then its possible to imagine a situation where clear ahead is well wide of the mark, making a wide out close in rounding, and clear astern gains mark room without being overlapped. This seems such an obvious point I can't believe the working party hasn't considered it, so it would be interesting to know what the thinking is. Or have I completely misinterpreted the test rule?

I sail very fast small boats, and at the moment RRS 18.2e means that at 5 or 6 boat lengths out from the mark one may confidently predict who will have mark room and who will not. If I understand the TR correctly then that confidence evaporates, and one is left with crews possibly disagreeing on a judgement call in a matter of fractions of a second in (given a downwind mark scenario as sketched) what is already a tricky boat handling manouver.

John C .. Have you done the TR "Test Quiz" yet?

Everyone should go through all the materials ... the Test Quiz, the known "Game Changers", etc. 

Question 5 of the Test Quiz addresses this issue.

Test Quiz here: https://www.surveymonkey.com/r/22G2XN3

I'm not sure Question 5 completely addresses the issue at hand, and I'm not sure that its completely accurate to say there is no game change.  In Q5 SA gybes before reaching the zone, and is therefore overlapped when she reaches the zone, hence in current RRS she is not entitled to mark room, and there is no game change. However if you take Boris/Angelo's sketch above, leave out Yellow and have Green reach the zone before Blue, then I believe that Blue is clear ahead when *she* reaches the zone, and is entitled to mark room under RRS18, but because Green reaches the zone first Green is entitled to mark room under TR18, and there is a game change. That isn't itself a problem, but my major concern is that, if I understand this correctly, there is no last point of certainty for who is entitled to mark room, so the PC is stuck with having to decide whether blue or green touched the zone first, and I cannot see that there will be any reliable evidence for them to make that determination with.

Ang - I did the test quiz during Dave's talk last week.  I cannot claim to have done a deep dive on the new rule yet, creating my own scenarios, etc. but I have read through the documents.

For the scenario I diagramed, my point was that with the new rule as proposed, Yellow gets mark room as the first boat to the zone.  If the wording change that I proposed were to be adopted, this would change to Blue getting mark room.  I also note that the current rule doesn't explicitly cover this situation in 18.2(b).  It covers the case where the first boat to the zone is clear ahead, but not the case where the first boat is clear astern.  You would have to revert to 18.2(a) for that in which case Yellow would get room once Blue gybes.

John re: "the new rule as proposed, Yellow gets mark room as the first boat to the zone.  [...]  I also note that the current rule doesn't explicitly cover this situation in 18.2(b).  [..]  You would have to revert to 18.2(a) for that in which case Yellow would get room once Blue gybes.

Roger that.. so the new TR and the current RRS both give Yellow MR .. so no game change here.   I think the authors would argue that the game is the same in this instance, but the clarity of who gets MR improved.  Yellow is first to the zone, no overlap, Yellow gets MR directly from TR 18.2(a)(2) without having to "revert" to RRS 18.2(a) after exhausting all other options.

Maybe this makes my problem clearer. 
In the L/H pic Blue has reached the zone before Green, in the R/H pic Green has reached the zone before Blue.
If I understand things correctly then:
Under RRS 18.2b Green is entitled to mark room in both situations (provided she is still clear ahead when she reaches the zone in the L sketch).
Under TR 18.2.a.2 Blue has mark room in the left sketch, and Green mark room in the right sketch, and there is no last point of certainty to assist competitors or PC with establishing which applies. 

John and Jim .. the light-bulb just turned on over my head .. thanks for your patience. - Ang

I think Jim's diagrams are a great illustration of a problem of the new rule and the kind of thing we want to avoid.  I am not too concerned about changing the game in some cases, especially when it makes it simpler overall to figure out who gets room and who doesn't.  I think the determination of who reached the zone first is going to be a very hard thing to do on the water.

What about a variation on RRS 18.2(e)?

"If boats are not overlapped and there is reasonable doubt as to which boat reached the zone first, it shall be presumed that the inside boat is entitled to mark-room" (probably simpler for competitors to understand and safer, seems closer to the intent of the TR)

or

"If boats are not overlapped and there is reasonable doubt as to which boat reached the zone first, it shall be presumed that the boat clear ahead is entitled to mark-room" (would preserve the current game)

Tim - while I understand what you are trying to say, to me this adds one doubt on top of another.  We already have one rule dealing with doubt over whether an overlap exists and now we are adding one about reaching the zone first which is dependent on something else with doubt.  I think we need to remove the question about who reached the zone first from the new rule.  After all, our goal is to simplify things.

Yeah, John, I see what you're saying as well. But it seems like that pretty much leaves us with the status quo, and still the controversy about whether an overlap did or did not exist when the first boat enters the zone (which 18.2(e) tries to give the PC a tool to resolve).

Trouble is unless you have been party to all the discussion its hard to know what other nasty gotchas the writers avoided that we don't know about. I like the game in the current rule that if you are clear behind at the zone you don't get water, and I like that there's a clear last point of certainty. On the other hand I really like the simplicity of the test rule, but I'm not sure its practical. Still, that's at least partially the reason why test rules are issued. I've tried a few options in my head, but they've mostly turned out to be barger's charters. 

I agree that in the situations diagrammed, the TR will be almost un-umpirable, let alone all but impossible for competitros to assess.

The discussion seems to have overlooked Case 2 which matches John C's first diagram.  B is required to give Y mark-room whether under RRS or TR.  Obviously the TR drafters didn't want to change that.

John C's proposal to reintroduce Clear Astern would change Case 2.

I think that Tim is on the right track with an additional presumption in TR 18.2(c).

While I agree that my suggested changes would change case 2, is that a bad thing?  If we are going to simplify the rule we have to accept that some changes will happen.  From a practical point of view, the farther Blue is from the mark the less Yellow will have to do to give Blue room, i.e. Yellow will be able to sail around the mark ahead of Blue in 'room freely given'.  The closer Blue is to the mark the more Yellow will have to do to give Blue room.  The point is that the rule becomes simpler to apply.  If I am on Yellow when I hit the zone, if a boat is clear ahead or overlapped inside of me, they get room.  If a boat is overlapped outside or clear astern, they have to give me room.  That is the kind of simplicity that we are looking for.  I can easily accept that small change in the game if I don't have to worry about who got to the zone first.

I agree that changing the game in a minor way in fringe conditions shouldn't be regarded as an issue, but I suggest that your drawing/case 2 situation, taken to extremes, can bring about a situation where a boat that, although nominally clear ahead when the other boat reached the zone, is outside and behind a boat that was always nearer the mark when they actually reach the mark. I submit that is a situation just as undesirable as the difficulty in establishing which boat reached the zone first. In a race with boats that sail hot angles downwind I suggest that this will be a reasonably common scenario. See this sketch for instance.

So I think it right that, as in RRS, a boat that is overlapped on the outside when *she* reaches the zone should not be entitled to mark room. I just wish I could think of an elegant wording to suggest.  I tentatively suggest something that works like this, but I think its too clumsily worded.
(a)
(1) When the first of two boats reaches the zone, and the boats are overlapped the outside boat at that moment shall give the inside boat mark-room.
(2) When the second of two boats reaches the zone, and the boats are overlapped the outside boat at that moment shall give the inside boat mark-room.
(3) When the second of two boats reaches the zone and the boats are not overlapped the boat clear behind at that moment shall give the boat clear ahead mark-room unless (1) applies.
I have an uneasy feeling there's a scenario I have missed in that.

To me, we would just be adding more complication onto the new rule with all the conditions we are adding to cover cases.

I think our goal is that 1) when the first of two boats reaches the zone that the room issue is a) very easy to determine and b) set for the rest of the rounding, and 2) if it is hard to tell who reached the zone first, it shouldn't matter, the room issue needs to be resolved in the same way.  If we don't accomplish that we haven't improved things.  Small changes to the game are a small price for simplicity.

If the boats in your diagram are going approximately the same speed Blue will be around the mark a couple of boats lengths ahead of Green and Green will have plenty of mark room.  The faster Green is relative to Blue the closer we get to your situation where Green is going about 2x as fast as Blue.  As the boat closer to the mark, in distance but not time, when Blue enters the zone, she knows who she has to give room to (Green in this case) and can plan accordingly.  That is the real key, Blue and Green can plan their roundings relative to one another.  But if Blue knows she has to give room to Green, why would she put herself in this position?  Also, if Green is that much faster then she wants to avoid being trapped behind Blue like this.  If I were Green, knowing that I was entitled to mark room, I would probably go outside Blue and be annoyed but would just get on with my race.  Blue will be in my wake quickly enough.

If the TR 18 prompts so many exceptional cases, then it is not a good rule.
Might there be simpler wording for the existing RRS 18? 
Mark room without ROW is not so bad... It just requires discipline.