In reply to Jim C:
But that just creates the worst of all possible scenarios for the early mergers, Jim.
If everyone formed two lanes, and there was one 'merge point', in the last 200m before the obstruction, it would be entirely fair- with a 'zipper merge', and no advantage to either lane.
But because people do as you do, and block out the last 200m, to guard against 'queue jumpers', it means that people merge at multiple points over the previous 1+ km. So instead of there being 'one from the slow lane, one from the fast lane, one from the slow lane, one from the fast lane', and so on, it means that there are several people from the 'fast lane' get through for each 'slow lane' early merger- as 'fast lane' users are merging in all the time at various points.
This results in the 'slow lane' queue propagating backwards much faster and being even longer than it would otherwise be; and means the 'early mergers' get hammered with people arriving well after them getting through before them.
If you are worried about 'queue jumpers', exactly the opposite strategy is best- *don't* let anyone in before the last 200m, then let in one person. That way, if everyone in the 'slow lane' did that, a queue would form in the 'fast lane', which would balance out and strip any advantage away from the 'fast lane', and stop queue jumping.
The think is, it needs all your fellow 'early mergers' to take the same approach, but if they did, the whole thing would actually work as it should...