Captains could do it off their own bat I guess, agree to face the same number of overs (98 x 3 = 294 overs for match, making for 147 overs in total over their 2 innings). Then at the end, either the 4th innings team gets the total, or they declare their innings closed in the last over and admit defeat so that the game gets a winner.
It's a broader idea that has been floated before, having a limit on the number of overs in an innings to get batsmen playing more shots especially at the end. I heard one idea for 100 overs limit, I guess 120 would be more realistic for a Test match.
Problem is I can't see both sides using 147 overs so there'd be reluctance. Whether they can simply agree "off their own bat" I doubt or they might just decide to do it so they get their match fee and time off with no consideration for the organisers/crowd.
If England had held their catches, or dropped/rested Bell which I'd been advocating for a while now, then this match could be well into the England innings already.
You'd have to look in the rules to see whether there are any about agreeing to waive innings in internationals, domestic cricket no doubt, but there's no spectators or much money in the average county championship match. Also there may be considerations like how England in this instance could get a win that playing a full match they wouldn't, windies for starters might not want to lose and for seconds other teams wouldn't like the chances of one or t'other getting a result they themselves might not be able to agree with more stubborn sides.
The series situation makes it look like a good opportunity to play one innings aside, but if it were a series decider would it seem such, and should it be allowed? If one side were 1-0 up they wouldn't agree to it, so in my books if it isn't going to be agreed in all circumstances it shouldn't be agreed in any circumstances. If they called it a draw and played two one-dayers then fair enough.
Oh and FWIW I don't agree with contrived results in championship matches
It's a broader idea that has been floated before, having a limit on the number of overs in an innings to get batsmen playing more shots especially at the end. I heard one idea for 100 overs limit, I guess 120 would be more realistic for a Test match.
I've been an advocate of trialling/playing a one innings limited overs match of say 100 overs a side for a long time, getting on must be 20 years I reckon. Have the tactical nuances of having bowling allocations of 20 overs maximum so you have to decide on five bowlers or say play four and gamble that the fifth bowler allocation isn't needed (if you bowl the opposition out inside say 60-70 overs), or you get away with a part-timer, and the balance of batting. The tactics in-game would be fascinating, not knowing if you will get to the full 100 overs so it would be a question of pacing it right with the aim early on to survive and then looking how much you can accelerate without the last 10 overs being close like they are in limited overs.
And even if you got bowled out for say 200-250 you'd still be in with a shout, you can use your best 2-3 bowlers early and say 40-50 of their overs first. I think it would be even more tactically fascinating in the subcontinent, or damper conditions in England. With pitches only needing to last 2-3 days you could get much better matches, even pitches taking spin on the first day. It'll be a sad day if muppets who would do away with longer versions of the game ever got their way, there's tactics in 50 over games but it's too short, there's little scope for tactics in bash bash bash 20 overs games, no time to rebuild and it favours certain types of bowlers too much. IPL is too repetitive for words, even 50 overs can be too much bash bash.
The advantage to 100 overs is sides could see a decent batting surface and push on early yet have to dig in to bat out their overs later on if they went from say 50/1 off 15 overs to 230/4 off 45 overs, to 260/7 off 55 overs.
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To get a result from here will be very difficult, England or more precisely Bell have dropped too many chances to get into the windies early and I doubt the windies can knock over England quickly twice.
Best hope England have is that they get two full days cricket, finish windies off quickly and get maybe 150-200 in front by lunch tomorrow and hope for the best.
For windies I'd say they need to get at England early this morning, even consider declaring overnight, and hope to knock them over for 150-200. They have the harder task batting first as they have to set targets, that is without any realistic hope of enforcing the follow on so to win they'll likely have to bat twice. England could bat once and a bit, depends how it goes with the respective bowlers and batsmen.