RIP. Yet another cyclist killed in Southampton, very sad.
On the subject of infrastructure; how much do you think it would cost to put dedicated cycle lanes on Thomas Lewis Way? I think even with a cycle lane, it's such a noisy juggernaut hogging type road that I think cyclists would still avoid it, that said I'd rather have that than a 20mph speed limit along portswood road which imo would be pretty unworkable and unpopular.
The council are already about to spend a few million pounds laying a cycle lane from Southampton Central Station to Swanage, so I'm sure they'd be up for considering proposals to improve cycling infrastructure elsewhere.
I think a cycle lane on TLW would also be a faster way into the town centre, although would need to be properly signposted and accessible.
PS: I also agree with walling off the cycle lane, this would definitely work well on TLW IMHO. You could even have a double lane on the left side of the road, thereby avoiding the right hand turns although not sure how you'd join it and would be stuck on it until you reached St Denys.
Of course, you have to wonder why they built such a big bit of road infrastructure with no consideration whatsoever for cyclists.