I drive in London regularly and I'm always thankful for the cyclists who wear hi viz. I'm much more likely to notice a bright yellow/Scotchlite clad cyclist ahead on my left hand side than one who isn't. Lights help, but hi viz makes a big difference.
Bless. I'm so touched by the attitudes of drivers who 'notice' things like me. It seems like an implicit admission that a driver isn't actually actively looking for cyclists but is bimbling along concentrating, if it can be called that, on the important stuff, like HGV's, who else in the jam has a better car, the legs on the pedestrian passer by, or the driver's mobile phone call, etc.. But I'm sure that is not what you meant.
~Turing to your main point. The little available research suggests otherwise. Some even suggests that in the dark black+reflectives on moving parts of body/bike is more effective. Some even suggests that in certain light conditions low sun, wet road, hi-viz is part of the problem.
Either way, if they ain't looking they ain't goinna see you, no matter what, and if they are looking you don't need hi-viz. Seeing someone a mile off in their flourescent outfit is no guarantee you'll remember them once they are within your effective stopping distance or give them 3ft as you pass them. ime anyway.
