A pioneer relative of mine is regularly on cart duty.
I've asked her a few times if she has much results but obviously she is quite reticent about being seen to be negative when talking to me. She has admitted that on occasions she has been there for 2 or 3 hours and nobody has taken any literature. Occasionally she'll throw in an vague experience , for example she told me last month about how a former bible study picked up a brochure and is "thinking" about coming back to meetings ( yeah - right. ). Doubtless she'll be spinning this one a bit as a positive experience at the meeting to give the impression that it is better than it really is.
Personally from a marketing point of view I think the trolley concept is probably a good idea , especially in the cities. In fact , when I was an active JW I often wished the Society would have done something like this. The average member of the public will have virtually no contact with JWs but at least if there is a visible presence in tube stations , malls etc then there is some kind of promotional activity , albeit with very limited tangible results.
Lets face it- the results from D-D are very poor anyway. And anyway as we know- the preaching work has never been about results. If it was , JWs would be knocking on doors in the early evening rather than during the day when no-one is at home.