Four cycle commuters from the Alzheimer's Research Trust in Cambridge this week started an experiment into the possible road safety benefits of wearing the colour purple. Or to be more precise purple Alzheimer Research Trust (ART) t-shirts. The experiment came about when Andrew Scheuber, who works for the trust, noticed that motorists seemed to give him more room when he was wearing his ART t-shirt on his commute to and from work. He mentioned this to a colleague who said that her husband had said the same thing, in fact says Andrew: “He went further, because he'd noticed that our white t-shirts didn't produce the same effect: it only seemed to happen when he wore the purple one.” While Andrew is happy to acknowledge that experiment is partly a way of raising the trust's profile he is quick to point out that this does seem to be a genuine phenomenon. The Alzheimers Research Trust encourages employees to cycle to work because a healthy lifestyle can help reduce the risk of developing Alzheimers, so anything that might boost safety is worth pursuing. So what will the ART commuters be doing to test their theory about the colour purple? “Four of us are going to ride in to work on our normal commutes for the next two weeks, two will wear the purple t-shirts on week one while the others will wear the trust's white t-shirts, then the following week they will switch around and see if we notice any differences in driver behaviour from one week to the next,” explains Andrew. For what it's worth our pet theory is that purple is an unusual colour to see on the roads, where many cyclists and workmen wear high viz yellow, that it registers more profoundly in a driver's brain and he or she moves out accordingly. There has been some talk that high viz signage and clothing is now so common that for many road users it has just become an accepted part of the roadscape so while they might see it, they don't notice it as much. Mind you, purple is not likely to work so well in the dark. That's what we think, have you got any theories on this one? Andrew will report back on how the experiment goes in a couple of weeks.