i can see though that winter tyre users could be more likely to crash than people who don't. I won't be fitting winter tyres, as I live on the south coast, and for the 3 days a year it's snowey, I just won't drive. Someone might live next door to me but be yomping up and down the country, and gets the tyres because when its snowing, he needs to get to work over the downs.
He's doing the safe thing by fitting the tyres, but he could be more at risk by doing so. Its the same as fitting better brakes to a car, or improving the handling. In itself, it makes the car safer, but in doing it, you're now in a catagory of drivers more likely to crash