Tactile alerts have the benefit here because you don't use your sense of touch while you're driving, even though (skin) is the biggest sensory organ.

Touch is completely unused at the moment,

We think that touch is so completely unused at the moment. We need something else other than sound and I think touch is the really exciting thing to work on,

It makes sense though,

I have this weird allergy where metal can't touch my skin.

This research represents a whole new way of thinking about the design of warning signals for car drivers,