YOUNG men who speed do so because they have a small penis - or so the new RTA road safety campaign implies.

Ads from the $1.9 million campaign - which targets speeding among 17- to 25-year-olds - aired for the first time on TV last night. They show onlookers who see speeding male drivers wiggling their pinkie fingers.

The gesture represents a small penis in youth culture, but even an elderly woman employs it.