:roll: Would be helpful if you would indicate your geographical location... the "Signature" facility in PriusOnline is a super place to provide that information in each of your posts. I would also suggest providing the pertinent info on your Prius... yr model, package, etc.
Do you mean the amber signal that looks like an asterisk (snowflake) on a departing highway? If so, that indicates that the outside temperature is 34º F or less... a notice that ice could make the highway slick. Your location would help indicate whether you live in an area where that temperature is likely.