One goal of the connected vehicle program is to raise the situation awareness of drivers to unseen events in the driving environment. Warnings of unseen threats may prompt a directed visual search for that threat at the expense of overlooking other intervening threats along the way. This study assessed the distraction potential of alerts to unseen threats. Twenty-two participants drove an instrumented vehicle on a closed course and encountered threat situations, such as a car entering the road from a side road obstructed from the driver's view. On each pass, there were two sandbags that served as secondary threats, and the driver was instructed to press a response button whenever one was detected. The control condition bags were placed at locations on the course where the driver was undistracted and encountered no primary threats. The threat bags were positioned so that they became visible shortly after the warning of a primary threat appeared on an in-vehicle display but before the primary threat became visible. The results showed that advance warnings improved primary threat detection time. That is, when drivers were given advance warning of the presence of an upcoming threat, the drivers identified the presence of the threat sooner than when no warning was given. Unfortunately, this facilitation came at a cost of reduced detection distance and reaction time to the secondary threats that were present in the roadway. Future research should investigate whether this effect persists for more critical secondary threats.