I usually drive in Eco, I have noticed that in heavy stop n go freeway traffic, I have had several close calls when slowing. It seems to take the car behind me a split second longer to realize I'm slowing which, if they are following aggressively may be a problem. Up until a few weeks ago, my opinion was, hey if they rear end me, that's their fault/problem. That was until I was actually rear ended and after the guy told me he didn't have time to give me his insurance info because his wife was in labor and he fled the scene. I then had have had to suffer through filing a police report, going without a car while it was in the body shop, going without car pool lane access while waiting for DMV to replace the stickers and generally being stressed out over the whole ordeal. My philosophy has undergone a slight adjustment and I now dive in D mode and I am willing to sacrifice a slight decrease in efficiency in exchange for a potential increase in safety.