Barking At People Leaving

Hello. I have somewhat inherited a 9 year old male Pom (not neutered). I've trained (mostly larger lab mixes) dogs in the past, but this little guy is proving difficult.
The most bizarre behavior is that he goes crazy when ever someone leaves the house. He barks, he growls, he jumps against the door in a kinetic fur ball of angst. Normally something like this can be attributed to separation anxiety, but the odd thing is that he does it even with people he doesn't really know. I've done the "get them used to it by going in and out a lot with gradually longer time intervals" method and it hasn't worked. He seems to enjoy going nuts when people walk out the door.
This is proving to be a big problem because it is easy for him to get out the door when someone is leaving. I'm afraid he will bolt down the street (as he has managed to do several times so far) and get hit by a car.
Any suggestions are greatly appreciated.