Car seats - if one child is in the front seat, which car seat is best?

[mrsrdowneyjr]

I will shortly have a 4 year old, a 2 year old and a newborn, all in age-appropriate car seats. Whilst they can all be squeezed in the back of my car, if I have to put one in the front seat, which one would be safest? I know it is best to have all in the back, but sometimes this just may not be practical. Any advice appreciated.

I take it you've disabled the airbag (if you have one)?
My gut instinct is to put the newborn in the front as the rear facing seat is the safest of the three, esp if the 4yo is in an adult belt not a harness.