I don't want to sound like I'm beating a dead horse, just wants to share some information on the Smart car and rear facing seats. I'm assuming the model that your child is riding in is the ForTwo and if that is the case a rear facing child seat can NEVER, EVER, be installed there. Despite having sensors and it looking like the airbag is initially shut off, there is a high likely hood that the dynamics of a crash could (and would) trigger the airbag anyway. That would be absolutely devastating to any child in the rear facing seat. It isn't even just a risk of serious injury, she would have no chance :-(
The only time a rear facing seat can be used in the ForTwo model is if you are using the car safety seat that was designed by Mercedes (the parent company) for that car. They built into the car safety seat a chip that will completely deactivate the airbags on the passenger side when that car safety seat is installed. Unfortunately, that product is not available here in N. America.
I'm really not trying to use scare tactics and sensationalism to get my point across. I'm sure you are just trying to figure out the best in a less than ideal situation. But, not only is it extremely dangerous to install a rear facing seat in front of an airbag, it is likely illegal as well. There have been cases of parents being criminally charged and prosecuted when they put their rear facing child in front of an airbag, it deployed, and the child died. It's just not worth the risk. The consequences are too catastrophic.
I do completely understand the headache of working out the logistics of needing your kid to be in several different cars. Between my work schedule and hubby's work schedule, my kids are in 5 different cars in any given week. It's super annoying. And stressful. But there we simply some situations that absolutely cannot happen (rear facing seat in front of an airbag) no matter the circumstance.
Child Passenger Safety - Instructor
DS1 - 8 DS2 - 7 DS3 - 3
Expecting a SurroBaby 12/12/13