Traffic Jam Portapotty

I was reading the annos on "Time Well Spent for Traffic Jam Victims" and with all the talk of road cones selling donuts and coffee to people trapped in their cars, I thought of the poor commuter who just has to go.

So these would be about the same idea, quite a bit larger to make room for the facilities, but still small enough to squeeze in between cars. To use it one would just pull their keys out of the ignition, jump out the window, and onto the john's deck. Knowing the DMV, this would probably be a pay toilet.