My Twizy was bought partly to cover the school run-a 4 mile round trip down muddy rural lanes which are narrow and lethally slippery. We take a 4 year old to school and a 2 year old to nursery the opposite direction on town roads. We use a Graco Junior Maxi seat and the Twizy’s rear belt.
We almost bought a Winther Kangaroo or Bakfiets Cargo and the Twizy is a much better solution, see:
My view is that it is certainly not a safe as a car, and the following should be considered:
1/ crush injuries from a rear impact, but the frame is stronger than some may think and the Twizy is light enough to be “bounced” rather than taking 100% of the impact
Also bear in mind that many children travel in the rearmost seats in Zafiras etc, inches away from the rear window…
2/ facial injuries for the rear passenger hitting the hard back of the front seat in a frontal impact-there should be a soft covering on the rear seat back
3/ very little side impact protection at bumper level
4/ the open sides leave you vulnerable to flying debris if an accident happens near to you
However, the Twizy is light, narrow and manoueverable and there is little weight/momentum to absorb in an impact-and it is safer down our narrow lane than walking, bike, scooter, motorbike etc. Importantly, as it is so usefully narrow, I can pass other vehicles in the narrow lane without them having to stop-unlike in a car, where I have had various close shaves from other people going too fast and not being able to stop.
As such and at the low speeds and conditions that my children are carried, I feel it is acceptable.