Possible use of nvidia-docker: As container or as container-runtime installed on host

Dear Developers,

if you can help me I would be glad.
I want to benchmark a HPC-system with MLPerf for masterthesis. On this HPC-system I’m not a SuperUser (and there isn’t a fakeroot option) and docker is not available. I have to use singularity containers. I know how to use docker-container with singularity.
What I saw on launch training README.md
the benchmark can be started with nvidia-docker.

The question is: Docker-runtime must be installed on host system. Is it the same for nvidia-docker, or is it possible to use nvidia-docker out of a container (e.g. like NGC) ?