Over the years, we have done on buses and underground trains with our children.
These days, they are older, and perfectly capable of surviving the trip without trouble, but when they were smaller, things were more difficult: with no space for a pushchair, and frequently no space to sit, we had to carry them. This created more problems, because we then had no hands free to strap-hang ourselves.
This is a simple Make that frees up your hands, and gives your children a bit of safe independence.
Step 1: Materials
In the very simplest form, all you need is some cord, but, following extensive market research*, I used about a metre of 10mm "general purpose" rope, and a short piece of 15mm PVC conduit. I also added a slight curve to the conduit by softening it slightly in boiling water.
(*I asked Conker-X)