Parents with small children who insist on letting them try to walk up the stairs on the tube/ train/ other busy public areas.
It inevitably creates a tight bottleneck at an area a bottleneck is already going to form. We all have to squeeze into 2/3 of the space while you lead a wobbling toddler up some stairs that are way too advanced for them.
Not only is it horrendously dirty when they sit down on the third step before you heave them back up (always happens) it seems quite dangerous. There is always the chance that someone will accidentally trample them as it’s quite difficult to see in the restricted spaces.
Not least that if I had been able to get up the stairs 15 seconds quicker I would’ve been on my train instead of having to wait for the next one.
AIBU to think that you should carry your child?