Avoiding eye contact is an unwritten rule on the Tube, but is seems in San Francisco, where this heartwarming photo was taken, commuters are a little more friendly.

A touching photo of a woman helping a young boy tie his tie while travelling in the California city has been widely shared online.

Reddit user Loozar, who captured the moment on camera, explained the woman noticed the boy was struggling and offered to help.

“Kid was desperately trying and failing to do it himself and a fellow passenger asked if he needed help,” they posted.