This is the dramatic moment a heroic passerby rushed to help a wheelchair user who had crashed on a bridge.

The quick-thinking motorist, wearing a helmet, sprinted towards the elderly man as he struggled on the sloped Mohasawat Bridge in Nonthaburi, Thailand.

Dashcam footage captured by Rattana Janyakorn shows the man approaching the pensioner on March 3.

He first picked up the take-out food that had fallen onto the roadside. When he looked up, he saw the disabled man uncontrollably speeding down the decline, violently bumping against the road barrier.

The rescuer then chased after the hapless wheelchair user and grabbed the handlebars just in time, preventing him from toppling over.

He assisted the man off the bridge and wheeled him to safety on the roadside before returning to his motorcycle, which he had left on the bridge.

Rattana said: 'Heroes don't need to wear a cape to be one, and we are very thankful for the rider who helped. If we can find a place to park, we can go down and help.

'Public roads are for everyone—people walking, riding bicycles, or using wheelchairs. Unfortunately, some don't recognise this. In Thailand, roads often aren't designed for people with disabilities.

'I'm not sure if the elderly man often travels this route. Usually, there are three-wheeled buses here and they can be quite dangerous. I don't know if he has any relatives to help him. I'm very concerned about his safety.'