The mystery of why malfunctioning traffic signals have been causing chaos for motorists in Greater Manchester for some weeks has finally been revealed – and it turns out slugs are to blame.

Despite being fixed or replaced, the lights at the Robin Hood crossroads in Stretford, Trafford, have repeatedly failed, with three dangerous incidents reported in the space of a year, says the BBC.

Engineers were initially baffled, but Transport for Greater Manchester has now found the issues were caused by slugs “entering the signal controller, causing short circuits.”

“This was the first time the highways team had ever experienced this,” said Councillor Steve Adshead.

It is thought the slugs were crawling inside the traffic lights for warmth, before being killed by the electrical systems which power the lights.

“For them to go several times less than a couple of years old seemed very odd,” Adshead added. We had a couple of residents raise it with us saying ‘why do these lights keep going?’

“I had to push Transport for Greater Manchester on it quite a bit.”

Despite initially being unable to pinpoint a cause and more than a year after Adshead raised the alarm, TfGM eventually got back in touch with an explanation.

In a letter, they said: “With the exception of one outage caused by a road traffic collision, the faults shared the same underlying cause. Slugs had entered the signal controller and caused short circuits.

“Remedial works were undertaken in July 2026 to address this issue. Since these works were completed, there have been no further signal outages at this location.”

(Picture: Gina Sanders)