When the electrons cross the junction, they drop from the higher energy level to the lower one, and the energy each electron loses when it drops takes the form of light to a large extent.
Local campaigners, cyclists and bloggers have highlighted the safety issues of the junction outside Kings Cross station where a cyclist died on 3 October.
Remodelling Ely North Junction will relieve a key bottle neck on the West Anglia main line enabling more cross country passengers and freight services, said Network Rail.