The Green Cross Code is a brand created by the UK National Road Safety Committee (now the Royal Society for the Prevention of Accidents, RoSPA) to raise awareness of pedestrian road safety in the UK. The multimedia Green Cross Code campaign began in 1970 and continues today.
The Green Cross Code replaced the earlier Kerb Drill pedestrian safety campaign; the Kerb Drill’s military style (“Halt! Quick march!”) was deemed confusing to children by safety authorities.
Info gleaned from Wikipedia