The snake was about a kilometre closer to Granya Road than at the rock that was labelled "SLOW". The photo serves the purpose of reminding me of the approximate location. It was exactly where I stopped to find that my rear derailleur had broken. Since I couldn't pedal from there onwards I relied on gravity to travel. I was travelling fast past the snake and didn't stop to take a photo. But a friend returned to get a better look. The snake was between the "SLOW" sign and Granya road.
Thanks for clarifying that @clairesandford . It was most probably a Red-bellied Black Snake if it was relatively big and jet black in colour. Roughly how long was it?