According to the Royal National Institute for the Blind, here are the explanations of the bumps and markings which denote 'tactile' pavements
• There are different patterns for different messages - not just generic bumps
• Dots in a grid mean a dropped curb for crossing the road
• Offset dots, i.e. not aligned, mean there’s a train platform and possibly a gap!
• Lozenges mean that there’s a tram crossing
• Horizontal stripes mean there are stairs or an obstacle ahead of you but vertical stripes mean a safe path to follow
• The pavement can be colour coded - for example, bright contrasting colours help partially sighted people to understand if they’re at a traffic lights crossing