==== MAPEM (MAP Extended Message) ====
MAPEMs describe the **topology of an intersection** (ETSI TS 103 301): the geometry of its lanes, which ingress and egress lanes exist, and which maneuvers connect them.

A MAPEM contains, among other things:
  - the reference position of the intersection
  - lane geometries (as offset points)
  - lane attributes (vehicle lane, bike lane, crosswalk, ...)
  - the allowed connections between lanes, referenced by signal groups

MAPEMs are sent by C-ITS traffic lights ([[en:c-its:rsu|RSUs]]). On their own they are mostly static — the dynamic signal states are transmitted separately via [[en:c-its:messages:spatem|SPATEM]]; both together enable use cases such as GLOSA (Green Light Optimal Speed Advisory).