Spatial Objects must be large enough so that Entities cannot step right over them and thereby avoid being affected or filtered by the object. The exception to this rule is that Exits and Level Exits always recognise and affect Entities that step over them.

The longest single step that an Entity can take is calculated from the distance the Entity can travel in one time-step (0.6 seconds) going at the fastest unimpeded speed according to the Speed Distribution of the Entity Type it belongs to. At its top speed (1.7 m/s), the Default Entity Type can take a step of 1.02 metres.

This implies that any Spatial Objects intended to affect a Default Entity Type should have a depth greater than 1.02 metres in the direction of the Entities’ approach to ensure that they are not stepped over; again, with the exception of Exits and Level Exits.