PathSeg specifies a single transit path between two stops. The two stop IDs are available in the properties from and to and you can get further information about them on the Stations section of the response.
Table 1. PathSeg Type Attributes
Attribute
Always Included
Type
Description
id
Yes
ID
Indicates ID of the element. All PathSeg returned will have a unique ID.
It contains the real geometry of the transit line. When this element is not present, the real geometry is not available and the user can use the stops' location to draw a straight line.