One of the five main demands used to measure the quality of cycling infrastructure (the others are safetydirectness, cohesion and attractiveness).

Comfort means little interaction with motor traffic, and limited noise or pollution. Cycle routes should also be easily navigable by all types of users, with good surfacing, good signage, and also understandable. Walking and cycling should be separated, to minimise potential conflict.  Cycling infrastructure comfort 

From 'Cycle Traffic and the Strategic Road Network' - 

Infrastructure shall meet design standards for alignment and surface quality, and cater for all types of user, including children and disabled people.