On January 26, 2016 I sent this note to the office of our City of Ottawa councillor, David Chernushenko:

Our condo is across from the Smyth OC Transpo station. Many pedestrians walk to the station at all hours. There is a sidewalk only on our side of Riverside Drive and many of the pedestrians walk on the street to the station on the other side. This presents a hazard with vehicle traffic, especially at night and in winter when the street is narrowed.

I received this reply:

“This section of Riverside Drive is classified as a Local roadway, and provides direct access to transit, so qualifies for a sidewalk.  A sidewalk is provided, along the east side of the road where the land use destinations and points of origin are situated.  This satisfies the Council approved policy for sidewalks on this type of roadway.  Any opportunity to consider implementing a second sidewalk on the west side would be at the time of future road reconstruction on this segment or redevelopment of the surrounding lands, if any.”

In short, once this road is scheduled for reconstruction another sidewalk will be considered.
The same criteria exists for all existing infrastructure, like in Heron Park for instance.