Hello Greg91, the highway modifications, from tertiary classification to residential, are based on a define set of characteristics that separates one from the other. There are different guidelines used to define highway classification, such as general OSM policy and RU Highways page (https://wiki.openstreetmap.org/wiki/RU:Highway_classification#Классификация_дорог_внутри_населенных_пунктов). Some of the highways, modified into tertiary roads, were left as is. Others were modified as residential because either they were small streets and alleys with residential buildings or highways largely surrounded by houses and less significant relative to other tertiary roads (https://www.openstreetmap.org/way/360172405, https://www.openstreetmap.org/way/412954283, https://www.openstreetmap.org/way/201715501, and https://www.openstreetmap.org/way/117979774). Some of the highways that were previously classified as service, but are publicly accessible, were then modified to the next appropriate classification (https://www.openstreetmap.org/way/189407283, https://www.openstreetmap.org/way/595593128). I personally feel that these changes were appropriate on those merits, and the idea that there wasn’t any other community concerns further justified the modifications. If you have any concerns, you are welcome to raise them and we can discuss them. I hope that answers your question.