Following the uMap link on the community forum discussion [1] I believe most of these streets do not have a weight restriction. The sign at the New Strangford Road/Tempest Road roundabout [2] shows the height/weight restrictions are 1 mile away, not immediately. The sign at the other end (East Cliff Road/Hill Crescent roundabout) is very hard to read unfortunately [3]. (Though it looks like the height restriction has been applied correctly in the next changeset)

[1] https://community.openstreetmap.org/t/optimoroute-organised-editing-activity-in-the-uk-truck-hgv-access/129894
[2] https://www.bing.com/maps?toWww=1&cp=54.836737%7E-1.343713&lvl=16.1&mo=om.1&pi=0.4&style=x&dir=134.4
[3] https://www.bing.com/maps?toWww=1&cp=54.826934%7E-1.325414&lvl=16.1&mo=om.1&pi=0.8&style=x&dir=312