So if I understood you correctly the only restriction restrictions are for traffic coming from the NW 21st Ave may not go straight on (in either direction). You need to add two turn restrictions: 1. Split the three ways at the two nodes. You will get seven ways after that. 2. Use the turn restrictions plugin (you may need to install it in JOSM) to add the first restriction: add the section of 21 Ave west of the intersection as 'from' add the southern part of the southbound Young Boulevard as 'to', add the western crossing node as via, chose the type 'only_right_turn' 3. Do the same for 21 Ave coming from the east. Have a look at the [turn restrictions wiki page][1] for reference. [1]: https://wiki.openstreetmap.org/wiki/Relation:restriction

So if I understood you correctly the only restriction are traffic coming from the NW 21st Ave may not go straight on (in either direction). You need to add two turn restrictions: 1. Split the three ways at the two nodes. You will get seven ways after that. 2. Use the turn restrictions plugin (you may need to install it in JOSM) to add the first restriction: add the section of 21 Ave west of the intersection as 'from' add the southern part of the southbound Young Boulevard as 'to', add the western crossing node as via, chose the type 'only_right_turn' 3. Do the same for 21 Ave coming from the east.