adding multiple points to a linestring in PostGIS

How about

select st_union(t1.wkb_geometry) as wkb_geometry into some_table from 
(
    select wkb_geometry from r_lines  union select wkb_geometry from a_lines
) t1

then viewing the result of some_table

The query above unions all your lines in r_lines and all your lines in a_lines into one result, then merges all of that together in one line and writes this to table some_table. If you need to then split this again, splitting at every intersection, we can explode this table using the query

select (st_dump(wkb_geometry)).geom as wkb_geometry into some_split_table from some_table

The output from above can be seen in some_split_table