Before revision:  The improvement of runtimes with the Recursive-DBSCAN method is because of splitting the node-set into constituent clusters, which limits and decreases the number of possible solutions checked by the optimiser, consequently driving down the runtime .
After revision:  The improvement of runtimes with the Recursive-DBSCAN method is because of splitting the node-set into constituent clusters, which limits and decreases the number of possible solutions checked by the solver, consequently reducing the runtime. The proposed method consumes less memory and is able to find solutions for problems up to 5000 nodes, while the baseline Google Optimisation Tools solves problems up to 2000 nodes .