Generalizing the probability of reaching a destination in case of route blockage

When road blockages occur owing to disasters or congestion, traffic is unable to pass, paralyzing urban functions. Though previous studies have analyzed road blockages in specific cities, a more general approach valid for a wide range of road networks is required. In this study, different blockage rates were applied to three square lattice sizes as well as square, triangular, and hexagonal lattice configurations to simulate an assortment of road network geometries, and agent-based modeling was applied to quantitatively evaluate the resulting arrival probabilities and travel times. The results did not change significantly with the blockage rate, regardless of lattice size. For the square lattice, the route from the starting point to the destination point was secured when the blockage rate was ≤30%, but the probability of not arriving at the destination point increased considerably when the blockage rate was >30% and reached an infinitesimally small value when the blockage rate was >60%. When fewer routes connected the lattice intersections, the destination was more likely to be unreachable, even for a low blockage rate. These results were then validated by percolation theory, demonstrating an effective basis for travel feasibility evaluations when an urban road network is blocked.