SimCity 4's 'Eternal Commuter Loop' Bug Finally Fixed After 23 Years

The Network Addon Mod, commonly called NAM, has long been the go-to overhaul for SimCity 4's transportation and infrastructure systems, combining key bug fixes with a broad set of extra build pieces such as overpasses, intersections, on-ramps, and roundabouts. The new version adds further improvements: adjacent elements can now be placed without the one-tile gap that was previously required, streets can be dragged diagonally, slope tolerances have been improved, and street networks can now include tunnels.

The headline fix, however, is for the Eternal Commuter Loop. The bug stems from regional pathfinding across city boundaries in certain layouts, causing Sims to bounce from location to location in search of work without ever taking a job. This wrecks zone demand, pushes traffic to unsustainable levels, and eventually collapses the economy. Until now, the only reliable workaround was to avoid building layouts that allowed commuters to loop between locations. Update 50 solves the problem by blocking specific neighbor-to-neighbor routes while letting the rest of the network run normally.

PCGamesN also highlights a major technical improvement: the mandatory implementation of a DLL has shrunk the NAM codebase by nearly 90%, or more than ten million lines, making the project easier to maintain and less prone to bugs. The update continues the project's long active life, which began barely a year after SimCity 4's debut.