What restricted the operational flexibility of early refrigerated rail cars that used ice bunkers?

The need for constant monitoring and replenishment of ice at fixed stations

While refrigerated rail cars marked a significant improvement over previous transport methods, their operational flexibility was still substantially curtailed by their reliance on external cooling resources. These early cars, often called 'reefers,' depended on ice packed into bunkers. For long-haul routes, this necessitated that the route planning include specific stations equipped solely for the purpose of monitoring the ice levels and replenishing them. This dependence on fixed, fixed infrastructure meant that the cooling power was not truly mobile, restricting logistical routes and increasing transit overhead compared to later, self-powered units.