Consolidation carriers transport shipments that are small relative to trailer capacity. To be cost-effective, the carrier must consolidate shipments, which requires coordinating their paths in both space and time, i.e., the carrier must solve a Service Network Design problem. Most service network design models rely on discretization of time, i.e., instead of determining the exact time at which a dispatch should occur, the model determines a time interval during which a dispatch should occur. While the use of time discretization is widespread in service network design models, a fundamental question related to its use has never been answered: "Is it possible to produce an optimal continuous time solution without explicitly modeling each point in time?" We answer this question in the affirmative. We develop an iterative refinement algorithm using partially time-expanded networks that solves continuous time service network design problems. An extensive computational study demonstrates that the algorithm is not only of theoretical interest, but also performs well in practice. have long been supported by solving the so-called Service Network Design problem (Crainic 2000, Wieberneit 2008), which decides the paths for the shipments and the services (or resources) necessary to execute them. Service network design decisions for a consolidation carrier have both a geographic and temporal component, e.g., "dispatch a truck from Chicago, IL to Atlanta, GA at 9.05 pm." A common technique for modeling the temporal component is discretization; instead of deciding the exact time at which a dispatch should occur (e.g., 7.38 pm), the model decides a time interval during which the dispatch should occur (e.g., between 6pm and 8 pm).When discretizing time, service network design problems can be formulated on a time-expanded network Fulkerson 1958, 1962), in which a node encodes both a location and a time interval, and solutions prescribe dispatch time intervals for resources (trucks, drivers, etc.) and shipments. Service network design models calculate the costs for a set of dispatch decisions by estimating consolidation opportunities, i.e., by recognizing that prescribed dispatch time intervals for shipments allow travel together using the same resource. For example, shipments that should dispatch from the same origin node to the same destination node in the same dispatch time interval (say from Louisville, KY to Jackson, MI between 6 and 11 pm) are candidates for consolidation.Clearly, the granularity of the time discretization has an impact on the candidate consolidation opportunities identified. At the same time, the granularity of the time discretization also impacts the computational tractability. With an hourly discetization of a week-long planning horizon, 168 timed copies of a node representing a location will be created. With a 5-minute discretization of a week-long planning horizon, 2,016 timed copies of a node representing a location will be created.The latter discretization will likely yield a service network design prob...