Highway pavement maintenance is very expensive not only in terms of costs to the responsible agencies but also in terms of disruptive delays to users. Construction and maintenance activities on four-lane highways (with two lanes in each direction) often require the closure of one of the two travel lanes. Longer work zones tend to increase the user delay costs. Maintenance work can be performed more efficiently, i.e., with fewer repeated setups, in longer zones. A relatively simple mathematical model is developed to optimize work zone lengths on four-lane highways where one lane in one direction at a time is closed. The objective is to minimize the total cost, including the agency cost, the accident cost, and the user delay cost. The optimized variable (e.g. work zone length) and the sensitivity results generated from a numerical example are presented in this study. With user-specified input parameters, this model can be used to optimize work zones on four-lane highways for a wide variety of circumstances.