The existing motor vehicle travel lanes are either narrowed to a single lane or diverted around the work zone, which may lead to disruptions in traffic flow due to reduced capacity. The capacity of the work zone can be estimated from research on the capacity associated with various lane closures on multilane facilities. The purpose of this study was to provide the Delaware Department of Transportation (DelDOT) with a review of the state-of-the-practice tools for managing work zone safety, estimating the traffic mobility impacts at work zones and developing Delaware-specific values much like those found in the DelDOT Work Zone Safety and Mobility Procedures and Guidelines and the 2010 HCM to represent work zone lane capacities on multilane signalized roadways. Since traffic flow on most of multilane signalized roadways in Delaware does not exceed the work zone capacity, it is more difficult to estimate true value of work zone capacity. To this end, we propose a new methodology to determine work zone capacity distribution based on the probabilistic speed-flow-density relationships. Data in terms of the traffic flow, speed, density, lane occupancy in work zones were collected in six work zones on freeways in California and twenty-five work zones on multilane signalized roadways in Delaware. The proposed methodology can be helpful in evaluating the variability of work zone capacity and selecting better the work zone traffic control strategies to improve the capacity and construction staging.