QuickZone Improvement for Rural Freeway and Model Validation

This review indicated that in QuickZone 2.0 a deterministic queuing model is applied to calculate the delays for oversaturated conditions; stochastic and speed reduction delays were not included. Data collected from rural freeways in Mississippi show that saturated and oversaturated traffic flow may not occur in work zones. For situations like this, the delay components that are not included in QuickZone are significant. The current delay model of QuickZone needs improvement. This paper describes a model improvement made to QuickZone. The improvement considers delays from the deceleration before a work zone, slow-moving traffic along the work zone, acceleration after the work zone, and stochastic delays within the work zone area. The Excel Visual Basic Application implementation of the model in QuickZone is discussed in this paper. Traffic flow parameters such as speed and volume of more than 10 work zones in the rural area of Mississippi were collected to verify the newly improved QuickZone in undersaturated conditions; CORSIM, traffic simulation software sponsored by FHWA, was utilized to compare the delay from the improved QuickZone for the work zones in oversaturated conditions. Verification results from the numerical examples showed that the improved QuickZone provided more reasonable delay estimations than the original version did, especially for rural work zones in under-saturated conditions. Therefore, the improved QuickZone can capture the delays in undersaturated and oversaturated conditions.