Study On The Optimizing Highway Work Zone Layout

With the rapid increasing of highway mileage,the amount of motor vehicle and motor vehicle driverincrease dramatically，which bring a serious challenge to traffic safety. After being opened to traffic,highway and its supporting facilities become aging and damaged with increasing of the traffic load andprocessing of service operating time, so it needs maintenance or reconstruction.At the same time, the agehas come when some highways that were constructed earlier are being maintained or reconstructed insuccession, as they have been begun to reached saturated traffic and appeared traffic congestion before thedesigned service life,and more and more highways need alteration and reconstruction。Therefore, highwayconstruction and maintenance work zones will be more and more.As an important part of highway trafficsystem,work zone is given space of spot for construction and maintenance. Work zone layout and setupparameters directly influence traffic flow conditions, the safety of road users and construction workers.In view of the highway construction and maintenance work zone layout, this paper design thequestionnaire.The survey on work zone practices was designed to gather information on the impact of61work zone parameters that are grouped in11divisions on the risk of crash occurrence.The study focuses onidentifying potential work zone parameters that impact work zone crash occurrence,and estimating theprobability of work zones to encounter severe crashes.Then this study presents a new metric for calculatingwork zone crash costs based work zone layout parameters to estimat the monetary value of work zonecrashes.On the basis of above discussion, a novel optimization model is developed for work zone setup ofhighway construction projects.The optimal work zone setup model is formulated to identify the optimalsetup of construction or maintenance work zones in order to minimize their total costs,including crash cost,construction cost and user delay cost.Considering that traffic volume changes dynamically over time，themodel is designed to find an optimal solution for five main work zone decision variables: work zonesegment length, work zone speed limit, starting time, type of TTC, and barrier type.This model not onlyconsider the impact of work zone speed limit, highway free flow speed, and type of construction activity onwork zone capacity,but also consider the traffic risks caused by work zones and the combined impact oftheir setup parameters on the probability of crash occurrence,and the impact of the total project length onthe optimization procedure.Finally, the optimization model was implemented using genetic algorithms (GAs) in Matlab2012a.Asingle-objective GeneticAlgorithm (GA) module is incorporated in the optimization model to solve thismixed real-integer cost optimization problem. The minimum total work zone cost was attained for anoptimum work zone setup with different operation starting times.