The main purpose of highway maintenance is to ensure safe and convenient movement of people and goods on highway networks. The functioning, well maintained highway network spans urban areas and is instrumental in creation of added value in Switzerland. However, maintenance actions can cause traffic congestion with considerable negative impact on road users and thus inducing societal costs. Recognising this issue a highway agency strives to minimise both agency and society costs by methodic planning of highway work zones.
The objective of this research is the development of a method to determine optimal highway work zones for a road segment. The optimal work zone is understood to minimise overall costs within a time period, i. e. agency costs based on live-cycle cost analysis and the costs due to detrimental impact of maintenance activities on road users and environment. Furthermore the potential and limits of the proposed method are identified by applying it to two real world examples on the Swiss highway network.
Both the conservation measures as well as their interventions and impact on the traffic flow are quantified monetarily.
The situation of the transport system is generally modeled as a schematic network. The individual objects (road sections, engineering structures, technical facilities and equipment) are in terms of coordinates (linear) via kilometer distances related to each other. The object is defined as a distance between two points on the network.
The derivation of the economically optimal construction site (follow measures and implementation time points) requires the evaluation of all possible variants of types of measures / implementation times for the lowest total cost.
This research project enhances Hajdin’s method for planning of optimum highway work zones by introducing further constraints and parameter and adapting it to cope with complex real world problems in highway maintenance management. The result is a three step method for planning optimum highway work zones based on graph theory. First step defines the network model as a directed graph based on the topology of the highway network and the time and scope of maintenance actions.
The structure of graphs published in final report enables the consideration of different traffic regimes for work zone evaluation. For this purpose the existing median openings of the divided highway are considered and the influence of lanes crossover to the opposite traffic direction is modeled. Additionally the planning horizon was extended to two years divided in four time periods.
The second step includes the development of the cost model comprising agency costs, user costs and costs due to environmental impact. These costs are assigned to edges and nodes of the graph representing highway network. By the virtue of network model and cost model both object oriented and work zone oriented costs can be adequately considered.
In the third step the optimum work zones are determined, which corresponds to the minimum cost path in the directed graph under given constraints. For this purpose a binary linear program is solved using the traditional branch-and-bound-method.
This three step method for planning optimum highway work zones could be successfully tested on two real world work zones. The model containing network definition as a directed graph and cost model considering agency, road user and environment was easily adaptable to the test work zones. The proposed model enables in addition to different intervention types the consideration of traffic regime in the work zone including crossovers through existing median openings. This makes the model very flexible and enables its application to larger parts of the highway network or secondary road networks. The application of this model to the entire highway networks depends on the computational time required to perform optimisation. The cost model includes all relevant costs i. e. the ones related to the agency, road user and environment.
The practical application of the proposed method is somewhat hampered by the uncertain unit costs (e. g. setup costs for traffic regime). Further research on this part is necessary. In present research
A new method to determine optimal highway work zones for a road segment was developed.
The project will help to save public sources by highway reconstructions.