Accessibility evaluation system for site layout planning – a tractor trailer example

Background Accessibility is a critical issue in site planning. A good accessibility plan can avoid possible conflicts involving equipment and allows for smooth transportation during the entire project. It can also ensure that sufficient space is available so that all onsite equipment, such as trucks, cranes and excavators can be safely operated. In current practice, the evaluation of accessibility is done manually, relying heavily on the experience of the construction planners. However, the evaluation needs to deal with temporal and spatial information simultaneously, which make the manual evaluations very challenging. Methods This research develops a sandbox environment for construction planners. As tractor-trailers are usually critical in accessibility evaluations, the simulation specifically focuses on these two-section vehicles. Four major steps were involved: Step 1: deriving a generic tractor-trailer mathematical model allowing real-time, physics-based computer simulation; Step 2: digitalizing a 2D site plan to the 3D virtual environment; Step 3: developing evaluation methods for accessibility, considering both safety and operability; Step 4: visualizing the evaluation results. We implemented these four steps using Microsoft XNA (a game platform) and Nvidia PhysX (a game engine). An example case is presented which uses the sandbox environment to evaluate the accessibility of a construction site. Results From the case study, we found that realistic visualizations and simulations provide solid references for construction planners. They are able to identify potential accessibility problems and unsafe situations in the sandbox environment and avoid them early on in the design and planning stages. Conclusion This paper proposed an innovative approach for evaluating accessibility during pre-construction site layout planning. It can present an intuitive and easily understood visualization result which clearly indicated the unsafe parts of the site layout plan.