Tower cranes, serving as the primary vertical and horizontal transportation tools in construction, are essential to building processes. But how effectively are tower cranes being used in an environment where even a one-day delay in construction can cost thousands of dollars? Some studies show that crane operators have idle time for up to 55% of their working hours[1][2] In an 8-hour shift, this equates to 4 hours 24 minutes of non-productive time.  With the great motivation to utilise this idle time and to make the operator actions more productive, we designed a Unity-based simulation that tested the feasibility of one operator controlling multiple cranes simultaneously. The core of our project involved a game-like scenario experimented in Unity through Virtual Reality. Our VR experiment in Unity aimed to demonstrate the practicality and potential advantages or disadvantages of multi-crane operation. We aimed to transform the construction industry and make it more productive by converting idle times to new tasks of crane operators. The result could reshape the role of crane operators, making the construction process more streamlined and effective. 

The development was carried out using Unity 3D Game Engine, which allowed us to integrate model assets for tower cranes and various construction materials. The assembly logic of the tower crane parts was meticulously followed to ensure realism in the simulation environment. For the interaction logic, we utilized C# scripts to define the functionalities of each crane component, as well as the functions of specific materials to be transported. Additionally, an Oculus VR camera was integrated into the scene, enhancing the operator's immersive experience. The VR controllers are programmed with various functions, for instance teleportation between cranes and control of crane operations. The simulation tasks were designed to be diverse, challenging the operator to complete specific tasks for each crane. Upon completion, the simulator recorded the time spent on each task, exporting the data to an Excel sheet for analysis. This setup aims to assess the efficiency and practicality of multi-crane operation by a single individual. 

In our simulation, we aimed to find out how many cranes together are the most effective choice by comparing multi-crane operations with existing single-crane comparisons, not just focusing on task completion times, but also on the operator's ability to remember and follow tasks. Initially, managing two cranes simultaneously proved straightforward and efficient, completing three tasks in 120 seconds with full comfort. However, when simulating three cranes, task management became challenging, leading to a slight increase in time (130 seconds for three tasks) and reduced comfort. This complexity was due to the difficulty in task recall when switching cranes. Lastly, the attempt with four cranes further escalated these challenges (especially following task flow), resulting in a total time that is close to current standards for a single crane operation. 

Our findings suggest an optimal limit for multi-crane operation by one operator, highlighting a balance between operational efficiency and task complexity. While the dual crane operation proved effective, increasing to three or four cranes introduced significant challenges in task management and memory load. Despite these limitations, the simulation underscores current constraints in operating multiple cranes simultaneously using Virtual Reality. Yet, as construction sites become smarter but demand for being operator decreases, the potential for one person to efficiently manage multiple cranes with advanced Mixed Reality technology is becoming increasingly feasible, paving the way for more efficient and smarter site operations in the future.

[1] T. Danel, Z. Lafhaj, A. Puppala, S. Lienard, P. Richard, “Proposal for Tower Crane Productivity Indicators Based on Data Analysis in the Era of Construction 4.0. Buildings,” 2021, 11, 21. 

[2] D. Lee, K. Son, and S. Kim, “Analysis of operation efficiency of tower crane in form work construction for multi-family housing,” (accessed Jan. 18, 2024).

[3] Tarhini, H., Maddah, B., & Hamzeh, F. (2020). The traveling salesman puts-on a hard hat –Tower crane scheduling in construction projects. European Journal of Operational Research, 328-338. https://doi.org/10.1016/j.ejor.2020.10.029