## 5 Application of Self-Sensing Materials for
### Traffic Monitoring  
The maneuvering of overloaded vehicles is a major cause of premature pavement degradation. To this end, weigh in motion (WIM) should be utilized for controlling the weight of the vehicles in real time. To date, various types of WIM types have been employed. However, the high cost of the current technologies of WIM is one of the big challenges for road management authorities. To tackle this, recently, the multifunctional cementitious composites containing conductive fillers have gained attention for application in WIM to control the weight of the vehicles in real time and consequently enforce the weight regulation. Inadequate traffic management systems contribute to traffic accidents, leading to fatalities and injuries. For example, in the first half of 2021, the United States reported 20,160 fatalities due to traffic accidents [224]. Consequently, WIM systems, along with real-time and continuous traffic monitoring (including axle load detection, speed calculation, and vehicle spacing), are crucial for an intelligent traffic management system [225]. Overloaded trucks, for instance, are a major concern for authorities as they can lead to premature road failure, reduced pavement service life, and increased traffic accidents [226]. Monitoring the weight of passing trucks and overloaded heavy vehicles is essential, making WIM systems highly important. To this end, various sensor types including in-road, on-road, and over-road sensors have been extensively employed for traffic monitoring [227]. Up to  
Figure 22: Application of electrical conductive cementitious composites. now, a range of detectors such as electronic, magnetic, video, optical, and acoustic sensors have been implemented [228]. However, conventional sensors face drawbacks such as incompatibility with road pavement and railway tracks, high costs, excessive maintenance needs, and vulnerability to harsh climatic conditions [201]. To address these challenges, the intrinsic self-sensing feature of multifunctional cementitious composites can be employed for traffic monitoring, as seen in Figure 23 [92]. Figure 23 illustrates the development of self-sensing cementitious composites from laboratory research to field application [229]. As shown in Figure 23e,d, these composites are capable of easily detecting human movement and passing vehicles. However, the self-sensing cementitious composites require optimization in the laboratory before being applied to real-world projects in the field. In another study, [PERSON] et al. [230] explored the feasibility of using a self-sensing cementitious composite containing nickel particles for detecting traffic flow. The study's results demonstrated that embedded self-sensing cementitious sensors with nickel particles in road pavement are capable of detecting passing vehicle axles. While environmental factors such as moisture and temperature can alter the pattern of recorded electrical signals, the authors noted that the effects of moisture and temperature are continuous and gradual and do not significantly impact the abrupt change in electrical signals caused by vehicle passage [231]. The effectiveness of self-sensing pavement, produced by incorporating CFs for weight in motion WIM applications, has been assessed in field conditions [232]. The signals  
Figure 23: Application of self-sensing cementitious composites for pedestrian and traffic detection: (**a**) development stage in the lab; (**b**) human motion test; (**c**) traffic flow test; (**d**) detection of human motion; (**e**) traffic detection [229], published by Elsevier (2022). recorded during the passage of unloaded and loaded five-axle trucks were analyzed. It was found that the CF-based self-sensing pavement is capable of detecting axle loads. It was also found that the FCR under an unloaded truck is less pronounced than that under a loaded truck, indicating the self-sensing pavement's ability to determine the level of axle load.