“…According to the review conducted by Zhu, Fu, and Ma (), studies on network sensor location can be categorized into studies on flow‐observability‐oriented sensor location, studies on flow‐estimation‐oriented sensor location, and those on travel‐time‐estimation‐oriented sensor location. Here, the network sensor location problem belongs to the facility location problem, such as the location problem of freight facility (Hajibabai, Bai, & Ouyang, ; Xie & Ouyang, ), railroad wayside defect detection (Ouyang, Li, Barkan, Kawprasert, & Lai, ), and recharge facility for electric vehicles (Zhang, Rey, & Waller, ), in operations research area. The flow‐observability‐oriented sensor location aims to determine how many sensors are needed as well as where they should be located for the unique determination of the unobserved link flows.…”