## 4 Case Study
### Site Selection  
In this phase, data collection was mainly focused on site visits in Kwun Tong District, Hong Kong, in order to gather traffic information from real situations for further analysis. The detailed site visits were carried out on Shing Yip Street and Hing Yip Street, next to Hung To Road and a branch of Hoi Yuen Road in Kwun Tong District, which are the busiest roads in the area (as shown in Figure 10). The data collected included traffic facilities and information on the surroundings of the selected roads, such as the number of lamp posts, traffic lights and traffic lanes, together with distances and the lengths and widths of the roads. Data on traffic situations in the area considered were collected through observation, to obtain a better understanding of the real state of occupation and traffic congestion.  
Figure 9: Sample of survey questions for evaluating system performance.  
As a major industrial area, Kwun Tong District sees a large number of loading and unloading activities every day. Firstly, vehicles temporarily double-parked for loading or unloading or waiting for roadside spaces to become available, are common in the area of interest. Because a large number of trucks usually double-park on Hing Yip Street, serious traffic congestion can occur. Secondly, as parking spaces are scarce in Kwun Tong District, some nearby companies might occupy the roadside with objects such as traffic cones and boards, to preserve parking spaces. This situation hinders other road users from using the road. Therefore, in addition to detection, recognition and classification of various vehicles and objects, the computer vision-based roadside surveillance system needs to provide road users and logistics companies with information about occupancy and vacancy, so that they can optimize fleet schedules based on analytical information via self-regulation.  
External walls of buildings and lamp posts are the only possible positions for installing the HD vision devices for capturing images in the computer vision-based surveillance system. There is some difficulty in installing HD vision devices on the external walls of buildings, particularly on commercial buildings, without permission. It is believed that most property owners are likely to refuse to install the HD vision devices due to a lack of benefits and effects on the appearance of their buildings. Furthermore, various buildings may have different features at different heights, and this may lead to difficulties in unifying standards, such as the height of all HD vision devices, thus negatively affecting vision and possibly creating some overlaps. Therefore, lamp posts, managed by the Highways Department of the Hong Kong Government, are recommended as the best places to install the HD vision devices along roads and streets. In the areas considered, lamp posts have a mounting height of 10 m, set by the Highways Department [32]. The Highways Department is responsible for preventive and corrective maintenance of lamp posts. This is beneficial for the installation and operation of the vision devices and computer vision-based surveillance system, as breakdowns and errors can be resolved promptly to maintain a high level of stability in the system, compared with installations on the external walls of buildings.