# Simulation Study on an ICT-Based Maritime Management and Safety Framework for Movable Bridges
## 3 System Considerations  
The entire maritime automation and security system is pivoted on the basis of an imaginary belt division system. The Alert belt and the Emergency Belt are two virtual belts that are considered on both sides of the bridge at a specified distance. Based on the origin and destination movement of the ship, the Alert Belt and Emergency Belt are named sequentially entry Alert Belt, entry Emergency Belt, exit Emergency Belt and exit Alert Belt. Another distance based on the DSRC range is also considered for the buoy placement,  
Figure 2: Components of the typical camera-based sensor integrated self-powered buoy for the proposed system. from which data will be connected for further investigation. The direction of two different routes is shown in Figure 3 using arrow indications. For design consideration, four fixed buoys are installed at each of the two ship routes. The purpose of these being to detecting ships' positions. The buoy has been named according to the following considerations. For direction A to B,  
The buoy at entry Alert Belt = _Baa_  
The buoy at DSRC range = _Ba_  
The buoy at entry Emergency Belt = _Bae_  
The buoy at exit Emergency Belt = _Bbe_  
For direction C to D,  
The buoy at entry Alert Belt = _Bca_  
The buoy at DSRC range = _Bc_  
The buoy at entry Emergency Belt = _Bce_  
The buoy at exit Emergency Belt = _Bde_  
The distance of the Alert Belt from each side of the bridge has been determined by the bridge length and how much time is needed for evacuating the bridge off of the on-bridge traffic. When ships enter the Alert Belt from any route, the traffic signal turns yellow, followed by red light in a safe interval. The bridge evacuation system is maintained by a counting algorithm and a camera-detection system. The time for bridge evacuation, \(T_{bv}\) has been calculated by considering the average speed of the on-bridge traffic, \(V_{bu}\), and the length of the movable part of the bridge, \(D_{fl}\) using Equations (1) and (2). \[T_{bv}=\frac{D_{fl}}{V_{bva}}, \tag{1}\]  
\[V_{bva}=\frac{\text{Sum of the velocities of the vehicles inside the movable part of the bridge}}{\text{Total number of the vehicles inside the movable part of the bridge}}. \tag{2}\]  
A setup of four speed cameras is considered separately on both entry and exit lanes of the bridge to ensure the counting and velocity detection of each vehicle in entry and pass. The installment of the speed camera system is illustrated in Figure 4.  
Figure 3: Illustration of the complete system and installments with specific legends. For bridge vehicle traffic route AB,  
Assigned camera for entry lanes = \(Ca\)  
Assigned camera for exit lanes = \(Cb\)  
For bridge vehicle traffic route CD,  
Assigned camera for entry lanes = \(Cc\)  
Assigned camera for exit lanes = \(Cd\)  
When vehicles enter through bridge entry lanes, they are counted, and their velocities are being recorded. At the same time, each vehicle that passes through the exit lanes of the bridge is classified by cameras at the exit lanes. The number of vehicles on the bridge is then the difference of the aggregated count between entry and exit lane cameras. If the number of vehicles is found to be 0, the bridge is empty and is ready to be opened. This procedure has been coined as bridge evacuation. Consequently, the algorithm used to achieve this has been named the counting algorithm for bridge evacuation. When ships are detected by buoys \(Baa\) or \(Bca\), the evacuation is initiated to make the bridge clear out the vehicles and open to allow the passing of the ships. The total time required for preparing ship route through the bridge is given as  
\[T_{i}=T_{b}+T_{by}, \tag{3}\]  
Figure 4: The camera setups for bridge traffic control system. where \(T_{b}\) refers to the time required for bridge opening or, closing. Similarly, the minimum required distance between the Alert belt and DSRC range is expressed as  
\[D_{altz}=V_{bsh}*T_{t}, \tag{4}\]  
where \(V_{bsh}\) is the assigned highest speed limit for ships at the bridge maritime zone.