# Efficient Intersection Management Based on an Adaptive Fuzzy-Logic Traffic Signal
## 2 Related Work
### Traffic-Actuated Controllers  
In contrast to pre-timed control, traffic-actuated control can extend or terminate signal phases in response to vehicle actuation, which is detected by on-road sensors [51]. An actuated control is typically used for isolated intersections where the traffic signal control operates independently of any other traffic signal [52]. Generally, three parameters are required for this type of control: (1) the minimum green time, (2) the vehicle extension time (a.k.a., passage time), and (3) the maximum green time. Regardless of the traffic demand, green time is configured for at least a specified minimum duration. Then, by detecting whether a queue has been cleared or the gap between vehicles has increased, the green time is terminated. Additional extensions to the green interval can be applied until reaching the maximum green time.  
While early actuated controllers were based on prefixed settings, most recent approaches have been focused on integrating an adaptive behavior by including methods to dynamically adjust the controller's parameters.  
[PERSON] et al. [53; 54] have proposed methods to determine optimal timing parameters by estimating future traffic demands. Hence, through a periodic optimization of such parameters, the controller's timing settings are dynamically updated. To achieve this, they formulated prediction algorithms to estimate the future arrival flow rate for each signal phase based on the available signal-timing data obtained from previous cycles.  
[PERSON] and [PERSON] proposed a delay-time actuated traffic controller [43] which was designed to adjust the green times according to the vehicles' delay times. In this sense, they stated that a delay occurs when the vehicle's current speed is below a maximum achievable speed. Assuming that delays are captured, the controller extends the green intervals in such a way that a vehicle's platoon can cross the intersection, dissolving the queue. Otherwise, the green interval is interrupted. Therefore, the green intervals are bounded by the delay values. Their objective was to minimize delay times for users of motorized vehicles by allocating green times in a preferably efficient way. To measure the delay, this proposal suggested the use of video processing techniques, probe vehicle data as well as vehicle infrastructure integration.  
By leveraging vehicle-to-infrastructure (V2X) communication [55; 56], [PERSON] et al. [44] proposed to improve the delay-time actuated traffic signal by integrating the Green Light Optimized Speed Advisory (GLOSA) application [57]. In addition to minimizing delay times, this approach gave speed recommendations to drivers based on the oncoming switching times. In this way, the controller outperforms the classic traffic actuated controllers by improving the vehicle's motion and signal switching.  
[PERSON] and [PERSON] [58] proposed dynamically determining the maximum green times through a fuzzy control. They considered three inputs: (1) the maximum length of queues behind the red intervals, (2) the maximum queue length behind the green intervals, and (3) the arrival flow rate approaching green intervals. By considering these inputs, the system established the maximum green times to prevent long vehicle delays behind the red intervals, clear the queues, and serve the arrivals at the end of the green interval. The signal timing was adjusted by considering a time interval between the minimum and the maximum green time. Thus, each green interval was started with a specified minimum time, one second prior to the end, whilst the phase is extended according to the maximum extension determined by the fuzzy system. This proposal outperforms the traditional traffic actuated control method by automatically adjusting maximum green times for different timing plans of the day, avoiding the requirement of providing maximum green times for different times of the day.