Abstract
Infrastructure supporting vehicular network (V2X) capability is the key factor to the success of smart city because it enables many smart transportation services. In order to reduce the traffic congestion and improve the public transport efficiency, many intelligent transportation systems (ITS) need to be developed. In this paper, a smart traffic signal control (STSC) system is designed and implemented, it supports several smart city transportation applications including emergency vehicle signal preemption (EVSP), public transport signal priority (TSP), adaptive traffic signal control (ATSC), eco-driving supporting, and message broadcasting. The roadside unit (RSU) controller is the core of the proposed STSC system, where the system architecture, middleware, control algorithms, and peripheral modules are detailed discussed in this paper. It is compatible with existed traffic signal controller so that it can be fast and cost−effectively deployed. A new traffic signal scheme is specially designed for the EVSP scenario, it can inform all the drivers near the intersection regarding which direction the emergency vehicle (EV) is approaching, smoothing the traffic flow, and enhancing the safety. EVSP scenario and the related control algorithms are implemented in this work; integration test and field test are performed to demonstrate the STSC system.
Highlights
The population in the world has reached 7.7 billion in 2019, an increase of 1 billion since 2007, and the size of the global population would stand between 8.5 and 8.6 billions in 2030 [1]
An application layer, which is the pool of the application programs, supports six smart city applications including emergency vehicle signal preemption (EVSP), transit signal priority (TSP), eco-driving by signal plan broadcasting, roadwork and accident warning, pre-time signal control, and adaptive traffic signal control (ATSC)
It switches to ATSC mode (S2) when the roadside unit (RSU) has enough real-time traffic information collected from external data sources, a special designed adaptive traffic signal control algorithm will be responsible for the traffic flow control optimization in this mode
Summary
The population in the world has reached 7.7 billion in 2019, an increase of 1 billion since 2007, and the size of the global population would stand between 8.5 and 8.6 billions in 2030 [1]. The development of cooperative intelligent transportation systems, such as transit signal priority (TSP) for public transport, emergency vehicle signal preemption (EVSP), and adaptive traffic signal control (ATSC), is considered as the one of the important indexes in smart and sustainable cities Among these services, the key technology is Sensors 2020, 20, 508; doi:10.3390/s20020508 www.mdpi.com/journal/sensors. Three types of traffic control strategies are adopted including pre-time (predefined signal plan), actuated (triggered signal control), or ATSC (adaptive traffic signal control) depending on the traffic assignment strategy decided by traffic management authority These approaches do not fulfil the intelligent transportation systems requirements in the smart city, such as V2X-based applications proposed in a C-ITS project.
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