Comparison of Traffic Signal Control in some Large Cities

Due to increasing urbanization and population growth, the number of large cities and megacities increases dramatically, mainly in developing countries. Traffic signals are the most widely used measure to control traffic flow in urban networks on an operational level. As much as the number of controllers is increasing, the complexity of suitable control techniques grows. Today, a wide range of signal control systems are developed and implemented around the world. Many studies on traffic signals focus on capacity increase and delay minimization but little is known how the systems compare to each other. This paper reports the results of a purpose-developed questionnaire which was distributed to transportations authorities of developing as well as of developed larger cities. 19 cities responded in detail. Within the arena of ITS the term of intelligent signal control is differently used. This paper tries to establish a common terminology on fixed time, traffic responsive, actuated and adaptive signal control in a comprehensive way in order to compare and accredit the different systems in a proper way. Although much is published on different kinds of traffic responsive signal control systems current practise in many developing countries indicates that fixed time signal control is still widely used due to cost and low requirements on expertise. Thus this paper raises the question whether current advanced systems are either too costly or do not serve its purpose in order to be applied more widely.