Any failure or disruption in traffic flow can propagate through the road network. However, the server of such disruption and its consequences depends on the robustness and resiliency of transportation systems. In this...Any failure or disruption in traffic flow can propagate through the road network. However, the server of such disruption and its consequences depends on the robustness and resiliency of transportation systems. In this context, traffic management (TM) measures will help the traffic stream to prevent the occurrence of such conditions or recover faster after experiencing the disruption. The main objective of this paper was to elaborate the contribution of TM measures to the resiliency of transportation systems, as well as, their vulnerability against external threats. Furthermore, a concept design for variable message signs (VMS) is developed and evaluated in terms of contribution to the resiliency of road networks. As well, new vulnerabilities associated with the implementation of VMS are investigated. The result of this study pointed out that ramp-metering, variable message signs, variable speed limits, and autonomous vehicles are valuable tools to mitigate the severity of traffic disruptions. VMS is one of the most effective approaches that enhance traffic resiliency by reducing traffic inflow to congested areas. However, these measures have opened new vulnerabilities to threats, especially cyber-attacks. Several cases of VMS hacks have occurred in the world and provided false messages to road users. It gets even worse with using an integrated wireless communication interface. Therefore, it is necessary to consider the security of such systems in advance, before practical application.展开更多
The variable message signs (VMS) have been widely used in guiding and managing the dynamic traffic with development of intelligent transportation technologies. It is known that cell transmission model (CTM) can well r...The variable message signs (VMS) have been widely used in guiding and managing the dynamic traffic with development of intelligent transportation technologies. It is known that cell transmission model (CTM) can well reproduce such traffic dynamics as shock waves and jams. This paper presents a new method to estimate the route travel times by using the CTM in conjunction with a logit-based route choice rule. The impacts of VMS on a two-route scenario with recurrent and non-recurrent traffic congestion are numerically investigated by analyzing the changes of route flow and travel time. Simulation results show that in networks with suitable long links, the VMS can positively influence travelers' decision making so as to improve the system performance. For non-recurrent congestion, the value space of the route choice parameter that affects the flow distribution between two routes is narrower in the case of high traffic demand than that in the low demand case.展开更多
This paper reviews the effectiveness of vehicle activated signs. Vehicle activated signs are being reportedly used in recent years to display dynamic information to road users on an individual basis in order to give a...This paper reviews the effectiveness of vehicle activated signs. Vehicle activated signs are being reportedly used in recent years to display dynamic information to road users on an individual basis in order to give a warning or inform about a specific event. Vehicle activated signs are triggered individually by vehicles when a certain criteria is met. An example of such criteria is to trigger a speed limit sign when the driver exceeds a pre-set threshold speed. The preset threshold is usually set to a constant value which is often equal, or relative, to the speed limit on a particular road segment. This review examines in detail the basis for the configuration of the existing sign types in previous studies and explores the relation between the configuration of the sign and their impact on driver behavior and sign efficiency. Most of previous studies show that these signs have significant impact on driver behavior, traffic safety and traffic efficincy. In most cases the signs deployed have yielded reductions in mean speeds, in speed variation and in longer head-ways. However most experiments reported within the area were performed with the signs set to a certain static configuration within applicable conditions. Since some of the aforementioned factors are dynamic in nature, it is felt that the configurations of these signs were thus not carefully considered by previous researchers and there is no clear statement in the previous studies describing the relationship between the trigger value and its consequences under different conditions. Bearing in mind that different designs of vehicle activated signs can give a different impact under certain conditions of road, traffic and weather conditions the current work suggests that variable speed thresholds should be considered instead.展开更多
文摘Any failure or disruption in traffic flow can propagate through the road network. However, the server of such disruption and its consequences depends on the robustness and resiliency of transportation systems. In this context, traffic management (TM) measures will help the traffic stream to prevent the occurrence of such conditions or recover faster after experiencing the disruption. The main objective of this paper was to elaborate the contribution of TM measures to the resiliency of transportation systems, as well as, their vulnerability against external threats. Furthermore, a concept design for variable message signs (VMS) is developed and evaluated in terms of contribution to the resiliency of road networks. As well, new vulnerabilities associated with the implementation of VMS are investigated. The result of this study pointed out that ramp-metering, variable message signs, variable speed limits, and autonomous vehicles are valuable tools to mitigate the severity of traffic disruptions. VMS is one of the most effective approaches that enhance traffic resiliency by reducing traffic inflow to congested areas. However, these measures have opened new vulnerabilities to threats, especially cyber-attacks. Several cases of VMS hacks have occurred in the world and provided false messages to road users. It gets even worse with using an integrated wireless communication interface. Therefore, it is necessary to consider the security of such systems in advance, before practical application.
基金Supported by the National Basic Research Program of China (Grant No.2006CB705503)the National Natural Science Foundation of China (Grant No.70521001)the Doctoral Fund of Beijing Municipal Science and Technology Commission (Grant No.ZZ0737)
文摘The variable message signs (VMS) have been widely used in guiding and managing the dynamic traffic with development of intelligent transportation technologies. It is known that cell transmission model (CTM) can well reproduce such traffic dynamics as shock waves and jams. This paper presents a new method to estimate the route travel times by using the CTM in conjunction with a logit-based route choice rule. The impacts of VMS on a two-route scenario with recurrent and non-recurrent traffic congestion are numerically investigated by analyzing the changes of route flow and travel time. Simulation results show that in networks with suitable long links, the VMS can positively influence travelers' decision making so as to improve the system performance. For non-recurrent congestion, the value space of the route choice parameter that affects the flow distribution between two routes is narrower in the case of high traffic demand than that in the low demand case.
文摘This paper reviews the effectiveness of vehicle activated signs. Vehicle activated signs are being reportedly used in recent years to display dynamic information to road users on an individual basis in order to give a warning or inform about a specific event. Vehicle activated signs are triggered individually by vehicles when a certain criteria is met. An example of such criteria is to trigger a speed limit sign when the driver exceeds a pre-set threshold speed. The preset threshold is usually set to a constant value which is often equal, or relative, to the speed limit on a particular road segment. This review examines in detail the basis for the configuration of the existing sign types in previous studies and explores the relation between the configuration of the sign and their impact on driver behavior and sign efficiency. Most of previous studies show that these signs have significant impact on driver behavior, traffic safety and traffic efficincy. In most cases the signs deployed have yielded reductions in mean speeds, in speed variation and in longer head-ways. However most experiments reported within the area were performed with the signs set to a certain static configuration within applicable conditions. Since some of the aforementioned factors are dynamic in nature, it is felt that the configurations of these signs were thus not carefully considered by previous researchers and there is no clear statement in the previous studies describing the relationship between the trigger value and its consequences under different conditions. Bearing in mind that different designs of vehicle activated signs can give a different impact under certain conditions of road, traffic and weather conditions the current work suggests that variable speed thresholds should be considered instead.
