Topic
Speed limit
About: Speed limit is a research topic. Over the lifetime, 4321 publications have been published within this topic receiving 53114 citations. The topic is also known as: speed limits & road speed limit.
Papers published on a yearly basis
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Papers
TL;DR: In this paper, the optimal coordination of variable speed limits and ramp metering in a freeway traffic network is discussed, where the objective of the control is to minimize the total time that vehicles spend in the network.
Abstract: This paper discusses the optimal coordination of variable speed limits and ramp metering in a freeway traffic network, where the objective of the control is to minimize the total time that vehicles spend in the network. Coordinated freeway traffic control is a new development where the control problem is to find the combination of control measures that results in the best network performance. This problem is solved by model predictive control, where the macroscopic traffic flow model METANET is used as the prediction model. We extend this model with a model for dynamic speed limits and for main-stream origins. This approach results in a predictive coordinated control approach where variable speed limits can prevent a traffic breakdown and maintain a higher outflow even when ramp metering is unable to prevent congestion (e.g., because of an on-ramp queue constraint). The use of dynamic speed limits significantly reduces congestion and results in a lower total time spent. Since the primary effect of the speed limits is the limitation of the main-stream flow, a comparison is made with the case where the speed limits are replaced by main-stream metering. The resulting performances are comparable. Since the range of flows that main-stream metering and dynamic speed limits can control is different, the choice between the two should be primarily based on the traffic demands.
662 citations
Dissertation•
1 Jan 2004
TL;DR: The power model, which estimates the relationship between speed and safety, is not a new tool as the model has been used both in theory and pracise in several countries for many years and is tested and validated im a cross-sectional study and shows that the power model is valid with regard to injury accidents, fatal accidents and the number of injured but not for theNumber of fatalities.
Abstract: Traffic safety work needs different methods and tools in order to choose and evsaluate traffic safety measures. The thesis contributes to this problem by presenting and visualizing a method which describes the traffic safety situation in several dimensions. The method used to describe the traffic safety problem shows the potential of a simultanous presentation and evaluation of these dimensions and demonstrates that the method can be expanded to several dimensions or ratios estimating the exposure, the risk and the consequence. This is illustrated in describing the traffic safety situation for different road user groups and age groups. The power model, which estimates the relationship between speed and safety, is not a new tool as the model has been used both in theory and pracise in several countries for many years. In the thesis the theoretical and practical background are presented. The power model is here also tested and validated im a cross-sectional study. These analyses show that the power model is valid with regard to injury accidents, fatal accidents and the number of injured but not for the number of fatalities. The power model underestimates the effect on fatalities. (Less)
524 citations
TL;DR: The study suggests that the analysis of the environmental impacts of any traffic management and control policies is a complex issue and requires detailed analysis of not only their impact on average speeds but also on other aspects of vehicle operation such as acceleration and deceleration.
423 citations
TL;DR: A model predictive control approach to optimally coordinate variable speed limits for freeway traffic with the aim of suppressing shock waves is presented and a safety constraint that prevents drivers from encountering speed limit drops larger than, e.g., 10 km/h is included.
Abstract: When freeway traffic is dense, shock waves may appear. These shock waves result in longer travel times and in sudden large variations in the speeds of the vehicles, which could lead to unsafe situations. Dynamic speed limits can be used to eliminate or at least to reduce the effects of shock waves. However, coordination of the variable speed limits is necessary in order to prevent the occurrence of new shock waves and/or a negative impact on the traffic flows in other locations. In this paper, we present a model predictive control approach to optimally coordinate variable speed limits for freeway traffic with the aim of suppressing shock waves. First, we optimize continuous valued speed limits, such that the total travel time is minimal. Next, we include a safety constraint that prevents drivers from encountering speed limit drops larger than, e.g., 10 km/h. Furthermore, to get a better correspondence between the computed and applied control signals, we also consider discrete speed limits. We illustrate our approach with a benchmark problem.
419 citations
TL;DR: In this paper, the impact of variable speed limits (VSLs) displayed on roadside variable message signs (VMSs) on aggregate traffic flow behavior is investigated in more detail with real traffic data from a European motorway.
Abstract: Variable speed limits (VSLs) displayed on roadside variable message signs (VMSs) have emerged as a widespread traffic control measure on motorways in many countries, leading to substantial traffic safety benefits; however, there is no clear evidence of improved traffic flow efficiency in operational VSL systems The available information on VSL impact on aggregate traffic flow behavior is summarized, and the issue is investigated in more detail with real traffic data from a European motorway It is found that VSLs decrease the slope of the flow-occupancy diagram at undercritical conditions, shift the critical occupancy to higher values, and enable higher flows at the same occupancy values in overcritical conditions Implications of the derived findings for more efficient VSL control strategies are discussed
361 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2026 | 1 |
| 2025 | 60 |
| 2024 | 111 |
| 2023 | 182 |
| 2022 | 296 |
| 2021 | 156 |