Variable speed limits: safety and operational impacts of a candidate control strategy for an urban freeway

Allaby, P; Hellinga, Bruce; Bullock, Mara

doi:10.1109/itsc.2006.1706858

Cited by 16 publications

(21 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…avoid transitioning directly from 100 km/h to 60 km/h). For brevity, the specific transition zone logic is not described in this paper but is described in detail in the literature (Allaby, 2006;Allaby et al, 2007).…”

Section: Vsl Sensitivity To Speed Limit Compliance Simulation Frameworkmentioning

confidence: 99%

Impact of Driver Compliance on the Safety and Operational Impacts of Freeway Variable Speed Limit Systems

Hellinga

Mandelzys

2011

J. Transp. Eng.

View full text Add to dashboard Cite

Variable Speed Limit (VSL) systems enable freeway system managers to dynamically change the posted speed limit on a section of roadway in response to varying conditions. VSL system goals may include homogenizing traffic flow, improving safety, and/or reducing driver stress.Although it is understood that the effectiveness of VSL systems is impacted by the level of driver compliance, which itself is influenced by the extent of speed limit enforcement, very little is known about the strength of these impacts. This paper makes use of a simulation model to evaluate the sensitivity of the safety and operational impacts of VSL to driver compliance.Several scenarios for driver compliance were modeled using the PARAMICS microscopic traffic simulator. Findings indicated that VSL impacts are very sensitive to the level of driver compliance. Safety was shown to be positively correlated with the level of compliance and travel time was shown to be negatively correlated. However, it was also found the magnitude of the impact is strongly influenced by the VSL control strategy (i.e. set of rules for incrementing and decrementing the speed limits) being used. Therefore, selection of the VSL control strategy cannot be done independently of the decision regarding speed limit enforcement.

show abstract

Section: Vsl Sensitivity To Speed Limit Compliance Simulation Frameworkmentioning

confidence: 99%

Impact of Driver Compliance on the Safety and Operational Impacts of Freeway Variable Speed Limit Systems

Hellinga

Mandelzys

2011

J. Transp. Eng.

View full text Add to dashboard Cite

show abstract

“…A state of sudden deceleration may increase the likelihood of rear-end collisions and often occurs as a traffic queue is formed during recurrent or non-recurrent congestion. A detailed description of the method for calculating the spatial variation of speed, represented by precursor Q, is provided by Allaby [3].…”

Section: Methodsmentioning

confidence: 99%

“…For each of the crashes in the crash database two control factor conditions (time of day and geometric configuration) were also recorded. A detailed description of the calibration data is provided by Allaby [3].…”

Section: Datamentioning

confidence: 99%

See 1 more Smart Citation

Sensitivity of a real-time freeway crash prediction model to calibration optimality

Samimi

Hellinga

2012

Eur. Transp. Res. Rev.

View full text Add to dashboard Cite

Background Real-time crash prediction models are often structured as general log-linear categorical models which must be calibrated using an extensive database. However, there is no method to optimally select the number of categories and the values that define the boundaries between categories when representing continuous measures as categorical variables within the log-linear model. This raises the question of how important the calibration is to the safety impacts estimated when using the crash prediction model. In this paper, we examined the impact that the process used to calibrate the crash prediction model has on estimates of safety impacts of a variable speed limit system. Methods Two calibration methods were compared, namely a heuristic ad hoc method and a nearoptimal method. Both methods were applied to calibrate a crash prediction model using the same set of data from an urban freeway in Ontario, Canada. The calibrated crash prediction models are used to evaluate the safety benefits of a candidate variable speed limit system under three different traffic demand levels (Peak, Near-Peak, and Off-Peak). Concluding remarks It was found that safety improvements estimated by the two calibrated crash prediction models are within approximately 13% of each other for the Peak and Near-Peak scenarios, but differ by a larger amount for the Off-Peak scenario. However, despite these differences in the estimated magnitude of the safety impacts, the sign of the impact (i.e. increase versus decrease in safety) were consistent irrespective of the calibration method used. The results suggested that the safety impacts provided by the crash prediction model are robust in that they are relatively insensitive to the optimality of the calibration.

show abstract

“…The literature on the effectiveness of VSL systems on the simultaneous improvement of both mobility and safety has been of mixed results (Lee et al, 2006;Abdel-Aty et al, 2006Allaby et al, 2006). Findings differed from one location to another based on congestion level and network topology.…”

Section: Literature Reviewmentioning

confidence: 99%

Variable speed limit: A microscopic analysis in a connected vehicle environment

Khondaker

Kattan

2015

Transportation Research Part C: Emerging Technologies

238

103

View full text Add to dashboard Cite

a b s t r a c tThis paper presents a Variable Speed Limit (VSL) control algorithm for simultaneously maximizing the mobility, safety and environmental benefit in a Connected Vehicle environment. Development of Connected Vehicle (CV)/Autonomous Vehicle (AV) technology has the potential to provide essential data at the microscopic level to provide a better understanding of real-time driver behavior. This paper investigated a VSL control algorithm using a microscopic approach by focusing on individual driver's behavior (e.g., acceleration and deceleration) through the use of Model Predictive Control (MPC) approach. A multi-objective optimization function was formulated with the aim of finding a balanced trade-off among mobility, safety and sustainability. A microscopic traffic flow prediction model was used to calculate Total Travel Time (TTT); a surrogate safety measure Time To Collision (TTC) was used to measure instantaneous safety; and, a microscopic fuel consumption model (VT-Micro) was used to measure the environmental impact. Real-time driver's compliance to the posted speed limit was used to adjust the optimal speed limit values. A sensitivity analysis was conducted to compare the performance of the developed approach for different weights in the objective function and for two different percentages of CV. The results showed that with 100% penetration rate, the developed VSL approach outperformed the uncontrolled scenario consistently, resulting in up to 20% of total travel time reductions, 6-11% of safety improvements and 5-16% reduction in fuel consumptions. Our findings revealed that the scenario which optimized for safety alone, resulted in more optimum improvements as compared to the multi-criteria optimization. Thus, one can argue that in case of 100% penetration rates of CVs, optimizing for safety alone is enough to achieve simultaneous and optimum improvements in all measures. However, mixed results were obtained in case of lower % penetration rate which showed higher collision risk when optimizing for only mobility or fuel consumption. This indicates that with such % penetration rate, multi-criteria optimization is crucial to realize optimum and balanced benefits for the examined measures.

show abstract

Variable speed limits: safety and operational impacts of a candidate control strategy for an urban freeway

Cited by 16 publications

References 5 publications

Impact of Driver Compliance on the Safety and Operational Impacts of Freeway Variable Speed Limit Systems

Impact of Driver Compliance on the Safety and Operational Impacts of Freeway Variable Speed Limit Systems

Sensitivity of a real-time freeway crash prediction model to calibration optimality

Variable speed limit: A microscopic analysis in a connected vehicle environment

Contact Info

Product

Resources

About