The effect of variable message and speed limit signs on mean speeds and speed deviations

Úlfarsson, Gudmundur F.; Shankar, Venkataraman N.; Vu, Patrick

doi:10.1504/ijvics.2005.007586

Cited by 22 publications

(8 citation statements)

References 10 publications

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“…Ulfarsson et al (2005) evaluated the impact of variable speed limits posted on I-90 in the vicinity of Snoqualmie Pass, Washington State using empirical data. The study concluded that the use of variable speed limits caused a statistically significant reduction in mean vehicle speeds but no Hellinga and Mandelzys 6 consistent impact on variation on speed was found.…”

Section: Driver Reaction To Speed Limitsmentioning

confidence: 99%

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

Hellinga

Mandelzys

2011

J. Transp. Eng.

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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.

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Section: Driver Reaction To Speed Limitsmentioning

confidence: 99%

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

Hellinga

Mandelzys

2011

J. Transp. Eng.

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“…As reported in the literature , a proper VSL control can help smooth speed transition and consequently reduce the number of vehicle stops and shockwave impact on the traffic conditions . Hence, this study has further explored the following objective function of minimizing the speed variance along the target freeway for a VSL control:

min true \sum_{k} true \sum_{i} {(u_{i} (k) - u_{a v e})}^{2}

where, u ave is the average speed of the target freeway stretch, and is given as follows:

u_{a v e} = \frac{\sum_{k} \sum_{i} u_{i} (k)}{((), T^{c} true/ normalΔ T) \cdot N}

…”

Section: Basic Proactive Control Modelmentioning

confidence: 89%

“…The VSL is initially designed to reduce the speed difference on some hazardous highway segments so as to decrease the rear‐end collisions and improve traffic safety . Recently, it has been recognized that VSL may also offer the potential to mitigate traffic congestion and improve traffic efficiency at work‐zones and freeway bottlenecks.…”

Section: Introductionmentioning

confidence: 99%

Exploratory analysis of an optimal variable speed control system for a recurrently congested freeway bottleneck

Yang

Chang

2014

J of Advced Transportation

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SUMMARYThis study presents two models for proactive variable speed limit (VSL) control on a recurrently congested freeway segment. The proposed model uses embedded traffic flow relations to predict the evolution of congestion patterns over the projected time horizon, and then computes the time-varying optimal speed limit to smooth traffic flows. To contend with the uncertainties associated with drivers' responses to VSL control, this study has also proposed an advanced model that further adopts Kalman Filter to enhance the traffic state estimation. Both models have been investigated with two control objectives-travel time minimization and speed variance minimization. Our extensive simulation analysis with a VISSIM simulator, calibrated with field data from our previous VSL field demonstration, has revealed the benefits of the proposed VSL control models. Also, the experimental results indicated that the proposed advanced models with both control objectives can significantly reduce the travel time over the recurrent bottleneck locations. With respect to several selected measure of effectiveness (MOEs), such as average number of stops and average travel time, the research results confirm that the control models with the objective of minimizing speed variance can offer the promising properties for field implementation.

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“…However, including only free-flow speeds does not allow the researcher to include traffic characteristics as explanatory variables when estimating operating speeds. Previous researchers have included traffic characteristics in the speed model specification, which provides insights to the range of speeds observed on a highway segment while still allowing evaluation of predicted free-flow speeds by setting traffic flow to a low value (27,28). This speed modeling practice also allows exploration of speed-highway geometry relationships at all points along the speed-flow curve.…”

Section: Free-flow Speedsmentioning

confidence: 99%

New Insights on Evaluations of Design Consistency for Two-Lane Highways

Himes

Donnell

Porter

2011

Transportation Research Record: Journal of the Transportation R

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Operating speed prediction models along horizontal curves of two-lane rural highways have been the topic of a significant body of literature. Operating speed models for two-lane rural highway tangents and for horizontal curves on low-speed urban streets also exist but are less developed. These models, estimated primarily by means of ordinary least squares regression, generally use aggregate-level data to estimate the effect of geometric design variables on the mean or 85th percentile operating speed but do not explicitly consider measures of speed dispersion (e.g., standard deviation). Most existing models consider speeds of free-flow passenger vehicles; traffic flow effects on speed are generally not quantified. Finally, published literature shows that researchers have not converged on a consistent modeling practice about the use of posted speed limit as an explanatory variable in operating speed models. Collectively, these issues may lead to design consistency assessments that are not truly reflective of the operating conditions along a two-lane highway. These issues are explored in this paper with the use of operating speed data collected at multiple points along eight two-lane highway segments. A simultaneous equations approach is used to estimate a three-equation model of the posted speed limit, mean speed, and speed deviation. The predicted 85th percentile speed is compared with the observed 85th percentile speed along a high-speed, two-lane rural highway. Predicted 85th percentile operating speeds along the same high-speed highway determined with the Interactive Highway Safety Design Model design consistency module are also compared with observed 85th percentile speeds as a basis for evaluating the simultaneous equations approach. Finally, the paper proposes an alternative approach to evaluating design consistency that uses inferred design speed.

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The effect of variable message and speed limit signs on mean speeds and speed deviations

Cited by 22 publications

References 10 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

Exploratory analysis of an optimal variable speed control system for a recurrently congested freeway bottleneck

New Insights on Evaluations of Design Consistency for Two-Lane Highways

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