Evaluating the Effects of a Congestion and Weather Responsive Advisory Variable Speed Limit System in Portland, Oregon

Downey, Matthew

doi:10.15760/etd.2394

Cited by 1 publication

(2 citation statements)

References 8 publications

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“…They aim to enhance safety through reducing the likelihood of rear-end crashes and enhance capacity by harmonizing the flow of traffic. This can also result in improved travel time reliability (Downey, 2015). VSL systems generally consist of detector stations, weather detectors, CCTV surveillance, VSL signs, a control center and a communications system.…”

Section: Variable Speed Limitsmentioning

confidence: 99%

“…However, the analysis did not show any significant safety benefits with crash increases, based on a small sample of data from a 5 month period after VSL activation (Downey, et al 2015). A more recent study summary of safety on the corridor was conducted by ODOT using multiple data sources in a simple comparison of crash numbers before and after the VSL implementation showing a 13% decline with 911 call data and 20% decline with official crash data (ODOT, 2016).…”

Section: Or 217 Evaluationsmentioning

confidence: 99%

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Benefits of Advanced Traffic Management Solutions: Before and After Crash Analysis for Deployment of a Variable Advisory Speed Limit System

Chambers

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Variable speed limit (VSL) systems are important active traffic management tools that are being deployed across the U.S. and indeed around the world for relieving congestion and improving safety. Oregon's first variable advisory speed limit signs were activated along Oregon Highway 217 in the summer of 2014. The variable advisory speed system is responsive to both congestion and weather conditions. This seven-mile corridor stretches around Western Portland and has suffered from high crash rates and peak period congestion in the past. VSL systems are often deployed to address safety, mobility and sustainability related performance. This research seeks to determine whether the newly implemented variable advisory speed limit system has had measurable impacts on traffic safety and what the scale of the impact has been. The research utilizes a beforeafter crash analysis with three years of data prior to implementation and around 16 months after. Statistical analysis using an Empirical Bayes (EB) approach will aim to separate the direct impacts of the variable advisory speed limit signs from the long term trends on the highway. In addition, the analysis corrects for the changes in traffic volumes over the study period. Three data sources will be utilized including Washington County 911 call data, Oregon incident reports, and official Oregon Department of Transportation crash data reports. The analysis v results are compared between data sources to determine the reliability of 911 call data as a proxy for crash statistics. The conclusions should be able to provide an indication of whether variable advisory speed limits can provide increased safety along high crash corridors.

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Section: Variable Speed Limitsmentioning

confidence: 99%

Section: Or 217 Evaluationsmentioning

confidence: 99%

Benefits of Advanced Traffic Management Solutions: Before and After Crash Analysis for Deployment of a Variable Advisory Speed Limit System

Chambers

View full text Add to dashboard Cite

show abstract

Evaluating the Effects of a Congestion and Weather Responsive Advisory Variable Speed Limit System in Portland, Oregon

Cited by 1 publication

References 8 publications

Benefits of Advanced Traffic Management Solutions: Before and After Crash Analysis for Deployment of a Variable Advisory Speed Limit System

Benefits of Advanced Traffic Management Solutions: Before and After Crash Analysis for Deployment of a Variable Advisory Speed Limit System

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