News Tagged: Reliability

2 Entries Tagged

OTREC research aids Oregon Department of Transportation with placing traffic devices

Posted on October 16, 2013

OTREC research recently helped the Oregon Department of Transportation (ODOT) determine where to place traffic management devices.
 
Driving down the freeway, motorists usually appreciate seeing lit-up signs with changing numbers that tell the estimated drive time to an upcoming location. These variable message signs (VMS), also called changeable (CMS) or dynamic message signs (DMS), provide drivers with information that helps them make route decisions.
 
The Federal Highway Administration (FHWA) has put a high priority on the use of VMS to provide travel time estimates to the public.
 
Drive times on the VMS are estimated based on sensors which measure the speed of traffic, and an algorithm to calculate how the traffic will flow.
 
Given the many variables involved, it can be challenging to estimate reliable drive times. ODOT is particularly challenged: the Portland area, with its tight, circular freeway system, can become severely congested after only a couple of minor incidents.
 
That means Dennis Mitchell, ODOT’s Region 1 Traffic Engineer, has an interesting job.

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Tags: congestion, devices, management, odot, otrec, psu, reliability, traffic, travel time, vms

Innovative look at effects of bottlenecks wins Transportation Research Forum award

Posted on April 7, 2011

OTREC researchers at Portland State University won the best paper award at the annual Transportation Research Forum for examining the effects of freeway traffic bottlenecks on costs. Graduate student Alex Bigazzi and Miguel Figliozzi, an associate professor of Civil and Environmental Engineering, submitted the paper for the forum, held in March in Long Beach, Calif.

Traffic flows can break down more or less at random as the freeway approaches its capacity. Although drivers pay a high price for bottlenecks both in their time and fuel costs, earlier models have taken an oversimplified look at how the uncertainty associated with how bottlenecks form, and how long they last, affect time and fuel costs. Without incorporating uncertainty, previous models underestimate the impact of congestion and bottlenecks.  The paper, called “A Model and Case Study of the Impacts of Stochastic Capacity on Freeway Traffic Flow Benefits and Costs,” takes into account the range and frequency with which these random or uncertain traffic breakdowns occur.  

Research detailed in the paper stemmed from an OTREC project, Value of Reliability. Figliozzi had considered the concept of reliability for years, even using it in his modeling class as an example on how to analyze the impact of uncertainty and combine diverse datasets and models—traffic, congestion, and emissions—into a cohesive model.

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Tags: alex bigazzi, bottlenecks, freeway capacity, miguel figliozzi, reliability

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