congestion | Transportation Research and Education Center

A view through the front windshield of a car, with two bicyclists on the road ahead.

Do Bicycles Slow Down Cars on Low Speed, Low Traffic Roads? Latest Research Says “No”

Jul 21, 2020

Photo by Pav_1007 on iStock

Evidence from Urban Roads without Bicycle Lanes on the Impact of Bicycle Traffic on Passenger Car Travel Speeds

Jaclyn Schaefer, Miguel Figliozzi, and Avinash Unnikrishnan; Portland State University

The new article Evidence from Urban Roads without Bicycle Lanes on the Impact of Bicycle Traffic on Passenger Car Travel Speeds published in Transportation Research Record, the Journal of the Transportation Research Board, demonstrates that bicycles do not significantly reduce passenger car travel speeds on low speed, low volume urban roads without bicycle lanes. Authored by Jaclyn Schaefer, Miguel Figliozzi, and Avinash Unnikrishnan of Portland State University, the research shows that differences in vehicle speeds with and without cyclists were generally on the order of 1 mph or less – negligible from a practical perspective.

A concern raised by...

Exiting the Freeway: Travel Time Reliability on Urban Arterials

Aug 14, 2019

Photo by CreativeNature_nl

Understanding Factors Affecting Arterial Reliability Performance Metrics

Avinash Unnikrishnan, Sirisha Kothuri, and Jason Anderson; Portland State University

Exploring New Solutions to Urban Congestion Through a Network of Traffic Signal Controls

Apr 04, 2019

Photo by Canetti

Principal Investigator: Gerardo Lafferriere, Portland State University

Project Overview: A Decentralized Network Consensus Control Approach for Urban Traffic Signal Optimization

Learn more about this research by viewing the Executive Summary and the full Final Report on the Project Overview page.

Automobile traffic congestion in urban areas comes with significant economic and social costs for everyone. According to the 2015 Urban Mobility Report, the total additional cost of congestion was $160 billion. As more people move to metropolitan areas, the problems only intensify. The latest NITC report offers a new approach to urban traffic signal control based on network consensus control theory which is computationally efficient, responsive to local congestion, and at the same time has the potential for congestion management at the network level.

Traffic signals represent a significant bottleneck. As...

GPS data can identify congestion hot spots

Jan 07, 2016

Traffic congestion on urban roadways can influence operating costs and cause travel delays.

Portland State University master’s students Nicholas Stoll and Travis Glick will present a paper introducing solutions for locating the sources of congestion at the 2016 annual meeting of the Transportation Research Board.

With their faculty advisor, Miguel Figliozzi, Stoll and Glick looked into using bus GPS data to identify congestion hot spots.

By using high-resolution GPS data to visualize trends in bus behavior and movement, the researchers were able to examine the sources of delay on urban arterials.

These visualizations, which can be in the form of heat maps or speed plots like the one shown here on the right (an application of numerical method applied to a 2,000 ft segment of SE Powell), can be used by transportation agencies to identify locations where improvements are needed. For example, adding a queue jump lane at a congested intersection can improve flow.

The researchers used fine-grained bus data provided by TriMet to create the visualizations. Buses have been used as probes to estimate travel times before, but with...

Light rail reduces auto traffic, cuts emissions, study finds

Jul 03, 2014

For the first time, researchers have shown that installing light rail on an existing travel corridor not only gets people out of their cars, but reduces congestion and air pollution.

In the study, planners at the University of Utah measured impacts of a new light rail line in Salt Lake City (University Line) on an existing major thoroughfare (400/500 South). Their analysis showed that traffic near the University has fallen to levels not seen since the 1980s, even as the number of students, faculty and staff at the university has increased, and the commercial district along the corridor has expanded.

"This is the first study to document important effects of light rail transit on traffic volumes,” said Reid Ewing, professor of city and metropolitan planning at the University of Utah and lead author on the study. “Since the University TRAX line opened, there has been increased development in the 400/500 South travel corridor, yet traffic on the street has actually declined. Our calculations show that without the University TRAX line, there would be at least 7,300 more cars per day on 400/500 South, and possibly as many as 21,700 additional cars. The line avoids gridlock, as well as saves an additional 13 tons of toxic air pollutants. This is important knowledge for shaping future transportation policies.”

Andrew Gruber, executive director of the...

OTREC research aids Oregon Department of Transportation with placing traffic devices

Oct 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.

Traffic engineers work to ensure the safety and efficiency of public roadways and transportation systems. Mitchell constantly looks for ways to...

OTREC research looks into effects of traffic signal optimization

Aug 30, 2013

An OTREC project recently took an in-depth look at the travel-time and health-related effects of a new implementation of a state of the art adaptive traffic system.

Southeast Powell Boulevard is a multimodal urban corridor connecting highway US-26 through Portland, Oregon. The corridor is highly congested during morning and evening peak traffic hours. In October 2011, an adaptive traffic system called SCATS was deployed.

The primary function of SCATS, or Sydney Coordinated Adaptive Traffic System, is to mitigate traffic congestion. Using sensors (usually inductive loops) at each traffic signal, the system tries to find the best cycle time and phasing along the corridor as traffic demand patterns change.

In this integrated multimodal study, OTREC researchers looked at the corridor’s traffic speed and transit reliability, before and after the implementation of SCATS. In addition, a novel contribution of this study was to study the link between signal timing and air quality.

To determine the impact of SCATS on traffic and transit performance, researchers established and measured performance measures before and after SCATS. The researchers used data provided by TriMet, Portland's transit authority, to compare transit times before and after SCATS as well as traffic volume data from two Wavetronix units that were installed by the City of Portland; these units collect traffic counts, speeds and classifications. For the air quality study, TriMet also...

Research explores the value of travel-time reliability

Apr 05, 2013

When planning their daily commute, most drivers account for the traffic they know is unavoidable: at peak times of day, like morning and afternoon rush hour, they probably allow extra time to get where they’re going.

The delays that are harder to accept are the unexpected ones, when accidents, road work, or a traffic bottleneck turn a thirty minute trip into an hour.

This unpredictable postponement leads to natural frustration on the part of drivers, as it may cause them to be late to work or late picking up children from school. A reliable road network is one in which this is a rare occurrence.

A project led by Portland State University’s Miguel Figliozzi explored the value of this travel-time reliability using a study of commuters’ route choice behavior, taking a look at the trade-offs between reliability, traffic congestion, and air pollution.

The details for the combined project can be found here.

In the first phase of the research, co-investigators David Levinson and Kathleen Harder of the University of Minnesota sought to measure the route choices drivers made in a real-world setting. Instead of just having people fill out a survey about whether they would choose to take major roads or the freeway to work, this study ambitiously...

Graduate student takes research to southeast Asia

Apr 05, 2013

Graduate student researcher Alex Bigazzi, of Portland State University, will present his work in Vietnam next week.

The Asia-Pacific Economic Cooperation (APEC) is hosting a transportation workshop in Ho Chi Minh city. The opportunity for Bigazzi to attend is the result of a spontaneous connection he made recently at a conference in Annapolis, Maryland, where he was giving a paper on truck-specific traffic management.

Large trucks contribute a large share of emissions, especially when traveling at a slow crawl through heavy traffic. Bigazzi’s work explores ways to mitigate the effects of this traffic congestion on air quality.

Bigazzi presented two papers at the 54th Annual Transportation Research Forum, which took place March 21-23 in Annapolis. One of them, “The Emissions Benefits of Truck-Only Lane Management,” offers a better understanding of the impacts of congestion on heavy-duty vehicles.

After a question-and-answer exchange, he was invited to present the same research in Vietnam’s largest city.

APEC’s 37^thTransportation Working Group Meeting will take place April 8^th through the 12^th, 2013, at a Sheridan...

OTREC Research Assistant To Improve Transportation At National Park

Jun 15, 2011

While the national parks system may have some of the most natural areas in America, there’s nothing natural about how most Americans travel through them: by car.

Todd Johnson, an OTREC graduate research assistant, is hoping to change that for at least one state park. The Eno Transportation Foundation recently chose Johnson for a year-long assignment to find ways to reduce traffic congestion at Arches National Park near Moab, UT. Every year, Eno puts out five assignments throughout the country to improve transportation at national parks and monuments.

Johnson, a Master of Science student in civil and environmental engineering at Portland State University, previously worked as a transportation interpreter at Rock Mountain National Park, encouraging people to take a shuttle service rather than driving. He has a similar goal for his stint at Arches.

“We want to get people out of their cars,” Johnson said. “Right now when the parking lots fill up, people park on the side of the road, creating a safety hazard and diminishing the beauty of the park. I will help with implementing solutions to deal with congestion using (Intelligent Transportation Systems) and social media.”

Johnson, an avid cyclist, will also be looking at encouraging alternative forms of transportation through Arches. The park is looking to construct more hiking and biking trails to prevent visitors from driving from one attraction to another, Johnson said. Currently, the park’s roads...

Pages