The Science Of Traffic

How do engineers explain mysteries such as phantom traffic jams and why a brief drop in volume can trigger a traffic jam?

1 minute read

July 1, 2005, 9:00 AM PDT

By Chris Steins @planetizen


" 'Weaving is the worst condition for traffic flow,' says Prof. Polus. Because drivers in heavy traffic brake when a car pulls into their lane, and because it takes time to get back up to speed, there are larger and constantly-changing gaps between vehicles. That invites yet more cars to change lanes, propagating a wave of stop-and-go traffic that cuts the number of cars in a stretch of road by about 10%, calculates Prof. Polus, who will present his work at the 16th International Symposium on Transportation and Traffic Theory at the University of Maryland this month. That may not sound so dire, but in rush hour the result is a five-mile backup, his calculations show. In congestion, be content with the lane you're in."

[Editor's note: The link below is available for a period of 7 days.]

Thanks to Chris Steins

Friday, July 1, 2005 in Wall St. Journal

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Cover CM Credits, Earn Certificates, Push Your Career Forward

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

June 18, 2025 - Diana Ionescu

Rendering of Shirley Chisholm Village four-story housing development with person biking in front.

San Francisco's School District Spent $105M To Build Affordable Housing for Teachers — And That's Just the Beginning

SFUSD joins a growing list of school districts using their land holdings to address housing affordability challenges faced by their own employees.

June 8, 2025 - Fast Company

Woman and young girl looking at subway map, woman pointing.

Can We Please Give Communities the Design They Deserve?

Often an afterthought, graphic design impacts everything from how we navigate a city to how we feel about it. One designer argues: the people deserve better.

June 9, 2025 - John Pobojewski

Map of EV charging ports in rural U.S. communities.

The EV “Charging Divide” Plaguing Rural America

With “the deck stacked” against rural areas, will the great electric American road trip ever be a reality?

5 hours ago - The Daily Yonder

Google street view of Bedford Avenue in Brooklyn with pedestrians crossing a crosswalk and cyclist in the bike lane.

Judge Halts Brooklyn Bike Lane Removal

Lawyers must prove the city was not acting “arbitrarily, capriciously, and illegally” in ordering the hasty removal.

6 hours ago - StreetsBlog NYC

Close-up of cracked and damaged two-lane roadway with double yellow stripes on a bright sunny day.

Engineers Gave America's Roads an Almost Failing Grade — Why Aren't We Fixing Them?

With over a trillion dollars spent on roads that are still falling apart, advocates propose a new “fix it first” framework.

June 19 - Transportation for America