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Ng Narrows In On Solution To Reduce Traffic Congestion

Published: June 17, 2013

Sometimes less is more. At least that’s the thinking of Chen Ng when it comes to addressing the problem of overcrowded highways.

Ng, an assistant professor of economics at CSULB for five years, and whose work focuses on urban and transportation economics, co-authored a paper with her advisor, Kenneth Small, while finishing up her Ph.D. at UC Irvine. The project was funded by the University of California Transportation Center and Ng continued working on the paper during her first two years at CSULB. They concluded that narrower—and in turn additional lanes—might be a solution.

Her interest in transportation economics and desire to attack the problem of traffic congestion gained impetus from her own experiences of sitting in and maneuvering through it on a daily basis.

“When I drive and look at all the other cars sitting in traffic,” she said, “it gives me the incentive to work on solving the problem of congestion.

“Traffic congestion is a big problem in a lot of urban areas and you don’t face congestion just on the weekdays. You often get it on the weekends, too,” she continued, remarking that only off-peak drivers are able to generally travel at high speeds to take full advantage of what their paper labeled as “extraordinary engineering investments” called highways. “Economists have talked about a lot of ways to alleviate traffic congestion. One of those is what is called ‘congestion pricing’—essentially having tolls on congested roads, especially during peak hours, to reduce the number of drivers. This is similar to what we see on the 91 expressway, where the tolls are raised and lowered depending on the amount of traffic in the express lanes in order to maintain a target speed.”

As one can imagine, however, “congestion pricing” has been a very hard sell overall. For example, New York City Mayor Michael Bloomberg’s plan to implement a toll in Manhattan—similar to the one enacted in London—was rejected by state lawmakers in 2007.

“We are trying to think of other ways to alleviate congestion,” said Ng, who earned her bachelor’s degree at Princeton. “One thing that often comes up is, ‘Why don’t we just build more roads?’ One problem with building more roads, especially expressways in urban areas, is that both construction and land acquisition costs are very high.”

Ng and Small, a research professor and professor emeritus in the Department of Economics at UCI, began to think outside of the box.

“Congestion arises because it’s a capacity problem,” Ng said. “The number of cars that can use the road is limited and so the idea is that, if we have narrower lanes, we can put in more lanes to increase capacity.”

Say what? Narrower lanes on freeways already full of distracted and speeding drivers? Ng is aware their proposal won’t be an easy sell either, but she’s convinced it could work.

“We might get some resistance from insurance companies, or from truck drivers because they need wide lanes,” said Ng, noting that it is uncertain whether the compact road design—especially when accompanied by lower speed limits—will reduce or increase safety. “One possibility is limiting trucks to driving only in the right-handmost lane since they would have more room to maneuver as they would have the additional width of the shoulder, or perhaps make the road autos only.

“Because of congestion drivers are already going so slow that if we add more lanes, that will relieve some of that congestion,” she added. “You still wouldn’t be able to go 65 miles per hour during the morning rush hour, but at least you might be able to go 50 miles per hour, so at least you’d be moving. Also, reducing congestion is good in the sense that we have a lot of air pollution as a result of all those idling cars, it’s a waste of people’s time and people get stressed out, too. However, we do recognize that there are tradeoffs involved.”

More specifically, Ng and Small suggest, for example, having a three-lane road with 10-foot wide lanes instead of a two-lane road with 12-foot lanes.

Chen Ng
PHOTO BY DAVID J. NELSON
Chen Ng

“With some arrangement of the shoulder widths you could fit a three-lane road—which allows for a higher capacity, more cars—in the same area as the two-lane road,” said Ng. “The tradeoff is that the narrower lanes would result in a decrease in free-flow speed; that is, off-peak drivers won’t get to go as fast. In addition, accident rates might tend to be a little higher on roads with narrower lanes, but there is mixed evidence on that issue.” These things are all tradeoffs that have to be taken into account, according to Ng, adding that it’s important to have a careful cost-benefit analysis of all these issues before implementing this idea.

“The standard in the U.S. is that interstates have to have 12-foot lanes,” said Ng, who noted that such standards also specify lane and shoulder widths, sight distance, grade and other characteristics that require a lot of land and extensive infrastructure such as ramps and bridges.

However, there have been examples of narrowing lanes. It was done locally when back in 1995 a stretch of the 405 freeway near LAX was restriped into 11-foot lanes and shoulders were converted to create additional lanes.

Studying U.S. models, Ng and Small looked at older routes like the Arroyo Seco Parkway, formerly known as the Pasadena Freeway, where past downtown it’s no longer an interstate expressway, but rather a winding road; the Baltimore-Washington Parkway; and an extensive parkway system on Long Island in New York. Each features architecturally interesting structures, attractive landscaping and designs that fit into the surrounding landscape. They also provide ample capacity and are much cheaper than modern interstates.

“That’s how routes used to be,” she said. “They would fit more into the landscape; they didn’t raze down the mountains to build nice, straight freeways. We’re not just talking about narrower lanes here; our idea is to have what we call a lower environmental footprint, so we would have roads that conform more to the geography. They might not meet our strict interstate standards, but they would be more environmentally friendly.”

The authors are working on an upcoming follow-up paper continuing to address this issue, where they are extending the traditional economic model of road investment to incorporate the aforementioned tradeoffs between speed and capacity.

“We wrote this paper to encourage people to think of this as a possible alternative, especially since building freeways is very expensive,” she said. “It’s not going to be the best scenario in every situation, especially if traffic volumes are low in a city and congestion is not much of a problem. In that case, a freeway that offers a higher free-flow speed may be preferred. But in a city where congestion happens throughout the day, you might place a higher weight on the capacity allowed by more lanes than on the high speeds enjoyed by relatively few people during off-peak hours.”