Frustrating, expensive traffic jams on the nation’s urban freeways are getting worse every day.
The 2002 Urban Mobility Study by the Texas Transportation Institute (TTI), released on June 20, revealed that travelers lost an average of 62 hours because of traffic congestion during 2000, compared with 16 hours per year in 1982. During the same period, the number of congested roadways grew from 34 percent to 58 percent, and daily congestion time jumped from 4.5 hours to seven hours.
TTI, the nation’s largest university-affiliated transportation research agency, is a member of the Texas A&M University System in College Station, TX. Its annual report, issued for the past 19 years, includes information from 75 urban areas and is the nation’s longest-running study of traffic problems.
The report showed the total costs of congestion in those urban areas in 2000 were $67.5 billion, the value lost from 3.6-billion hours of delay and 5.7-billion gallons of excess fuel consumed.
It also recognized that alleviating the growth of congestion is no small problem, giving as examples:
“To keep congestion from growing between 1999 and 2000 would have required 1,780 new lane-miles of freeway and 2,590 new lane-miles of streets, or an average of 6.2-million additional new trips per day taken by either carpool or transit … or operational improvements that allowed 3-percent more travel on the existing systems, or some combination of these actions. These events did not happen, and congestion increased.”
What Can Be Done?
Is there any hope for U.S. motorists and bus riders? Is a congestion-free traffic system possible?
Traffic researchers say that increasing the reliability of highway systems can at least slow the monster traffic growth.
Tim Lomax, co-author of the TTI report, told Construction Equipment Guide (CEG) that “relatively high-speed travel in the middle of a peak period in a densely populated urban area probably won’t happen as far as the general traffic stream is concerned.”
He added, however, that making freeway systems more reliable, informative, technologically advanced and predictable can reduce the growth in congestion.
“One way of reducing jams is pricing special lanes,” he said. “At present, all trips are assumed to have the same value. But suppose you had lanes where people could pay money to avoid congestion, showing they valued some trips more highly — like an important business meeting, attending an event for one of your children, or making a plane connection?”
An extension of the toll highway concept would treat transportation services like most other services in society. There would be a direct charge for using more important system elements.
“Depending on what society decides it values and wants to reward, we can create enough space for that to happen in some corridors, as well as car pool and High Occupancy Vehicle (HOV) lanes,” Lomax added. “Such lanes would be an option, which wouldn’t be possible for every highway. I don’t think we could build enough lanes to make them possible everywhere because they are expensive, impact the environment, and require public approval.”
Another promising approach, Lomax said, is “better coordination between traffic signals and transit systems.
“If a bus is behind schedule, or if it is full of people rather than empty, you would give it a higher priority,” he said. “A bus carrying 40 people is equivalent to 40 cars and could be given a green light at intersections.
“Right now, 40 cars can be detected by loops or pulses in the pavement but we can’t know that 40 people are on a bus or immediately tell whether it’s ahead of schedule or behind. We need a system, similar to that for airlines, which allows buses to talk with signal systems and relate where they are and where they’re supposed to be.”
When highways become more reliable, the report stated, motorists can make more informed decisions, adjusting their trip-travel habits.
“If people know when it will take twice as long to get to work, they may decide to telecommute from their homes or use public transit,” Lomax said.
The report pointed out that the Internet has facilitated electronic trips and that “using a computer or phone to work at home for a day, or just one or two hours, can reduce the peak system demand levels without dramatically altering lifestyles.”
Ramp Metering
Traffic signals that regulate traffic flow entering a freeway are considered one of the primary methods of preventing jams. At cross streets, for instance, 20 cars might be spaced out to enter at the best intervals.
Why couldn’t such computer-based techniques keep all traffic moving all the time?
“In theory, it seems plausible; however, in reality, we like our flexibility,” David Schrank, the other co-author of the report, told CEG.
“We don’t want a computer telling us when we can or can’t use whatever part we want to use. That’s not to say motorists wouldn’t be willing to wait a minute on a ramp, but if it tells them to wait a half-hour, they don’t like that kind of enforcement. They want to make their own decisions.”
Lomax agreed, “In a democratic society, there’s too much demand to keep freeways at 55 or 60 mi. per hour for a really long time. However, traffic signals can delay the onset of congestion.”
The study also highlighted “incident management” — closely monitoring freeways and quickly finding and removing stalled or crashed vehicles. It urged that this approach, and ramp metering, be “aggressively managed” in order to “significantly improve the predictability of transportation service.”
“While ramp signals, carpool lanes and other operational strategies may produce a modest decease in congestion,” the report said, “they can more significantly reduce variations in how roadways operate, and reduce traveler frustration in the process.”
Commenting on the report, Pete Ruane, president and chief executive officer of the American Road & Transportation Builders Association (ARTBA) in Washington, D.C., suggested additional innovative approaches.
“Congress should also support new ways to add highway capacity,” he said. “Toll-financed truck-only lanes should be considered for existing interstate highway right of way, where appropriate. Double decking and tunneling in some urban areas — while expensive — should also be seriously considered as options.”
Integrated Systems
The researchers told CEG that “integrated” techniques of speeding traffic, combining many approaches, are being deployed in corridors where they are acceptable to the public.
While realistically discounting the possibility of keeping cars moving at 55 mph through rush hours in urban areas, Lomax and Schrank don’t entirely shut the door on reaching such a goal.
“With Intelligent Transportation System (ITS) funding over the past few years, we have reached the point of a backbone communications system,” said Lomax. “A number of intelligent systems are deployed. Others are tested and are about to be deployed. We will see a lot more integrated systems over the next five or 10 years. These may reduce congestion, but a slower growth in congestion is more likely.”
“We are moving towards an all-encompassing integrated system, but it will take a while,” said Schrank. “In the past, we have seen small case study examples on one freeway. Now we are starting to see systems covering wider areas, also more integrated systems.
“I don’t know how long it [uninterrupted traffic flow] would take to achieve throughout the country,” Schrank added. “Yes, it’s conceptually possible, but millions of people moving within an hour of each other will put stress on whatever transportation system you have. However, it was hard to envision the era of cell phones 10 years ago. Who knows what will happen in the next 10 or 20 years?”
Schrank thought a more realistic scenario, however, is that “there will always be some congestion in urban areas; most of the transportation community recognizes that; they are working towards solutions that shorten the duration or intensity of congestion as opposed to eliminating it.”
Road Expansions
The report said that “adding capacity [to highways and transit systems] remains the best-known and probably most frequently used, improvement option,” and is essential for handling increasing demand in growing areas.
“Even the best efficiency-boosting ideas can’t entirely take the place of new roads,” it said.
In areas where the rate of roadway additions was approximately equal to travel growth, the report added, congestion (travel time) increased much more slowly (only one-fourth to one-third as much) than in other places where new roads lagged behind new volume.
“The matter is partly an individual state department of transportation issue,” said Lomax. “Do they want to spend more on traffic? There’s certainly a case to be made for that. Adding more road space is part of the solution and a viable option in some corridors. In others, there’s no support, in part because of environmental/social impact, and partly because of funding issues.”
But the report said that road expansion, though important, isn’t a “wonder drug” to cure traffic jams.
“In many of the nation’s most congested corridors there does not seem to be the space, money, and public approval to add enough roadway to create an acceptable condition,” the report stated. “Only about half of the new roads needed to address congestion with an ’all roads’ approach were added between 1982 and 2000.”
And, ironically, the effort to improve mobility may itself cause congestion.
The report pointed out that “better techniques in managing construction and maintenance programs can make a difference.”
Also part of the solution, the report said, is planning land-use development patterns in urban areas to reduce the use of private vehicles.
“A vision of the future is important,” it stated. “A consensus about how the urban area should arrange the jobs, schools, homes, shops, parks, and other land uses is difficult to achieve, but is an important exercise … The fact is, transportation system demand and land use patterns are linked and influence each other.”
The Urban Mobility Study is funded by a consortium of 10 state transportation agency sponsors. The 75 urban areas that supplied data range from New York City to Boulder, CO.
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