Yogi Berra could have been talking about the New Jersey Turnpike when he said, "Nobody goes there anymore; it's too crowded."

The road is famously congested between Exits 6 and 9, near Trenton, where 12 lanes dwindle to six. Construction to widen that chokepoint is scheduled to start early next year, now that higher tolls have been approved to pay for the $2.5 billion project.

But will a wider turnpike bring long-awaited relief to commuters and truckers? Or will it just bring more commuters and truckers?

Highway engineers have long dealt with the phenomenon of "induced demand," the tendency for new lanes to attract new drivers. Human nature and traffic science make it inevitable, transportation experts say.

The goal of the wider turnpike is to accommodate traffic needs through 2032. By then, state highway officials predict, northbound traffic on the turnpike will be 67 percent higher than in 2005, and southbound traffic is forecast to increase by 92 percent.

But the new lanes - scheduled for completion by early 2013 - may bring more drivers much sooner, traffic and planning experts say.

"When you make those kinds of improvements, capacity gets eaten up very quickly. About 80 percent of the new capacity gets used up right away," said Donald Shanis, deputy executive director of the Delaware Valley Regional Planning Commission. "Any time you make a trip easier, you encourage more auto trips."

Robert Noland, professor and director of the Voorhees Transportation Center at Rutgers University, said his research had shown that "if you add more capacity, it's likely you'll increase the number of cars."

That's fine if the goal is to increase the number of travelers, he said, but it's not fine if the goal is to reduce congestion. It might just push the bottleneck elsewhere, he noted.

A more effective way to reduce congestion, Noland said, is to increase tolls at peak travel times. He cited London, where drivers pay a congestion charge of about $13 to enter the central city between 7 a.m and 6 p.m.

But Noland, who until this year was a professor of transport and environmental policy at Imperial College London, noted that about 85 percent of London commuters used public transit, making the charge "politically easy to do."

In New Jersey, most trips are by car, so congestion pricing likely would meet with much more opposition. In addition, mass transit is less available than in London.

Major road-widening projects are also in the works for 17 miles of the Garden State Parkway (between mileposts 63 and 80) and 23 miles of the Atlantic City Expressway (from the Garden State Parkway to the Route 73 interchange). Tolls are being raised on those roads to pay for the projects.

Around the nation, Shanis said, "we're pretty close to the limits" of road-building. More money and attention need to be spent on mass transit and the development of housing and jobs near transit hubs, he said.

Indeed, $1.25 billion from the toll increases on the turnpike and parkway is earmarked to help pay for a new rail tunnel under the Hudson River into New York City, allowing more commuters to travel by train.

Shanis said there was a good argument for widening the turnpike's bottleneck: the heavy freight traffic between New York and Philadelphia and beyond and the lack of alternatives for many drivers.

"It's pretty hard to squeeze that out of Amtrak or the airlines," he said.

An advocate for motorists, the AAA Clubs of New Jersey, contends the turnpike "is a good example of where induced demand is not a viable argument against the widening," spokesman David Weinstein said.

"Capacity had been reached there about 10 years ago. . . . This is something that should have been done a decade ago," he said.

Even without more lanes, more drivers can be expected. Motorists learned that with the Schuylkill Expressway, where traffic has increased more than 50 percent since the mid-1980s, when the highway was rebuilt without additional lanes.

Traffic experts say drivers tend to take the routes best for them regardless of the broader impact.

That "selfish commuting" means drivers continue "to get on the same roads and wish that not so many others had also chosen to do so," Tom Vanderbilt writes in

Traffic: Why We Drive the Way We Do

, a new book on driving behavior - inspired by being stuck in traffic on the New Jersey Turnpike.

Toll Road Expansion

The widening of New Jersey's toll roads will start early next year. Here is the tentative schedule.

New Jersey Turnpike:

The first eight of 28 construction contracts will be awarded for work scattered over the 35-mile project, with construction scheduled to start by March.

Most of the work will be outside the existing lanes, so the impact on traffic is expected to be limited, and construction will not be restricted to off-peak hours.

The New Jersey Turnpike Authority has not acquired all the land it needs, so the widening will begin where land acquisition is not an issue.

The $2.5 billion project is scheduled to be completed by early 2013.

Garden State Parkway:

Separate contracts will be awarded for three segments of the project. Work on the first segment, between mileposts 75 and 80, is scheduled to start May 19. Work on the other two segments, between mileposts 63 and 70 and mileposts 70 and 75, is to start June 27.

Two lanes will be maintained in each direction during construction. Only when the Birch Street Bridges are demolished will construction will be restricted to off-peak hours and the parkway closed.

The $200 million project is expected to take about 15 months.

Atlantic City Expressway:

The $130 million widening of 23 westbound miles may start as early as the end of 2009.

The first phase will be the nine miles from the Garden State Parkway intersection to milepost 17. The second will be from milepost 17 to the Farley Plaza, and the third will be from the Farley Plaza to Exit 31.

No completion date has been set.

- Paul Nussbaum