Stuck in gridlock: Why 405 expansion didn't reduce rush hour delay

I-405 near Mullholand Drive exit in the congested Sepulveda Pass between the San Fernando Valley and West Los Angeles.
I-405 near Mullholand Drive exit in the congested Sepulveda Pass between the San Fernando Valley and West Los Angeles. macappsaddict/Flickr

A recent study commissioned by Metro crowed that drivers on the Sepulveda Pass section of the 405 freeway, one of the most congested stretches in the nation, are benefiting from a shorter rush hour after a five-year expansion project.

But the $1.1 billion project didn't reduce commute times during rush hour - they have increased by about a minute, according to a  previous study.

"The net gain for my commute was zero,"said Chris Simmons, a visual effects artist who travels from the San Fernando Valley through the Sepulveda Pass for work almost daily.

He said he lost countless hours of work to detours and delays during the five years of construction. Now that it's complete his commutes are roughly the same as they were before construction began.

"We didn't get enough for our money," Simmons said.

The reason adding a carpool lane didn't help travel times, experts said, is a well-documented phenomenon called "triple convergence."

People who might have otherwise decided to travel by a different mode, a different route or at a different time make the decision to use the newly expanded freeway based on the assumption that it has improved. It's called "induced demand."

So even though Northbound lanes of the freeway can now handle 15 percent more traffic every hour - that many more cars are now clogging it.

Chart courtesy of Wes Marshall and Transportationist

Juan Matute, the Associate Director of the UCLA Institute of Transportation Studies said it's hard to factor in that "induced demand" when predicting traffic flows in an expansion project like the one on the 405.

"Honestly, I was doubtful that the project would provide significant congestion relief," he said.

Metro points out the project did provide relief - just not at the peak of rush hour.

"It’s natural to look at the specific time of the day when most people get off of work and get on the freeway," said Metro spokesman Dave Sotero. "But people use the 405 24 hours a day and overall we have made substantial improvements that benefit them directly."

About a fifth of the money spent on the project was secured by Representative Brad Sherman through the American Recovery and Reinvestment Act, or the stimulus bill.

Sherman advocated for the project for years, saying it was a necessary improvement to an aging freeway in need of repair.

"Success for the project was first to recognize this was never going to be a panacea," he said.

He acknowledged the limited congestion benefits of a one-lane freeway expansion but noted "this new lane’s chief contribution has been to keep things from getting worse."

In its report, released Friday, Metro said congestion would have increased 36 percent if the project hadn't been completed.

According to the study, other improvements include:

  • Congestion on surface streets around the pass, such as Sepulveda and Wilshire Boulevards dropped by 20 to 25 percent.
  • The rush hour window shrank seven hours to five. Before construction peak traffic lasted from 2 p.m. to 9 p.m. Now it lasts from 3 p.m. to 8 p.m.
  • Shorter and more consistent drive times in the early afternoon and on weekends.
  • A reduction in accidents and associated traffic delays.
  • An overall increase in the number of cars moved through the pass from an average of 10,000 cars per hour to 11,700 cars per hour.

Matute said increases in traffic generally correlate to economic activity. When construction on the Sepulveda Pass began in 2009, the country was in the midst of an economic recession. As the recovery progressed, more people began traveling for work or to go shopping or out to dinner.

He said moving more people is a social benefit in and of itself.

"When we’re moving more people," he said, "we are connecting more people with their jobs and the social opportunities for which they travel."

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