After more than four years of construction, $1 billion, two "Carmageddons" and a Jamzilla, a notoriously traffic-choked stretch of the San Diego (405) Freeway has a new carpool lane but not a whole lot of relief to show for it.

Average travel time increased by one minute on a 10-mile stretch of the 405 connecting Los Angeles' Westside with the San Fernando Valley, jumping from an average of 34.5 minutes last September to 35.5 last month, according to INRIX, which studies traffic data.

Even Los Angeles Mayor Eric Garcetti, who assumed office in July 2013, admits he had reservations about the I-405 Sepulveda Pass Improvements Project on the busiest urban highway interstate system in the country.

"I'm glad I could accelerate it as mayor when I came onboard and inherited this project, but if I was starting from scratch I would have done it differently," Garcetti said.

Officials had expected the project to shave about 10 minutes off the average commute on a stretch that sees more than 350,000 cars daily.

But some drivers have a perennial migraine.

"It’s still really congested so I wouldn't say it got any better," said commuter Drew Gosselaar.

Analysts at INRIX attribute the 405 commute time flatlining to more motorists driving due to better gas prices, more people getting back to work and an overall increase in congestion, according to Jim Bak, an INRIX spokesman.

Officials with the Los Angeles County Metropolitan Transportation Authority say they hope to cut travel times in the area for bus riders with a new express bus to debut later this year.