They might not be big enough to swallow a Mini Cooper, but the deteriorating conditions on westbound Oregon Expressway near U.S. Highway 101 have become such a hazard for motorists that the City of Palo Alto decided to repair them this week, even though the section of roadway is owned by the state.

Nearly a dozen dinner-plate-sized holes, some more than 2 inches deep, have forced drivers to swerve or to hit them with a tooth-jarring clatter.

The potholes, which city transportation officials said have been enlarging for a month, are the responsibility of state transportation agency Caltrans. Most of Oregon Expressway is under Santa Clara County jurisdiction, but the two-block area adjacent to the freeway is state-owned property -- hence neither the county nor the city have responsibility for fixing it.

Caltrans on Monday alleged that it had already fixed the potholes. In response to a citizen complaint filed online on Feb. 16, the agency on Feb. 22 stated the repairs were completed.

"Your concern as submitted on the Maintenance Service Request has been addressed, and your ticket has been closed," the agency wrote in an email.

But the fixes were not apparent as drivers continued to dodge into the expanding holes earlier this week.

The worsening problem prompted City of Palo Alto Public Works officials to declare the conditions an emergency, and workers filled the potholes on Wednesday after being alerted by the Palo Alto Weekly.

"Our Public Works department has determined an emergency repair is necessary immediately on the potholes, and we will dispatch a crew as soon as possible. We expect a repair to be completed by the close of business, this afternoon," city spokeswoman Claudia Keith said in an email on Wednesday afternoon.

She assumes the city will send Caltrans an invoice for the work, she added.

The Palo Alto Public Works Department provided a photo of their crew fixing the holes Wednesday.

Meanwhile, Caltrans spokesman Bernard Walik said on Thursday morning that the agency is also working to fix the problem after receiving calls from the city. The work should be done by the end of day on Thursday.

He said that state workers may have fixed a pothole on a different stretch of the road, thinking that was the pothole mentioned in the citizen complaint, thus the maintenance ticket was closed. It's a frequent problem, he said. Employees do patrol roadways for defects, but they don't catch everything because of the thousands of miles of roadway they must cover, he added.

Caltrans faces a bigger problem based in part on funding and in part on human behavior, he said. A spike in the number of homeless encampments and the amount of litter deposited by the general public in recent years is causing personnel to shift their time away from infrastructure repairs to addressing these other concerns. The problems are significant resource wasters, he said.

Caltrans doesn't remove the encampments, but it must wait for police to do so before the agency can clean up the site, he added.

But years of underfunding by the state is perhaps a larger problem, California Gov. Jerry Brown's office acknowledged in its 2016-2017 Governor's Budget.

"State funding has fallen dramatically below the levels needed to maintain the system. Annual maintenance and repair needs on the state's highway system are significantly more than can be funded within existing resources, with a current identified funding gap of almost $6 billion annually," the budget summary noted.

Given the shortfall, maintenance of critical structures such as bridges, emergency, safety and pavement preservation takes precedent, according to the 2015 Ten-Year State Highway Operation and Protection Program Plan. But the percentage of pavement in distressed condition, which is pavement with significant rutting, cracking and potholes, is expected to increase, the report noted.

The costs to drivers of the public are not insignificant. A recent transportation study found that Californians spend an average $762 annually on vehicle repair costs due to poorly maintained roads, according to the budget summary.

The portion of Oregon Expressway from Bryant Street to West Bayshore Road, which is owned by Santa Clara County, was the subject of a $3.5 million pedestrian-and-bicycle-improvement project that was completed in 2014. It included new traffic signals, some intersection reconfigurations, new road striping, and curb and road resurfacing. It did not include Caltrans' roughly two-block area of the expressway west of Highway 101 between Carmel Drive/West Bayshore Road and the freeway.

Michael Murdter, director of the Santa Clara County Roads and Airports Department, said in an email that the project engineer on the Oregon Expressway Project did coordinate with Caltrans, but it was mainly regarding traffic control during construction, not about adding pavement work in Caltrans' jurisdiction.

The county is developing plans to upgrade its entire expressway system, which includes other parts of Oregon Expressway from Bryant Street and up Page Mill Road to Interstate Highway 280.