Concerned that Caltrans has used inaccurate data to defend the controversial car-pool lane experiment on the Costa Mesa Freeway, county transportation officials said Thursday that they will ask for an independent study to resolve the safety issue.
"When you change numbers as often as Caltrans has, it certainly damages their credibility," said Stan Oftelie, executive director of the Orange County Transportation Commission, which endorses the car-pool lanes. "We have great concern for the credibility of the numbers."
The car-pool lanes, limited to vehicles carrying two or more people, stretch 11.8 miles between the Riverside Freeway (Route 91) and the San Diego Freeway (Interstate 405), and run both northbound and southbound. The lanes were opened last Nov. 18, first for a 90-day trial, and then for another nine months.
Conflicting Accident Data
Since the car-pool lanes opened, the California Department of Transportation has insisted that the accident rate on the Costa Mesa Freeway has declined in comparison to the rate before the lanes were installed. This was the department's position as recently as June 16.
Then on June 23, a Caltrans official released figures showing that the accident rate for the first three months of 1986 was 40% higher than the rate for the same quarter in 1985. Within a week, however, Caltrans said the reported increase was far too high, that the actual rate was up only about 6%, a barely useful figure since accident rate calculations involve a possible plus or minus 5% error margin.
But this week Caltrans officials admitted that the 6% was too low--that it was based on traffic volumes that had not been updated since 1982, making comparisons with 1985 "invalid" without additional, educated guesswork to fill in the gaps.
Now Caltrans officials are saying the accident rate for the first three months of 1986 may be more than 30% higher than the rate in the same 1985 period, but they are not sure.
Freeway System Rate
Meanwhile, Caltrans has provided separate figures showing that the accident rate for the "urban freeway system," which involves 608 miles of freeways in Orange, Los Angeles and Ventura counties, increased about 7.8% between 1984 and 1985. The accident rate is based on the number of accidents occurring for each million vehicle miles traveled.
Caltrans officials said they were surprised by the call for an independent analysis but admitted major errors in their accident rate calculations.
However, "we feel we've been responsible," said Chuck Boyer, Caltrans's senior operations engineering analyst in Los Angeles and a veteran of the ill-fated Diamond Lane experiment on the Santa Monica Freeway 10 years ago. "We have given any data anybody has asked for as best we can. When we have discovered errors, we have notified all the parties as soon as was practical. But we would have no objection to an independent study. . . . It might be the prudent thing to do."
Caltrans and county reports have shown that the car-pool lanes have helped the Costa Mesa Freeway move more people faster. But when asked how much of an increase in the accident rate is acceptable as a trade-off for improved mobility, both Caltrans and county transportation officials said Thursday that they did not know.
"That's a decision for policy makers, for politicians," Boyer said.
"We have no set standard for that," Oftelie said.
A six-month progress report on the commuter lanes will be presented to the county commission at its meeting Monday, and James H. Beam, a Transportation Commission member who has been a strong supporter of the lanes, said he will formally request the independent analysis to resolve the safety issue. Oftelie and Beam said the request will be unopposed.
"I don't think Caltrans has been up to any kind of trickery, but it's clear that some of their numbers are based on incorrect information," Oftelie said .
"Early on they (Caltrans officials) kept saying the accidents were down, and now that appears not be the case," said Beam, chairman of the subcommittee that has monitored the car-pool lane experiment. "We have to get some numbers that are accurate," he said.
Commission sources said the panel will try to negotiate a contract for less than $10,000 with the Institute for Transportation Studies at UC Irvine. Institute officials were unavailable for comment.
State and county transportation officials acknowledged that the move for an independent study enhanced the credibility of Drivers for Highway Safety, a grass-roots citizens group that has long criticized the car-pool lanes as unsafe because there is no barrier separating them from much slower moving traffic, from which cars weave in and out.
"I'm glad they're finally admitting some mistakes have been made," said Joe Catron, a founding member of the group.
Although they support an independent analysis, county officials are not expected to terminate the car-pool lane experiment and open the lane to all motorists as demanded by the citizens' group.