Statistical Pileup on the Freeway

When state and local transportation officials launched the one-year experiment adding two car-pool lanes, one in each direction, on a 12-mile stretch of the Costa Mesa Freeway between the Riverside and San Diego freeways, they contended that the lanes would safely move more people in less time than regular freeway lanes.

It has been six months, and the results are still questionable--in large part because of confusing data produced by the California Department of Transportation.

We still support the concept of commuter express lanes and increased car-pooling as the best available way to move people in less time on Orange County’s increasingly congested freeway system. The one-year experiment on the Costa Mesa Freeway should be completed, but it will be meaningless unless accurate statistics are produced.

Since the car-pool lanes opened on the Costa Mesa Freeway, Caltrans has claimed that the accident rate was less than before the lanes were created. Some lane opponents, organized as the Drivers for Highway Safety, insist that just the opposite was true, and have consistently challenged the state’s statistics.

Last month Caltrans released figures showing that the accident rate for the first three months of this year jumped 40% over a similar period in 1985. A week later, however, it changed the figure, revising it downward to about 6%. Then last week Caltrans admitted that the 6% accident-increase figure was too low. It now says that the accident rate (which is based on the number of accidents occurring for each million vehicle miles traveled) may be more than 30% higher than last year. But the agency just isn’t sure.

Even more disturbing than its inability to come up with an accurate figure is Caltrans’ admission that the traffic volumes that it had been using as a base in figuring the accident statistics haven’t been updated since 1982. Traffic, as anyone who drives the freeway knows too well, has certainly increased in the last four years.

Using the same traffic-volume base for so long makes all accident comparisons little more than guesswork. More than that, however, it erodes confidence in Caltrans’ credibility and makes other statistics, such as increased usage of the commuter lanes since they opened, suspect--even though they may well be accurate.

Adding to the confusion are the differences in some statistics that were submitted by staff members and then changed by their superiors. Caltrans officials say that the numbers were changed as part of “normal updating” and “adjusting for seasonal variations.”

The Orange County Transportation Commission, which meets today, is scheduled to consider ordering an independent study to try to pin down accurate safety statistics. That could help some. But as long as Caltrans remains the sole source for a lot of freeway data, the results of an independent study will be questionable, too.

The real answer is for Caltrans to keep accurate, up-to-date statistics and report them properly.

Moving more cars in less time is one of the tests that the Costa Mesa Freeway commuter lanes must pass. Doing it safely is another. The most important test for now, however, is the accuracy of the statistics that Caltrans produces for the public and its transportation officials, who must make the ultimate decision on the permanency of the commuter lanes.