WE can no longer ignore the consequences of prohibiting heavy trucks on the 11-mile section of Interstate 580 through Oakland. While driving I-580 is safe and congestion free, the probable consequence of the ban has been to turn I-880 and Route 238 into an airborne love canal with a soaring accident rate.

From Oakland, trucks headed to the Tri-Valley and I-5 are forced onto the same freeway as those headed for Silicon Valley and Highway 101.

Consequently, the two right lanes of I-880 are jammed by heavy trucks crawling at a stop-and-go pace. At San Lorenzo, they take 238 where the congestion is even worse as they merge with traffic from the San Mateo Bridge and northbound I-880. The same problem happens in the reverse direction.

Last year, the average afternoon speed through this corridor dropped by more than 25 percent and now barely averages 20 mph. As a result, the 880-238 corridor lags only I-80 from Albany to the Bay Bridge and I-580 in the Tri-Valley as the most congested freeway segment in Alameda County.

Attempting to stay ahead of this problem, the Alameda County Congestion Management Agency has poured almost $100 million into improving the corridor, with hundreds of millions more planned, all to little avail. But the questions never asked are how much of this problem is political? How much money could be saved if the truck ban were removed? And, what is the impact on the safety and the health of the people who drive the I-880 corridor?

The truck ban goes back 40 years. Originally scheduled to be lifted in 1968, local pressure convinced then-Gov. Ronald Reagan to leave it in place.

Despite the Port of Oaklands complaints of the strain on its operations, efforts to study the ban, most recently by Caltrans in 1997, have been stymied by local officials who maintain that it is purely of local concern and their preference.

Who benefits from that preference is obvious. People living along the I-580 corridor certainly enjoy the lack of congestion and reduced noise.

Concentrating noise onto I-880 may seem logical, but a heavy price is being paid. Californias air control agency, the Air Resources Board, states that diesel exhaust contains more than 40 toxins that damage DNA and causes 250 cancers per year.

Worse, diesel exhaust is a major source of fine particulate, called PM 2.5. The 2.5 refers to the maximum diameter of the particulate in microns (millionths of a meter, 2.5 microns is 1/30th the diameter of a human hair).

The state air board estimates that PM 2.5 reduces life expectancy by 1.5 years. PM 2.5 shortens the lives of those who die from lung ailments or heart disease (including heart attacks), by 14 years. By age 18, 7.9 percent of all children exposed to high levels of PM 2.5 have permanently underdeveloped lungs, compared with 1.6 percent of the children in other areas.

While all PM 2.5 is inhaled deeply, most diesel particulate is the component of PM 2.5 that is less than 1 micron in diameter. This ultra-fine particulate or PM 1 reaches the deepest parts of the lung and dissolves the toxins clinging to it into the fluid lining the airways. One study found that children riding diesel buses to school were exposed to three times the level of ultra-fine particulate as those who walked. Other studies cited by the Air Board found that 30 to 55 percent of the average Californians exposure to diesel particulate occurs on the road, despite spending only 6 percent of their time there. Thats the average road. Imagine the dose someone gets sitting in stop-and-go traffic next to two lanes of diesel trucks on I-880 or 238.

The lower-income, non-white population along the I-880-238 corridor gives rise to civil rights and environmental justice issues that both the Congestion Management Agency and the Bay Area Air Quality Management District need to consider if the truck ban is to be maintained. The state Air Board cites studies showing that elderly people living near major highways have twice the normal risk of dying from cardiopulmonary diseases.

However, once aloft, fine particulate stays suspended for hours and drifts miles in the wind. With the prevailing wind off the Bay, the farther inland that diesel emissions take place, the less damaging they would be to the health of people of Oakland, especially given the reduced overall emissions from the better flow of truck traffic in both corridors.

Finally, the commonly realized effect of the truck ban is the fear of driving on I-880 or 238. Accidents per vehicle mile on I-880 are 50 percent higher than on I-580, having increased 25 percent over six years while those on I-580 have decreased. Accidents on Route 238 are 250 percent higher than on I-580.

The county congestion agency and the regional Metropolitan Planning Commission have begun revising their transportation plans. That planning should be done in the light of having comprehensively studied the effect of the truck ban on I-580. That study could reveal other aspects to this issue. Some say that truckers might prefer the fewer curves and hills of I-880-238. If so, lifting the ban would result in little change to the status quo. Perhaps the study will indicate that lifting the ban only during mid-day would alleviate many problems.

Even if the study reveals that the consequences of the ban are less dire than presumed, at least we will know something of the real costs of the policy and be able to say that knowledge as well as politics is guiding it.

Mark Green is mayor of Union City and serves on the Congestion Management Agency, the Alameda County Transportation Authority and the Transportation Improvement Authority. Greg Harper is a director of AC Transit and a member of CMA. From 1991-99, he served as a director of the Bay Area Air Quality Management District.