But to terrorism experts, emergency officials and chemical hazard researchers, they are lurking weapons of mass destruction, waiting for mishap or sabotage to set them off.
At a U.S. Senate hearing Jan. 18 the problem of highly hazardous chemical rail tankers in urban areas was listed as the Transportation Security Administration's second biggest threat to surface transportation, after direct threats to passenger rail systems that travel beneath the ground or water.
More than 100,000 tankers full of toxic inhalation hazard chemicals, such as chlorine and ammonia, are shipped through the nation annually out of a total of about 1.2 million tankers carrying materials considered hazardous in varying degrees.
On any day, one can see the tankers lumbering through communities such as Berkeley, Fremont, Redwood City or South San Francisco. Passengers at the Emeryville Amtrak Station often find the tankers sitting idle between the depot's platforms and a shopping mall across the street.
The side of the cars are often marked with taggers' spray-painted calling cards, exposing the extent to which the deadly cargo is vulnerable.
The juxtaposition of the Bay Area's densely populated Bay-side neighborhoods with pressurized tankers of poison gas like ammonia and chlorine and highly explosive chemicals like liquid petroleum gas used to be something officials could do little more than wring their hands over.
Now, however, they are looking to the nation's capital, to a politically shifted Congress and an executive branch under pressure to take action five years after the Sept. 11, 2001, attacks transformed the issue from a safety and ecology debate to a national security imperative.
But five years later, the Federal Railroad Administration has only one full-time employee working on security for the nation's entire 142,000-mile passenger and freight rail network.
Anxious about the unabated threat posed by the potential chemical warheads in its midst, the District of Columbia city government defied the Federal Railroad Administration and passed its own safeguards for such shipments. Other, more industrial cities, such as Chicago, Buffalo and Baltimore, are poised to follow the district's example. The district ordinance has been tied up in federal courts since it passed in 2004, opposed by railroads and the Bush Administration.
But in December, two federal agencies proposed new regulations they say would better supervise parked tankers and for the first time consider re-routing hazardous shipments around potential terror target areas.
"This has been an issue of concern for us for many, many years," said Nora Davis, mayor of Emeryville, where chemical tankers often sit idle and unprotected next to shopping centers, hotels and apartment blocks. "Finally, people are taking a serious look at this. It's past time for a concerted effort to regulate this."
The issue has been around for decades, starting as a safety and environmental concern. Chemical plants and other facilities using hazardous materials were the main targets of this attention, culminating in the 1999 release of federally mandated "worst-case scenarios" aimed at preparing local authorities for toxic emergencies.
After the Sept. 11 attacks, the specter of deliberate attacks on chemical tankers became the focus of regulatory efforts. Environmental activists armed with photos of 90-ton tankers of chlorine used as a weapon in World War I passing near the U.S. Capitol spurred passage of the District of Columbia ordinance, which required such shipments to be re-routed away from the city's center.
Bay Area officials are also concerned that the recent trend to focus new development in urbanized, formerly industrial areas will put even more homes and shops in harm's way.
"We have rezoned quite a bit of land along the waterfront, for housing, for transit-oriented development, which is supposed to be a good thing," said Martinez Mayor Rob Schroder, who envisions the new developments as a place where residents will have easy access to buses, Amtrak passenger trains and ferries to San Francisco.
And the freight trains that rumble through the town at all hours along the nation's first transcontinental railroad are so much a part of the town that they have become background noise for many residents.
"Every once and a while, we think about and talk about safety, but rarely to do we talk about terrorism because we know how much of a potential for a very bad incident there could be," Schroder said. "It's almost like we don't want to think about it."
Just outside of the Shell Oil refinery in Martinez, rows of liquid petroleum gas tankers regularly wait to be hitched to trains. Anyone journalist, graffiti artist or saboteur could get close enough to tamper with the parked tankers without railroad security or the thinly stretched Transportation Security Administration officers asking any questions.
Problem outside the gates
Since Sept. 11, access to hazardous chemicals at fixed facilities has been tightened, such as the installation of a new high-tech surveillance system for the Port of Oakland. The problem, security advocates complain, exists just outside the gates.
"What sense does it make to put guns, guards and gates around these factories, and then open the gates and ship their most dangerous poison gas cargoes in huge quantities right through the target cities?" asks Fred Millar, an activist with the environmental group Friends of the Earth. "Why don't we pre-position huge quantities of aviation jet fuel on the tops of all of our tallest buildings? That way, the terrorists wouldn't have to go through the inconvenience of flight training."
Millar has mounted a crusade to reroute chemical shipments, phoning fire officials, legislators and journalists in cities across the country, leading video forays into rail yards to document lax security around chemical cars.
Such activism has irritated railroads like Union Pacific, who maintain that their safety record, with hazardous freight arriving without incident 99.98 percent of the time, is a model for other industries. The industry's close regulatory relationship with the federal government makes them an ideal partner to help secure the nation against terrorist threats.
But they acknowledge that people can get near the tankers, which, unlike tanker trucks, can't be regulated by states or local governments.
"People do. We know they do. The key is having eyes and ears, to have people ... watch," said Mark Davis, a spokesman for Omaha-based Union Pacific, which owns much of the rail right-of-way in the Bay Area. "Trespassing on railroad property is dangerous. Reporters and the general public, unfortunately, after 9/11, to make a point, they would come on the railroad property and claim that the industry was not safe.
"If you're going to watch, do it from a public street," Davis cautioned.
Safety authorities, however, are unimpressed with the railroads' vigilance.
"If there were no security on-site, all you would have to do is walk up to one of these cars and disable a valve so that it was stuck in the open position and walk away," said Philip White, chief of the South San Francisco Fire Department. "You just need bolt-cutters."
Safety officials from South San Francisco to South Carolina, where a chlorine tanker crash and release in January 2005 killed an engineer and eight factory workers, complain that the railroads often won't tell them what is going through their neighborhoods.
After discovering tankers in his city loaded with highly flammable solvent toluene, White supported an unsuccessful effort last spring to pass a state law requiring shippers to pay a hazardous substance fee that would help pay for the equipment and training necessary to deal with the consequences of a release, fire or explosion.
And those consequences could be catastrophic, said Ron Koopman, a chemical hazard researcher who retired in 2003 from Lawrence Livermore National Laboratory.
Liquid petroleum gas, also called propane, sits in strings of black tanker cars on sidings between the Bay shore's refineries from Richmond to Martinez and beyond.
A ruptured car could lead to something safety experts call a BLEVE (pronounced "blevy") boiling liquid expanding vapor explosion said Koopman, who actually ruptured chemical tanker trucks at a nuclear weapons test site in Nevada to record the results.
"A really big release outside can explode," Koopman explained. "The fire would heat the other propane cars until they explode, and that creates a huge explosion."
Koopman said he believes LPG is even more dangerous than the controversial liquid natural gas, which environmental activists have staged a high-profile campaign against bringing to California.
New rail couplers and steel plates have reduced the chances of an accidental rail car puncture, he said, but would not stop an act of sabotage.
On Jan. 16, federal railroad officials, freight, chemical and tanker manufacturing company executives announced a new partnership aimed at developing a safer rail tanker, one less vulnerable to crashes and perhaps even some forms of terror attacks. That very day, a derailment near Louisville, Ky., confounded efforts to bring a cocktail of burning chemicals under control. The freight line that derailed, CSX Transportation, was the same one suing to neutralize the District of Columbia ordinance.
While cities in the East have actively sought greater tanker car restrictions, Millar said the effort is just stirring in California.
"This is really a statewide problem, particularly in the Bay Area, where they're using the siding track" to store tankers, said White, who urged his counterparts in other Bay Area jurisdictions to inspect their local sidings. Many were surprised to find parked hazardous tankers, he said.
White and others who have confronted railroads have found themselves up against powerful railroad, chemical and oil interests with many allies in both Sacramento and Washington.
U.S. Rep. Tom Lantos, D-San Mateo, decided against pursuing a legislative or regulatory solution to White's complaint, but instead convinced Union Pacific and its shipping customers to deal with the complaint locally, said Lantos spokeswoman Lynn Weil.
"Tom found a solution by just talking with the companies," Weil said, that included providing training and equipment for the fire department and working on alternate shipment routes.
But with the Democrat-controlled Congress elected Nov. 7, that dynamic has already begun to change.
At the Jan. 18 Senate Commerce, Science and Transportation Committee hearing, senators chided federal security and railroad officials for using only a small fraction of security resources for protecting surface transportation, as opposed to air travel.
Among several bills being considered by the new Congress is a bill similar to one sponsored last year by Sen. Joseph Biden, D-Del., that would require such shipments to be re-routed around major population centers and any areas considered likely terrorist targets. That bill never made it out of the Republican-controlled Senate Commerce, Science and Transportation Committee last year, but is expected to do much better this year.
Regardless of what may come with the new Congress, local emergency officials will continue to keep a wary eye on the hazardous shipments.
"Would it cause me concern? Yes. Would I make an inquiry? Yes," said David Orth, deputy fire chief in Berkeley, another city along hazardous cargo routes. "If I were getting on the train at the Emeryville station, I'd wonder about it."
Contact Erik N. Nelson at email@example.com or (510) 208-6410. Read his transportation blog at InsideBayArea.com.