Feature: BART Shutdown Creates Unpleasant Atmosphere
As of midnight on Friday, October 18, Bay Area Rapid Transit (BART) Union workers went on strike, leaving commuters all over the Bay Area scrambling for carpools and ferry rides, and many others with the alternative of a grueling commute due to dense traffic.
After failing to settle on a contract with their employers, BART employees in Unions 1555 and 1021 announced their strike to be in effect as of 12:01, Friday morning. According to SF Gate, the BART management and unions were on the verge of an agreement Thursday evening, which disintegrated at the proposal of changing existing “work rules”.
To alleviate some of the stress put on traffic and commuters while their employees are on strike, BART is offering limited bus service to nine stations, providing rides for only about 3,000 commuters traveling round-trip, though their usual daily estimate is 200,000.
While the strike elicits support, as it seeks to improve workers’ salary and work environment, and criticism (mostly for inconvenience) from riders and officials, the additional pollution from the drastic increase in the number of commuters on the road adds to the already-existing atmospheric haze over the Bay, leaving commuters and environmentalists thankful for the Bay’s public transit systems.
As reported by KQED, “the Census Bureau reports the San Francisco-Oakland-Fremont metro area has more workers than anywhere else in the country who travel at least 50 miles and 90 minutes (one way) to work.” The environmental dilemma brought about by the absence of public transport, on which commuters are dependent, is formidable: more drivers means longer commute times, which means more fuel consumption and pollutants released.
With 200,000 riders displaced from BART, a large percentage of whom have resorted to driving personal vehicles, the pollution levels in the Bay Area’s atmosphere have risen, and are sure to remain at higher levels as the strike continues, as the combustion of hydrocarbon fuels emits significant amounts of compounds, which, in large quantities, contribute to atmospheric pollution.
The emitted particles that are most prevalent include volatile organic compounds (VOC), mono-nitrogen oxides (NOx), particulate matter (PM, primarily released by heavy-duty diesel vehicles), carbon monoxide (CO), and carbon dioxide (CO2).
The EPA’s computer model, MOBILE6.2, provides calculated emission rates of these pollutants when vehicles are both idle and traveling at an average speed of 40mph, including the impact of variant acceleration patterns.
In its report, the EPA claims that a light-duty (less than 6000 pound) gasoline-fueled passenger vehicle emits 1.19 grams of carbon monoxide per minute while idle, and 7.9 grams per minute while driving. Emissions of both NOx and total hydrocarbons fall at about .05 g/min, and about 19 pounds of CO2 is released per gallon of gas combusted.
Those values may not seem extreme, but consider this: if approximately 190,000 employees commute in personal vehicles round-trip as a result of the strike (not including the 3,000 people provided BART bus transit from the usual 200,000 travelers, and allowing that 7,000 others may telecommute, bike, or travel by other means), and supposing that 10% of them will carpool with one other person, that amounts to an additional 180,500 cars on the road per day without BART services.
Suppose, then, that the commute time (one way) of those 180,500 cars will average at one hour, halfway between the common 30 minute estimate-by-zip-code offered by the interactive map below, and the Census Bureau’s 90 minute estimate. Due to traffic, we’ll also suppose that each car will spend at least a tenth of its travel time (6 minutes) idling.
To estimate and analyze the volume of added pollutants to the atmosphere during the interval without BART services, I produced a spreadsheet to calculate per-car emissions of NOx and CO, through the duration of a variable commute time.
By calculation, each day that the BART transit system is not running, an additional 345,000 pounds (rounded) of carbon monoxide and 27,500 pounds of nitrogen oxides are released into the atmosphere.
Values highlighted in yellow may be altered to produce different resultant values, highlighted in steel blue. Manipulate the spreadsheet to produce values of estimated emissions per commuter, by entering a unique commute time or by replacing other values highlighted in yellow.
The estimated emissions for the approximately 200,000 displaced commuters doesn’t allow for the level of pollution from the BART transit system itself, which at peak hour, is “12 times more efficient on a passenger miles per gallon basis than a typical single occupant vehicle,” (as reported in their Green Factsheet) or transportation to and from the BART terminals.
Ultimately, these estimations have been determined by values borrowed from external calculations and rely on assumptions of commuters and commuter patterns suggested by figures offered by BART and other sources. Consequently, the actual difference may be smaller than the estimated values given. However, even considering these variations, the calculated volumes of additional pollutants are significant, and striking.
Hopefully a settlement will be reached soon, eliminating the external costs of the suspension, and the Bay Area’s metropolitan system may unite to further establish methods of environmentally conscientious and efficient systems of public transport.
Below is an interactive map of average commute times by zip code, provided by WNYC, a division of New York Public Radio.