Under the Clean Diesel Bus Program which began in 2003, these "high-tech emission control filters" prevent over 50 tons of harmful particulate matter and 436 tons of nitrogen oxides (NOx) from being released into Bay Area air each year.
At a cost of $18,000 each, the filter-fitted buses, which have years of service ahead of them, provide a reasonable alternative to new buses which come in around $140,000. The program is being funded by the Air District, MTC and the regional transit districts.
As of last Tuesday, 1,384 buses have undergone the treatment with 340 left to go. Most of the remaining buses are scheduled to go under the knife by the end of this year.
[Source: Metropolitan Transportation Commission]