MBTA Healthy & Sustainable Transportation

The expansive service and prominent regional position of the MBTA means it has significant potential to alleviate congestion and mitigate greenhouse gas (GHG) emissions from single-occupancy vehicles through mode shift — trips taken on transit that may have otherwise been taken by car. Measures such as ridership provide context for mode shift, while GHG emissions reductions and bus electrification efforts work to advance healthy and sustainable transportation in the region.


Ridership measures the number of rides the MBTA system provides each year. In accordance with industry standard, ridership is measured as unlinked passenger trips (UPT), which reflect each time a passenger boards a transit vehicle. Unlinked passenger trips include estimates for trips that are not directly measured, such as transfers that do not involve fare equipment and trips in which riders do not interact with the fare system. Ridership estimates for FY23 may be adjusted slightly in the future.

Riders completed a total of 233.1 million unlinked passenger trips across all MBTA services in FY23, or roughly 752K UPT on an average weekday. This represents a 14.8 percent increase from 203 million UPT in FY22, which is a significant increase but still 35.8 percent lower than the 363 million UPT seen in FY19. All modes increased ridership in FY23 compared to FY22. Bus service retained the highest proportion of total ridership at 37 percent, and increased UPT by 12 percent in FY23 over FY22. Other modes of transportation also increased ridership. Ferry ridership increased by 67 percent from FY22 to FY23. Heavy rail ridership increased by 6 percent, light rail increased by 23 percent, Commuter Rail increased by 57 percent, and the RIDE saw a 17 percent increase in ridership.

Ridership estimates for FY22 may be adjusted slightly in the future. Ridership may not match annual and monthly ridership estimates reported to the National Transit Database (NTD) due to new data that may become available after reports are submitted, such as from Green Line vehicles. The most current ridership estimates can be found on the MBTA Performance Dashboard.

Greenhouse gas (GHG) emissions are reported as the MBTA’s total GHG emissions in kilograms of carbon dioxide equivalent (kg CO2e) and as the rate normalized by total unlinked passenger trips (UPT). This measure does not account for GHG savings acquired via mode shift, from trips taken on transit rather than in single-occupancy vehicles, which is estimated to be at least four times larger than net emissions.

In FY23, the MBTA emitted 237.8 million kg CO2e, a 2.6 percent decrease from 244.2 million kg CO2e in FY22. The Commonwealth of Massachusetts aims to reduce GHG emissions by 80 percent by 2050 compared to 2005 levels, and the MBTA is on track to meet that goal. In FY23, the MBTA made headway towards this GHG reduction target, reducing GHG by 43.8% from a 2009 baseline. The MBTA is still committed to Net-zero by 2050. The rate of GHG emissions was 1.02 kg CO2e per UPT in FY23, a 15.4 percent decrease from 1.21 in FY22.

Bus fleet composition measures the proportions of the MBTA bus fleet that are electric, hybrid, utilize compressed natural gas (CNG), or diesel fuel sources. Buses classified as electric include battery-electric buses, while buses classified as hybrid — with both electric and conventional fuel options — include traditional hybrid buses and Dual Mode Silver Line buses. In FY23, the MBTA’s roughly 1,069-bus fleet was 0.5 percent electric, 65.2 percent hybrid, 16.3 percent CNG, and 18.0 percent diesel.

Bus fleet composition particularly impacts residents living near bus routes due to air pollutants emitted. While diesel-only buses emit higher levels of criteria air pollutants, alternative fuel buses (including electric, CNG, and hybrid) can mitigate air pollution caused by buses for nearby residents. Of residents living within a quarter mile of MBTA bus routes in FY23, roughly 47 percent were near routes running alternative fuel vehicles, 44 percent were near routes running vehicles of mixed fuel types, and 9 percent were near routes running diesel-only buses. For low-income households within a quarter mile of MBTA bus routes, roughly 38 percent were near alternative fuel routes, and 13 percent were near diesel-only routes. For the purpose of standardization, low-income households are defined as a household earning less than $82,000 per year. Of residents of color living near MBTA bus routes, 55 percent were near alternative fuel routes and 10 percent were near diesel-only routes.