A new report reveals the slowest MBTA bus route in Boston — and it averages 6 mph

Local News

A new report from Transit Matters shows the top 10 slowest and top 10 most bunched routes.

The SL4, a Silver Line that travels between South and Nubian Stations, won the not-so-esteemed honor of slowest MBTA bus route, according to a new report.

Transit Matters, a Mass. transportation advocacy nonprofit, found the route traveled at an average speed of 6.09 mph in October 2025 — a trend of Boston’s slowest routes getting even slower.

The third annual report analyzed publicly available bus data to reveal the top 10 slowest and top 10 most bunched bus routes. Each report has used the previous October as a sample for a “faithful” year-over-year comparison, according to the report.

The top 10 slowest bus routes in Boston recorded an average speed of 6.42 mph, which is a drop from 6.83 mph two years ago, according to the report. 

However, it’s not all bleak. 

The report found that the MBTA’s top 10 most bunched routes — routes with the highest percentage of buses arriving together as opposed to evenly spaced apart — are improving. The average bunch rate for the top 10 routes is 13.9 percent, which is down nearly two points from last year, the report found.

“Traffic-slowed and blocked buses impact the daily lives of riders by introducing uncertainty into their schedules and costing them time with loved ones,” the report says.

Seven of the slowest routes from last year’s list found their way back onto this year’s list, while eight of the most bunched routes repeated, according to the report. Many of these routes travel through Black and brown communities and low-income neighborhoods, the report says.

“Poor bus service is not just an issue of inefficiency; it is an issue of opportunity, mobility, and quality of life for these communities,” according to the report. “Inefficient service is felt every day by riders who may have to wait fifteen minutes longer in the extreme heat or cold.”

The report comes at a time when the city plans to expand bus lanes and transit signal priority, along with the addition of bus-mounted enforcement cameras to fine vehicles stopped in bus lanes. However, the report says several bus infrastructure projects have slowed.

Some of the potential solutions suggested by the report are continuing the city’s progress on projects, such as ones along Hyde Park Avenue and Blue Hill Avenue, as well as reinstating bus lanes on N. Washington Street and Boylston Sreet after they were removed.

Slowest bus routes

The SL4, which takes the crown for slowest route of the year, saw a decline in speed of nearly 0.8 mph over the last three years, according to the report.

The 1 bus, which travels between Roxbury and Harvard, earned runner-up with an average speed of 6.2 mph. The 93 bus, 47 bus, and CT3 bus all round up the top five slowest routes in the city. 

Other buses included in the report’s list are the 92, 66, SL5, 19, and 10.

Seven of the top 10 slowest buses service Roxbury — a community with a median household income of about $46,000 and nearly 39% without access to a car, the report says.

Top 10 slowest MBTA bus routes, according to Transit Matters:

1. SL4
2. 1
3. 93
4. 47
5. CT3
6. 92
7. 66
8. SL5
9. 19
10. 10

Most bunched bus routes

The 32 bus owns the top spot in the most bunched bus routes, with a 17.1 percent bunching rate. The bus, which travels between Hyde Park and Jamaica Plain moved up from the fifth spot last year and increased its bunching by 2 percent, the report found

The 116 bus, which travels from Revere to East Boston, shot up from an unranked position last year to the No. 2 spot. The report says the rise in bunching might be due to the 117 bus dissolving into the 116, which led to an increase in frequency. 

The 1 bus and the 66 bus, which travels from Roxbury to Harvard, earned places in both lists, according to the report. The 39, 22, 31, 57, 23, and 111 complete the list for most bunched bus routes.

Three of the most bunched routes once again service Roxbury, while another three go through Dorchester, according to the report.

Top 10 most bunched MBTA bus routes:

1. 32
2. 116
3. 1
4. 39
5. 66
6. 22
7. 31
8. 57
9. 23
10. 111