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Behind the scenes with MBTA data.

The MBTA is excited to be taking many steps to improve our bus services. You can read about the process used to analyze the changes proposed by the Better Bus Project in our previous post. We're also in the beginning stages of re-designing our overall bus network. And of course, we're continuing our work to partner with cities and towns to implement street-level changes in order to prioritize the movement of buses.

Over the last two+ years, the MBTA, in partnership with cities, towns and other stakeholders, has begun piloting and implementing bus-only lanes on some of our key corridors. We will continue to partner to improve bus service by implementing more bus-only lanes as well as other interventions like queue jumps and transit signal priority.

These lanes take various forms: some are operational only during peak times, some are all-day, and they are different lengths and affect different areas. Here at the blog, we will be presenting some analysis on these lanes and all our bus priority interventions as data becomes available. Read below for an overview of the bus-only lanes we’ve introduced so far. To get an in-depth look at some of the rationale for why these lanes are so important, take a look through our bus ridership report!

The basic idea behind the bus lanes is that there are 40 or more people on a bus during peak times, and usually just one in a private vehicle, so it makes sense according to simple geometry to prioritize the travel of buses. In many cases, these lanes have taken the place of a parking lane which was only lightly used. When you separate buses from mixed traffic, you can both improve the speed of bus travel along the corridor and decrease the variability of run times, both of which make taking the bus a more competitive option with driving, and over time, you can not only improve the experience for passengers but also attract more passengers to the bus. We’ll take a look at how well these interventions have met these goals below.

1. Broadway Bus Lane, Everett

The Broadway Bus Lane in Everett operates in the inbound direction for about one mile from 4AM to 9AM, Monday through Friday. It has been in operation since December 5, 2016, though various improvements have been made since then to improve the operation of the lane. There are 5 bus routes that serve the 11 stops within the bus lane. Route 109 serves the entirety of the corridor, while routes 97, 104, 110, and 112 join the corridor at various points along the way (Figure 1). More information about the project is available on the MassDOT website.

Figure 1: Routes serving the Broadway Bus Lane in Everett

Figure 1: Routes serving the Broadway Bus Lane in Everett

1.1 Run Time Changes

To evaluate changes in run time, we used data from the MBTA’s automated passenger counter (APC) system. APCs collect information about when the doors open and close at each stop and the number of passengers boarding or alighting. Dwell times, defined here as the time in between when the doors are opened and closed at each stop, are impacted by the number of passengers boarding and alighting, whether they pay in cash or prepaid fare media, the presence of wheelchairs and strollers, and other factors. In order to focus on run times (since other programs like AFC 2.0 are intended to help reduce dwell times), the run time analysis looked at the run time between when the doors close at one stop until they open at the next stop. 

To calculate the change in run time from the bus lane, we used data from weekdays between September 1 and November 15 in 2016 and 2018. The data from 2016 represent the before condition, while 2018 represents the after condition. It is important to compare times from similar seasons, because traffic patterns vary throughout the year due to school schedules, holidays, and weather. Fall is a good time to use for comparison because ridership and traffic are generally at their highest annual levels, and travel patterns are not generally impacted by holidays and/or bad weather. 

Because various routes enter the corridor at different points, we began by looking at route 109, the only route that covers the entire corridor. We first calculated the run time for each trip in the corridor by excluding the dwell time. Next, we grouped these observations by hour and calculated the median and 90th percentile run times by hour for the corridor. The median value represents the “normal” run time for each hour of the day, while the 90th percentile is useful for MBTA operations, because each trip’s scheduled run time and recovery time is based on the 90th percentile run time. Reductions at the 90th percentile run time will have an outsized impact in vehicle reliability and the frequency at which the MBTA can operate buses.  

These results are shown in Figure 2 and Figure 3 below for the median and 90th percentile, respectively. We collected data throughout the day, but these figures show the results for peak hours when the greatest numbers of buses are in service and sufficient data was collected. While there was a clear reduction in run time between 2016 and 2018 between 5 and 9 AM, there was no discernible change during the 9-10 AM hour and the PM peak hours when the bus lane is not in operation. The savings were particularly strong from 7-8 AM, when buses saved almost 8 minutes at median and almost 11 minutes at the 90th percentile. Other routes on the corridor realized a smaller portion of the savings because they utilize a smaller portion of the bus lane. In the next section, this is considered in greater detail. 

Figure 2: Median corridor run time by hour

Figure 2: Median corridor run time by hour

Figure 3: 90th percentile corridor run time by hour

Figure 3: 90th percentile corridor run time by hour

1.2 Passenger Time Savings

After determining the run time savings, we then looked at passenger time savings, which is a function of both time saved and the number of passengers on the bus. The steps in the calculation are as follows:

  1. Calculate the median and 90th percentile run time by hour for each stop-to-stop pair in 2016 and 2018, using the methods described above. The time savings for each hour is the difference between 2016 and 2018.
  2. Calculate the average stop time and passenger load of each trip leaving each stop in 2018.
  3. Multiply the time savings times the load for each trip-stop and aggregate. 

In Fall 2018, on the median weekday morning, passengers saved 24 hours of travel time. On the 90th percentile "bad" day, passengers saved 65 hours altogether. The results by hour are shown in Figure 4 below. Passengers on routes 104 and 109 accounted for more than two-thirds of the total savings due to higher ridership and more utilization of the bus lane corridor on those routes. 

Figure 4: Passenger-hours saved per day

Figure 4: Passenger-hours saved per day

2. Mt. Auburn Street

The Mt. Auburn St. Bus Lane in Cambridge and Watertown operates in the inbound direction 24 hours a day, 7 days a week. It began operation on October 15, 2018, though there were various implementation and signal issues at first. By November 15, 2018 it began its normal operation. Routes 71 and 73 serve the bus lane. There are short bus-only lanes on Belmont Street and Mt. Auburn Street, which are served by the 73 and 71, respectively, just before the routes join together at Belmont Street at Mt. Auburn Street, as well as installed signal priority and queue jumps. From there, the bus lane continues east to Fresh Pond Parkway, though it is not continuous in throughout the corridor. More information about the project is available on the City of Cambridge’s website.

Figure 5: Map of the Mt. Auburn Bus Lane in Cambridge and Watertown

Figure 5: Map of the Mt. Auburn Bus Lane in Cambridge and Watertown

2.1 Run Time Changes

Routes 71 and 73 are served by Electric Trolley Buses (ETBs), which were the last portion of MBTA’s bus fleet to not have any vehicles equipped with Automated Passenger Counters (APCs). In July 2018, 5 of the 28 ETBs were equipped with APCs, and it took several months after installation before data was regularly collected due to configuration issues. As a result, we did not collect enough data before the bus lane installation to conduct a thorough year-over-year analysis.  The automated vehicle locator (AVL) system data was used as an alternative. It is less granular than APC data, so it is less useful for drilling down into bus lane performance, but all vehicle are tracked by AVL, offering comprehensive coverage.

To calculate the change in run time from the bus lane, we used data from weekdays between January 1 and March 31 in 2018 and 2019. The data from 2018 represent the before condition, while 2019 represents the after condition. Again, it is important to compare times from similar seasons, because traffic patterns vary throughout the year due to school schedules, holidays, and weather. Although data from Fall is preferable, the implementation and refinement of the bus lane occurred in various stages throughout October and November, making Fall 2018 a poor time for comparison. 

We then calculated the run time for the route segment between the intersection of Mt. Auburn and Belmont St and the eastern side of Mt. Auburn Hospital. This segment encompasses all of the bus lane shared by routes 71 and 73, and omits only the separate portions on Belmont St and Mt. Auburn St. before the intersection. Next, we grouped these observations by half-hour and calculated the median and 90th percentile run times by half-hour in both directions. The median value represents the “normal” run time for each hour of the day, while the 90th captures what a typical “bad day” is like. Even if a day like this only happens 1 out of 10 times, bus riders likely need to plan for the full range of possible travel times when planning their trips. Similarly, the 90th percentile is useful for MBTA operations, because each trip’s scheduled run time and recovery time is based on the 90th percentile run time. Reductions at the 90th percentile run time will have an outsized impact in vehicle reliability and the frequency at which the MBTA can operate buses.  

The inbound and outbound results are shown in Figure 6 and Figure 7 below. In the inbound direction, buses save 3-4 minutes at median and 5-8 minutes at the 90th percentile during the busiest time of the AM peak, and 0.5 to 2 minutes throughout the rest of the day. At the 90th percentile, this represents an 8-12% reduction of the maximum cycle time during the AM peak period. Despite there not being any bus lane in the outbound direction, run times were consistently shorter throughout the day, with buses saving 0.5-1.5 minutes. This is likely due in part to changes in signal timing that have helped move all vehicles through the project area. 

Figure 6: Year-over-year change in inbound segment run times on Mt. Auburn St.

Figure 6: Year-over-year change in inbound segment run times on Mt. Auburn St.

Figure 7: Year-over-year change in outbound segment run times on Mt. Auburn St.

Figure 7: Year-over-year change in outbound segment run times on Mt. Auburn St.

2.2 Next Step

Next, we will work to update these calculations as more seasonal data is collected. We also plan to estimate the savings in terms of passenger hours saved by the bus lane, though as discussed above there are some data issues that complicate this calculation. 

3. Washington Street, Roslindale

The Washington Street bus lane operates in the inbound direction from Roslindale Village to the Forest Hills MBTA Station, a distance of about one mile, from 5AM-9AM Monday – Friday. After a pilot period in May 2018, permanent operation began on June 18, 2018. Nine MBTA bus routes—30, 34, 34E, 35, 36, 37, 40, 50, and 51—operate in the corridor. More information about the project is available on the City of Boston’s website.

3.1 Run Time Changes

To evaluate changes in run time, we again used data from MBTA’s automated passenger counter (APC) system. As previously explained, APCs collect information about when the doors open and close at each stop and the number of passengers boarding or alighting. This number of passengers boarding and alighting directly affects dwell times. Therefore, in order to focus on run times (since other programs like AFC 2.0 are intended to help reduce dwell times), the run time analysis looked at the run time between when the doors close at one stop until they open at then next stop—excluding dwell times. 

Unlike the bus lanes discussed above, the Washington Street bus lane presents the ideal conditions to evaluate the bus with APC data. All buses that serve the corridor are equipped with APCs, providing a rich source of data.

To calculate the change in run time from the bus lane, we used data from weekdays between January 1 and March 15 in 2018 and 2019. The data from 2018 represent the before condition, while 2019 represents the after condition. Although data from the Fall is preferable, Fall 2017 could not be used because bus travel times were greatly impacted by road construction around Forest Hills, making it a poor choice for comparison. 

We first calculated the run time for each trip in the corridor by excluding the dwell time. Next, we grouped these observations by half-hour and calculated the median and 90th percentile run times by half-hour for the corridor. The median value represents the “normal” run time for each half-hour of the day, while the 90th percentile is useful for MBTA operations, because each trip’s scheduled run time and recovery time is based on the 90th percentile run time. Reductions at the 90th percentile run time will have an outsized impact in vehicle reliability and the frequency at which the MBTA can operate buses.  

These results are shown in Figure 8 below. There was a clear reduction in run time between 6AM and 9AM, when the bus lane is in operation, while times were very similar during the rest of the day. Buses save 2 minutes at median and 5-7 minutes at the 90th percentile during the busiest time of the AM peak. In the next section, we test how this impacted passenger and total ridership.

Figure 8: Year-over-year change in inbound segment run times on Washington Street

Figure 8: Year-over-year change in inbound segment run times on Washington Street

3.2 Passenger-weighted Savings

After determining the run time savings, we then looked at passenger time savings, which is a function of both time saved and the number of passengers on the bus. The steps in the calculation are as follows:

  1. Calculate the median and 90th percentile run time by hour for each stop-to-stop pair in 2018 and 2019, using the methods described above. The time savings for each hour is the difference between 2018 and 2019.
  2. Calculate the average stop time and passenger load of each trip leaving each stop in 2019.
  3. Multiply the time savings times the load for each trip-stop and aggregate. 

Using this method, the incremental and cumulative savings in passenger travel times is shown in Figure 9 below. In total, MBTA riders save 41 total hours of travel time at the median and 176 hours at the 90th percentile due to the Washington St bus lane per weekday. It’s possible that some of the savings calculated here may be due in part to lingering construction impacts prior to the start of the bus lane, and we will continue to evaluate year-over-year changes to confirm these estimates. 

Figure 9: Reduction in passenger-hours of travel times due to decreased run times on Washington Street

Figure 9: Reduction in passenger-hours of travel times due to decreased run times on Washington Street

3.3 Changes in Ridership

Finally, we looked at ridership in the corridor to determine whether there was any year-over-year change in ridership. During the hours of 5AM – 9AM, we found a 4% increase in ridership between Fall 2017 (3,181 arrivals at Forest Hills) and Fall 2018 (3,300 arrivals at Forest Hills). We found a similar increase of 4% between Winter 2018 (2,911 arrivals at Forest Hills) and Winter 2019 (3,034 arrivals at Forest Hills). Because there are many external factors that may impact ridership, changes in ridership cannot be solely attributed to the bus lane. However, we will continue to monitor ridership in the corridor.

3.4 Next Steps

Next, we will work to update these calculations as more seasonal data is collected. We will also evaluate the other bus lanes that are newly installed or planned for the future.