70/70A Performance

Last month I posted a table of bus performance statistics for routes in Senator Brownsberger’s district.  An sharp eyed constituent noticed that the 70/70a lagged behind its counterparts in on-time performance.  I assumed that the extraordinary length (10 miles for the 70 and over 13 miles for the 70a) of the routes, negatively impacted its on-time performance but I contacted the MBTA for the answer.

The good news is that service has actually improved since 2010:

For October 2010, weekday Route 70 was 59% on time, while all routes were 67%. For March 2014, weekday Route 70 was 63% on time, while all routes were 72%. So we are making some progress, through better scheduling which uses our GPS data, and through operations management. However, we must continue to improve.

But the length of the routes does put the 70/70a at a disadvantage when it comes to the method the MBTA uses to measure on-time performance:

The on-time performance is measured by the % of all timepoint crossings which are on time (see page 11 of the PDF version of the Service Delivery Policy). The timepoints are generally about every ½ mile on a route. In practice, a long route typically performs more poorly, since we have control mostly over the origin of the route only – we aim to schedule enough layover at the start so that the trip can depart on time about 95% of the time. After a trip leaves the origin, all of the things which cause variability kick in – boarding times, traffic, etc. For longer trips, there is greater variability as the bus gets further from the origin, but the Service Delivery Policy sets a 7-minute (or 1.5 headway) window for all midpoints regardless of how long the trip is. So you are correct that longer trips have a disadvantage, both for measuring OTP and in reality. (We could hold buses mid-route like we do with subways, and we may begin to do more of this; but the variability of buses is much greater than subways, so this won’t ever be a big part of the solution without inconveniencing too many people)

If the funding were available the MBTA may consider expanding the MBTA Key Bus Route Improvement Program to the next tier of routes. The 70/70A would be among those routes considered for improvement.

Andrew Bettinelli
Legislative Aide
Office of State Senator William N. Brownsberger

5 replies on “70/70A Performance”

  1. The problem with the 70/70A is that even if buses are running 100% on time, there will be bunching. In the AM, the timetable actually calls for a 70 and 70A to run at the exact same time (inbound at about 9 am at Watertown Square). Then there’s a 25 minute gap, and a 70 and 70A with a short headway between them, meaning more bunching, then another 20 minute gap before the next bus. The problem is that the 70 and 70A are scheduled semi-independently, when in reality most of the ridership is between the Central Squares of Cambridge and Waltham and they are effectively the same route for 90% of the riders.

  2. I have a hard time to believe the 59% on schedule time for the 70/70a bus. As annonymouse points out, often two busses come at the same time (and seem to play the elephant race that bicycle riders love so much), without improving any service. Moreover, though, the 70 bus also often comes too early. While there are apps available which tell you when a bus is supposed to arrive, what does it help if you just see it drive away. In particular in winter, I often have the problem that my app tells me that the bus is 10 minutes, away, than 5, than 1 , and then doesn’t show up at all.
    Believe me when I say that I think that riding public transport is a part of living an urban life, and one should be proud of it. However, the 70/70A do not pass muster even under the most lenient provisions for reliable service.

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