Not Your Imagination: Quantifying #ClumpMetro
Ever since MetroRapid received significant frequency increases at the end of last summer (every 10 minutes on weekdays; every 15 minutes on weekends), Austinites have noticed a lot more bus bunching on the 801 and 803.
Some no-name local transportation journalist dubbed the phenomenon #ClumpMetro. But is it real, or just a social media fad without merit? This wannabe journalist with some programming skills decided to find out.
I wrote a Python program that records Capital Metro bus arrivals at select stops. It uses the agency’s open data portal to retrieve arrival predictions. When an individual bus gets dropped from the list of predicted arrivals, the program records an arrival event for that bus line.
I turned my program loose on five 801 stops in the northbound direction to get to the bottom of the bunching:
- Little Texas
- Oltorf
- Capitol
- Triangle
- Rundberg
I chose these stations to get a good sense of MetroRapid’s performance along the entire North Lamar/South Congress corridor.
As we all know, MetroRapid does not have a conventional timetable, just certain headways the service aspires to throughout the day. For my analysis, I used the number of minutes between each arrival as a measure for tardiness. If that interval is greater than the published headway, the second bus is running late.
Here’s what I found.
These visualizations were inspired by the recent Human Transit post on transit reliability.
As you can see, it’s not just you: MetroRapid only adheres to its published headways about 60–75 percent of the time.
Geography-wise, reliability gets progressively worse the further north you are along the 801’s route. This makes sense because you’d expect the buses to depart from their Southpark Meadows terminal with reasonable spacing, then lose that spacing as they proceed further down the line.
How about reliability over the course of the day?
Here’s a sample of data from Triangle Station. It includes the recorded headways for an entire Thursday and part of a Saturday (unfortunately, the program crashed during collection).
It appears most of the bunching occurs at mid-day; evenings and weekend mornings seem relatively reliable. That’s all the more reason to publish proper timetables for these time periods, when MetroRapid operates at non-frequent (>15 minutes) intervals.
But unfortunately, the data show some gaping gaps in service. In some cases, an 801 doesn’t arrive for over 25 minutes during periods when the frequency is supposed to be every 10 minutes.
How about conventional MetroBus lines?
I wondered whether a conventional bus line like the 7, which is operates every 15 minutes on weekdays, would show some improvement compared to MetroRapid. Assuming there’s enough slack in the timetable, the schedule would trade speed for increased regularity.
I observed route 7 arrivals at 11th/Congress for several hours, and I still found long gaps and bunching in the morning.
So a schedule wouldn’t save us either, unless it had so much padding that the bus waits for minutes on end at each timepoint.
This has implications for the Cap Remap bus network redesign, which will drastically expand frequent service. Expect lots of bunching on MetroBus after June, particularly in the first few months before Cap Metro nails down the travel times on the new routes.
That leads us to our next question.
What can Cap Metro do about this?
Well, not much.
Since MetroRapid is always stuck in some sort of traffic — even in the downtown transit lanes, where it contends with cyclists and other buses — it’s an inherently unreliable service.
Implementing bus lanes and queue jumps at chokepoints like the Drag and the First Street Bridge could help, to some extent. But the difficult truth is, transit needs dedicated guideway along its entire route to stay regular. In other words, until Project Connect puts reserved rail and BRT lanes on Austin streets (fingers crossed), this is going to be the status quo.
That’s not to say there’s nothing Cap Metro can do.
If a MetroRapid bus is running late, the agency could “short-turn” that bus by asking it to turn around before the end of the route. That puts the bus back on schedule but requires all passengers to get off and wait for the next one. Alternatively, Cap Metro could tell the following buses to hold at their stops and/or drive slightly more slowly. Some MetroRapid drivers already do this of their own accord.
Making use of either solution would undoubtedly anger the agency’s customers, who have little patience for even the slightest of delays.
So Cap Metro has, understandably, acted conservatively. I have never seen the agency short-turn a MetroRapid bus, but they say they occasionally do it.
Props to Cap Metro for making their arrival information public, because this is really interesting data. I’m sure interested advocates could come up with all sorts of research questions, and it would also be possible to build a real-time visualizer like TransitAlliance did in Miami.
The takeaway from this small study is that Cap Metro should consider micromanaging MetroRapid a little more aggressively. Also, that bunching is a constant reminder Austin really really really needs fixed guideway transit.
Until that ever happens, long live #ClumpMetro.
