One Weird Trick Transit Agencies Might Use to Make Your Ride Faster

-
Hey, transportation planners, want to improve the speed and reliability of your bus or light rail network?

If so, consider the noble termite.
I don’t mean mimic termites’ rapacious appetite for historic bungalow basements, or their ability to build an England-sized network of mounds visible from space, even though those are both compelling potential transit improvements that could be considered down the road. No, what I’m talking about is a concept called “stigmergy,” by which eusocial creatures (termites, ants, etc.) communicate with each other via modifications to the physical environment in a self-organizing system of stimulation and response.
“Huh?” you’re saying to your computer monitor. “What does this have to do with transit?”
Well, it has to do with the increasing interest around automated vehicles (AVs), and how these technologies can be applied to improving transit systems plagued by interruption and delay. A 2017 paper by a team of researchers from the National Autonomous University of Mexico looked at a novel way to improve transit reliability by incorporating stigmergic principles into a hypothetical AV transit system (Carreón, 2017). In their model, trains (and this model would only work on trains or BRT with a fully protected right of way) would essentially only communicate with the following and preceding trains, telling each other when they left a station and how soon they think they’ll arrive at the next one.

Imagine that you’re on one of these hypothetical trains. As you leave the station, your train leaves behind a marker of sorts (the paper uses the very evocative term “anti-pheromone”) telling the train following yours what time it left the station, and it also radios to the train ahead of it how far behind you are. When your train pulls into its next stop, it receives a message from the train ahead saying, for example, “I left this station at 100 seconds ago.”

The model uses this intercommunication between trains to create a decentralized rule set that, using a vast simplification, dictates that trains must leave the station when the “time gap” between them and the train ahead is greater than the “time gap” between them and the train behind. Various extensions to the algorithm allow the trains to account for sudden stoppages along the line, speeding up or slowing down if necessary, but always endeavoring to maintain an even spacing between vehicles - like ants marching along a branch.
This strict, insectoid-inspired devotion to maintaining spacing between vehicles (often called headways) is increasingly coming into conflict with the way transit systems have traditionally been run: with a stop-based timetable letting riders know exactly* when a bus is scheduled to leave a certain stop. In a headway system, the guiding logic is that riders don’t really care what exact time a transit vehicle leaves a stop, as long as it’s frequent enough that they won’t wait long for the next one, and that the time to their destination is reliable (Walker, 2010). Taking that into account, the payoffs of switching to a stigmergic self-organizing model could be huge, with the end result of the research team’s method being an “improvement in average journey time of approximately 20% and a decrease of 25% in mean headway values.” In a rapidly urbanizing world, transit agencies are uniquely suited to offer more sustainable and efficient transportation solutions than single-occupancy vehicles, but are also put in a position where they must offer competitive service with dwindling funding (Buehler, 2018). Automation could be an essential key to creating more competitive transit, but questions still linger as to whether riders would be willing to use a system that has the cool, unfeeling logic of a termite.

Buehler, R. (2018). Can Public Transportation Compete with Automated and Connected Cars? Journal of Public Transportation, 21(1), 2. 

Carreón G, Gershenson C, Pineda LA (2017) Improving public transportation systems with self-organization: A headway-based model and regulation of passenger alighting and boarding. PLoS ONE 12(12): e0190100. https://doi.org/10.1371/journal.pone.0190100 

Walker, Jarrett (2010, October 25). Beyond “On-Time Performance.” Human Transit. Accessed November 29, 2018, https://humantransit.org/2010/10/beyond-on-time-performance.html
-Edited by Eavan Moore

Comments

Post a Comment

Popular posts from this blog

The worst congestion in the world

-
Image
While I was going to school at UCLA, the car-culture was very apparent to me. The city also felt incredibly spread out, and it would sometimes take me more than an hour by bus to get downtown. I did not own a car the entire time I lived in LA, and I felt very limited. I quickly became bored with Westwood, the neighborhood that UCLA is in, and the only neighborhood that was within walking distance of my apartment and I had to rely on my friends to drive me to the beach or other neighborhoods. I was surprised when I read in Sorenson’s article, “Moving Los Angeles”, that despite Los Angeles reputation for sprawl, it is actually quite dense when compared to the nation’s 14 largest metropolitan areas. In class, we talked about how Los Angeles is the only major city that has become denser since the 1960s. Los Angeles is not as dense as New York City, but it is quite dense at a regional scale. The suburbs are denser on average than suburbs in other cities. Reflecting on this more, I realized...
Read more

Uh oh. Does Vision Zero Reinforce White Supremacy in the United States?

-
Many US cities, including Portland, have adopted Vision Zero strategies as a response to pedestrian and bicyclist traffic safety needs. Vision Zero, a traffic safety approach which originated in Sweden, is a program that aims to ultimately reduce the number of traffic-related-deaths to zero (Vision Zero Network 2018). The program’s approach is multifaceted, using public education, street design, legislation and law enforcement to reach its desired outcomes (Elevbakk 2007, Trujillo 2014). Sounds like a win-win, right? Ah, but let’s not forget our mantra of equity: “who gets what when and why?”. There is often more to the policy than we see at first glance. Indeed, Vision Zero does have its critics. Critiques of Vision Zero focus on concerns related to equity – including issues related to location of infrastructural improvements, and racially biased enforcement of traffic related laws (Bliss 2016). In cities like Los Angeles, Chicago, and New York, mobility justice groups have raised c...
Read more

The age of automation

-
Image
Cities across the nation, including Phoenix, Boston, and San Francisco, have already begun allowing transportation network companies (TNCs), such as Uber and Lyft, to test out new autonomous vehicle (AV) technology. However, after the March 18 Uber crash, which resulted in the death of a woman, many cities put a halt to the testing. Despite this incident, cities have not terminated their plans to introduce self-driving vehicles onto their streets. Some cities, including Boston, MA, are gradually introducing AVs, starting with small driverless zones. Philadelphia, PA, has established a rigorous testing process. AVs must meet important standards, such as emergency braking and basic driving capabilities before the vehicles are released to the streets (Krauss, 2018) . Many cities are still excited about the potential benefits of AVs. The Boston municipal government argues that the introduction of AVs could lead to improved accessibility for people living with the aging population and ...
Read more