Frequency vs. Coverage
Updated: Jul 27, 2018
A good deal of debate on transit system design rests on one question: should we design to maximize ridership, or to make sure that it reaches the entire population?
The More MARTA debate is exciting. I’d never imagined that Atlantans would be so eager for transit and interested in talking about it. As a researcher, I tend to think about the technical details involved. I've been doing a deep dive into the technical analysis for the More MARTA plan. There seems to be some interest in how the decisions about what to include in the expansion plans came to be, and I plan to write a few pieces up on it. However, before I jump into the details, it’s worth contemplating the question “what is a transit system supposed to accomplish?” This sounds simple, right? Transit systems should move people quickly and efficiently, but beyond that, we need to dig a bit deeper. For example, one of the major considerations for a transit system is whether it should optimize frequency (and with that, ridership) or coverage. In other words, should routes be designed to achieve the maximum frequency, or should it be accessible to the maximum number of people? With unlimited budgets and an apolitical world, both of those goals would be achievable. Unfortunately, budgets are limited and transportation decisions are very political. Jarrett Walker dives far deeper into this issue here: Explainer: The Transit Ridership Recipe. Historically, MARTA and most US transit agencies have leaned towards coverage networks. Take a look at some of the MARTA routes and note how long and looping they appear. This is because MARTA is trying to provide access to as many people as possible. This is a good thing, but longer bus routes mean lengthier and less frequent trips. However, some of MARTA’s recent route changes suggest that MARTA is moving slightly in the direction of higher demand routes that are more direct and hit fewer locations. This is in line with what other transit agencies are doing around the country: adjusting routes to increase ridership. So, when you think about transit systems, try to think about the purpose you think they should serve in your city. Transit agencies serve many purposes, and sometimes those objectives conflict with each other. As you fill out your More MARTA survey, or advocate for specific transit lines or investments, take a few minutes to think about what you think is the purpose of our transit system.