As someone who does not drive, should not be trusted to drive, and is not legally allowed to drive, I spend a fair bit of time on public transit. It’s not as much as other people I know—working from home within walking distance of most of my groceries is pretty great—but it’s enough to develop a lot of feelings about the ways that public transit can fail. Much ink has been spilled about things like making sure a system’s vehicles arrive at consistent times, go places where people want to go, are frequent enough to make looking at a schedule optional, and so on, and today, I want to focus on an underrated aspect of making a transit system upon which a person can truly rely: edge cases.

Many transit systems, especially in places whose overall design is overtly car-centric, focus on adding transit options to heavily utilized routes, typically those used during morning and evening rush hours. When transit systems struggle for funding against police departments that get blank checks from the municipal budget and highway networks that are treated as critical infrastructure in ways that transit systems rarely are, this makes sense. Heavily utilized commuter routes can build ridership to high levels quickly and can become the backbones of a transit network, so it makes sense to build them first. In the twisted logic of car-centric urban planning, these routes are among the few that have what it takes to justify their existence. Anywhere else in town will often be completely neglected by transit planners, deemed uneconomical to serve. If less-used routes are allowed to exist—perhaps the system is mature enough that even often anti-transit planners deem it worth the investment—they often have barely-adequate stop infrastructure (often just a sign with route numbers), low frequency, inconsistent arrival times within that low frequency, and limited hours of operation. How difficult a place is to get to by public transit varies wildly from one destination and trip timing to another, and often, it’s flat-out impossible.

Compare this to how roads networks in developed countries work. Drivers can count on paved surfaces on which their vehicles can operate between virtually any two points in their city and most of the paths between cities. Only the farthest-flung, poorest, or most natural places will have roads that aren’t paved, let alone be completely disconnected from the road network, and most of these will be gravel roads that are good enough for low speeds. Whether a driver’s starting point is an industrial park on the edge of town, a remote exurb separated from its city by a stretch of greenbelt, a path running through a park, an urban nightclub, a cottage deliberately disconnected from nearby towns, or a university neighborhood, that driver can count on uninterrupted, accessible road surface from one end of their trip to the other, usable at any hour of any day, including weekends, holidays, the middle of the night, and when they’ve had too much to drink but will go ahead and drive anyway because how else are they getting their vehicle home tonight? Drivers rarely must answer the question “how am I getting there?” or “how am I getting home?”—their status as a driver is the answer, because the road network doesn’t care if your route is “heavily utilized” or “profitable.” It is treated as the public utility it is and is heavily subsidized to make sure even remote places in and around cities are connected. A road might be poorly maintained to the point of damaging cars that use it, but in the 21^st century, it will rarely just not exist at all and it will almost never care about what day or time it is being used.

This is an unthinkable level of freedom to a transit user. Transit users must constantly compute whether they have enough time to get to the bus stop with enough cushion for an early bus arrival on pain of being late or worse, stranded. They must choose which outings they attend and people they visit based on what places have bus service when. They must time their departure from evening outings to make sure it’s before the last bus that gets them home. They must choose flight times at their nearest airport based on how early the bus system can get them there and whatever unthinkably huge time cushion the local security theater demands of air travelers. They must be extra careful about visiting friends who live in residential neighborhoods (you know, where most people live) because past a certain time of night, a visit to a residential neighborhood becomes an overnight stay.

And looming behind all these calculations is a perverse reality: I could ask for a ride.

The backstop behind every gap in transit coverage is the humble passenger seat. Whether paid for or provided as a favor, passage in someone else’s car opens all the paths that the transit network left closed and makes trips possible that the transit system decided not to. And it is a stark reminder to every single person who ever makes use of this backstop that they, too, could have this freedom, if they had a car and a license.

It is these cases that truly make the difference between a transit system that solves specific problems and one that a person can build their life around. If it is possible to arrive by public transit in time for all the security theater that precedes a 5 AM international flight, or return from a visit to a suburban friend that runs late into the night without sleeping over or importuning them for a ride, or visit a far-flung industrial park for an event without the path home involving a 20-minute pitch-dark no-sidewalk lope to the nearest transit corridor, then a person can truly rely on the transit network to facilitate the fullness of their life. A public transit network attains its true potential when the freedom of public transit users approaches what automobile users experience just from the fact that roads can be used whenever. A public transit network attains its most complete victory when the only people who need cab drivers are people who, for whatever reason, refuse to engage with public transit, not people public transit is failing to deliver to their destinations in a timely manner.

I should never have to take a cab to the airport or ask friends for a ride home.

It is the edges that build the center, not the other way around.