Trip Chaining

Gendered Innovations’ charts of trip chaining and gender breakdown of public transit riders got me thinking about how different systems of transportation handle a mixture of short and long trips. Eric Jaffe at The Atlantic Cities reports this and suggests that transit agencies orient physical features such as accessibility to the needs of women who trip-chain care and work trips.

But to me, the first observation is that although women trip-chain more, it doesn’t seem to be true that women are more likely to ride transit in the US than men just because of trip-chaining features. Instead, women traditionally have been less likely to have jobs requiring commuting, and the commute gap has been shrinking more slowly than the gap in employment.

This comes from the fact that trip chaining on transit is cumbersome in most cases. Both cars and transit have to deal with the time it takes to stop for an errand, but transit tends to handle this worse, unless it’s very frequent and has practically zero access and egress times. Transit cities instead get people to take their short errand trips on foot – since their neighborhoods are denser and have more mixtures of uses, they make retail and care trips attractive on foot. In light of the fact that walking is not useful for long commute trips and transit is not useful for short errands, we can construct the following typology of cities:

Long \ Short mode Foot, bicycle Car
Transit Transit-oriented Traditional suburban
Car New urbanist, small-town, auto-oriented dense Auto-oriented

Auto-oriented cities are the easiest: in those places, people drive for all purposes. Trip chaining can be done on a commercial arterial road, dropping off laundry or kids or buying something on the way to work, and because of ample parking availability, the time each additional link in the chain consumes is very small, since the longest access and egress time comes from navigating from the residential cul-de-sac to the arterial and from the arterial to the office park.

Traditional suburbs, common around New York and Chicago and sometimes in other old North American cities, are similar for trip-chaining purposes. In those areas, the urban form is suburban and auto-oriented, but work trips to the city are done by commuter rail or occasionally commuter bus, since the city is not as auto-friendly as the suburbs.

Transit cities too have their long-range commuter rail, but it is built as an extension of walking rather than of driving. Neighborhoods tend to have mixed uses, and there’s a concentration of retail development near the outlying stations, sometimes forming large secondary clusters but sometimes just acting as neighborhood centers. It could take considerable time to add more trips to one chain, especially if not everything is located at the train station. But conversely, the amount of time a single short trip takes is small, unlike the case for auto-oriented cities – the supermarket is right around the corner, and within five minutes’ walk are plenty of stores. When people walk, the concept of a single trip begins to lose meaning then. Potentially, every single purchase can be considered a separate trip, in which case the chaining becomes quite long.

In many places the transit is absent and people drive outside the neighborhood, while still doing errand trips on foot. This is the typology that characterizes different environments including new urbanism, traditional cities like Providence and Tel Aviv that have been made car-oriented, and auto-oriented modernist projects such as Co-op City. Those environments all differ in how trip chaining is done. In principle, it can be done on foot, but usually people who can drive do.

If my own experience is any indication, one feature of cities in this typology is that children and teenagers walk more. In Tel Aviv, my father drove me to elementary school on the way to work while (in later grades) I walked back, and I took the bus to and from middle school. Most trips my parents did in a car, but there was a reasonable number that were short enough to walk. I’d walk to farther destinations such as the cinema and the urban mall. The view of the North Tel Aviv middle and upper-middle class of the 1990s as I remember it is that the bus is fine for trips to school, but adults drive. I doubt I’d have had the same view if I’d grown up in New York, or for that matter in the Houston suburbs, where everyone drives or is driven.

Although most of the discussion about transit cities contrasts them with car-oriented cities, the other two typologies need to be examined, too. When adults and children trip-chain differently, children can get a distorted view of who transit is for (poor people, people who can’t drive yet), and the next generation will make the city auto-oriented; this is indeed what is happening in Tel Aviv, which despite population growth in the core is adding cars and spawning low-density suburbanization well outside the built-up urban areas.

Likewise, Cap’n Transit’s attacks on park-and-rides don’t quite capture what is wrong with the car/transit typology. A transit agency that wants to make it easier to trip-chain will want to concentrate development near the train stations, because that’s where it’s easiest to add minor trips without having to walk ten minutes out of one’s way. Of course in the middle of the dense city there’s development everywhere, which may well be orthogonal to where the subway is, but then trip-chaining becomes easier because each foot trip is so short.

The principle is that cars are a big one-time purchase but have a much lower marginal cost of usage. If one major class of trips can’t be done on transit – and chained trips generally can’t when they require the rider to wait for the next bus and the next bus will come in 15 minutes – then people will buy a car and then drive it even for trips they’d happily take transit to if they didn’t already own a car. The class of trips that can only be done conveniently by car needs to be kept small enough that people will use car share, take a taxi, or beg a friend who does own a car.

Thus what transit agencies and pro-transit politicians should devote more time to is appropriate development more than physical features of the transit system. Accessibility is important for so many reasons other than strollers. In contrast, the primary importance of using transit to extend the range of the pedestrian rather than provide a capacity boost for the car is precisely that transit needs minor trips to be doable on foot. A transit system that one needs to take to the supermarket may be technically successful, but it’s in a failed urban area.

16 comments

  1. Shlomo

    Like Manhattan, Tel Aviv will never become fully car oriented. Land is too valuable, the resulting development too dense (population-wise, most of the new upper-middle-class development in Israel is in “luxury” apartment towers, not low-density suburbs), and cars will always be too inconvenient (except perhaps if they someday become self-driving).

    • Alon Levy

      Not fully, but more than today, and more than in New York, Paris, and other transit cities. Even today, the Central Bureau of Statistics reports that there are 400 vehicles per 1,000 residents registered in Tel Aviv. In New York, the number is 250, and in Manhattan it’s 150. For a city that’s more comparable to Tel Aviv, consider Kuala Lumpur – designed around the same garden city principles, and also choked with roads and cars.

      The other issue is that cars are still aspirational in Israel, and they aren’t in the US or Europe. Last time I visited, I saw ad posters on the Sherut vans, “Today, you’re in a taxi – tomorrow you’re in a car.” You won’t see these in New York. You won’t even see them in Providence or New Haven, two cities where a fair amount of the population doesn’t own a car, out of poverty.

      • Adirondacker12800

        Keep scale in mind. You could move the entire population of Isreal to New York City and have room left over for potato farms in Staten Island. ( Gawd I’m getting old. A&P sourced produce locally if they could. Staten Island potatoes in October, November and December…I know what an A&P is… it was across the street from Woolworth’s.. ) Or you could move the entire population of Israel to New Jersey with room leftover. The reason the Bronx needs the IRT is that Manhattan is on the other end.

        “Today you are in a taxi, tomorrow you are in a car” doesn’t work in North America. Outside of metro New York people don’t use taxis. In metro New York people don’t want cars if they are someplace where they can hail a cab.

        • Alon Levy

          To explain the context a little better, Tel Aviv has popular vanshares running the routes of the busiest bus lines, which are called sherut (service) taxis. They’re a bit more expensive and a bit faster than the regular buses. In context, the ad meant, “Today you use vanshare, tomorrow you are in a car.”

          That Israel is small is neither here or there. It has almost the same population as Switzerland, and more than twice the population density.

  2. anonymouse

    Transit doesn’t have to be bad at trip chaining. In particular, it can be very convenient to have stores next to a transfer point, so that transferring riders can go do something useful while they wait, in which case they get trip chaining basically free (or included in the time cost of the transfer). Transfers are much less annoying when you have something to do other than stand there and watch cars drive by while you’re waiting for your bus.

    • David Edmondson

      It really depends on the type of transfer point and the type of shopping. A well-coordinated transfer point will leave very little wait time for passengers, and if it’s in a suburban context the next bus might be in an hour, turning that 20-minute jaunt across the street into a 60-minute wait.

      • anonymouse

        Ideally, a transfer from a more frequent but less predictable line to a less frequent but more predictable line: you’re likely to get a bit of spare time once in a while if you want to avoid missing your connection, or if you’ve just done so. And ideally, it’d be the kind of side-trip that can be done fairly quickly, maybe 10-20 minutes at most. For example, grabbing a donut on the way to somewhere else.

        • David Edmondson

          My experience has been with Golden Gate Transit, the bus system in the SF suburb of Marin, which often feels like there’s no time to refill the transit card, let alone grab a donut. At least, that’s when it works right. But I suspect this kind of precise coordination is unusual.

          Those side trips, though, can be facilitated with real-time arrival information in the donut shop, on the smart phone, at the bus stop. If I knew my bus wasn’t arriving for 5 minutes, I could budget that time for coffee or a donut; if I thought it was coming at 10:30ish, I’d want that five minutes as buffer.

          • Alon Levy

            For what it’s worth, at Kennedy Plaza the only retail is of the donut shop, 7-11, and Subway variety. One way that good urban design could help is that it could make the area less sketchy; Kennedy Plaza had and to some extent still has bad reputation, and this discourages retailers from locating there, making this kind of trip chaining less useful. Another problem is that the city built a mall half a kilometer away, separated by a wide, pedestrian-hostile arterial road; it would’ve worked much better if the mall had been truly walkable from both the train station and Kennedy Plaza, but instead the city made walking from each one to the other two a chore.

  3. Nathanael

    “New urbanist, small-town, auto-oriented dense”
    By your typology, this is where Ithaca is. Long trips are all by car; short trips are done on foot or bicycle. It seems to be getting only more so. I wonder what’s going to happen, since it’s growing. It seems to be veering sharply away from the “auto-dominated” model, but there’s still very little in the way of transit; can auto-oriented dense survive high population growth?

    • Alon Levy

      I wasn’t thinking of Ithaca, but you’re right, it’s another good example from what little I know about it.

      As for population growth, every mode has its limits. That’s why in growing cities you’ll often see the fastest growth on the margin, be it the Bronx and Queens in 1900-30 or the suburbs in the postwar era. Clearly transit-oriented cities can hold more people than auto-oriented ones and commuter suburbs, but I honestly don’t know about auto-oriented dense. For what it’s worth, Tel Aviv is quite dense despite being completely car-oriented for long trips – even some of its auto-centric modernist sections, such as Ramat Aviv, are pretty dense by most Western cities’ standards. That said, it still retains a lot of transit use in its core areas, though it seems to be moving away from that, and grows a lot slower than its suburbs.

    • Adirondacker12800

      The fastest growth is on the margins because that’s where the unoccupied land is.

      • Nathanael

        Growth on the margins is happening a lot less in Ithaca because of agricultural land preservation. One of the main industries is boutique agriculture, and people care about that.

        Also, driving into a city which is a dense undriveable location isn’t any fun, so at this point the trends towards living downtown are feeding on themselves (among the non-farmers, anyway).

        I genuinely wonder what’s gonna happen. There was a “Keep Ithaca Small” movement but it kind of died out, so I suspect it’ll keep growing (unless fracking destroys the area).

        There’s been some tendency for population growth to jump directly over the farmland to the next neighboring towns, creating choked roads during commuter hour along the routes from Cortland or Candor or Elmira. The next logical step after that is intercity public transit for these commuters who “jumped the greenbelt” in London terms — but nobody seems to be thinking about building any such thing, and it’s being defunded where it exists.

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