Friday, May 28, 2010

Mode choices

Recently, I've argued that we would expect an S-shaped shift from private cars to transit if the following conditions hold:

Efficiency: for every dollar of subsidies, transit gives people more access to places where they want to go than cars do.
Demand: people patronize systems depending on the access that they offer.
Representation: subsidies are distributed based on demand.

I've now discussed efficiency and representation. I've touched on demand before, but it's the kind of thing you can say a lot about: what factors go into a person's mode choice? Recently, EngineerScotty and Jarrett Walker have also discussed some of the motives for mode choice. But before I do that, I think it's important to observe that "mode choice" actually covers several different choices that people can make.

You might think that a mode choice was a universal, permanent decision, such as "I will walk everywhere I go," or "I will always take transit." But that actually doesn't happen, unless someone's really trying to make a point. Even the most diehard walker will probably take a ferry if there's no bridge available.

At the opposite end of the spectrum, but pointing in a similar direction, no transportation system provides door-to-door service for every possible trip. It may not matter for our goals that someone walked the thirty feet from their front door to the car, but it may matter that once they got out of the car, they walked a full city block length to get out of the parking lot.

One kind of mode choice is per trip, based on particular circumstances ("It's icy, so I'll leave the bike at home") or as a trial. Often, it's based on whether the vehicle will be an asset or a burden later: someone may drive because they're planning to go straight to their country house after work, or alternatively they'll take transit because they're planning to go out drinking after work. In some circumstances you can even decide on the fly for a particular leg of the trip ("I didn't see a bus, so I hailed a taxi").

If someone makes a long-term mode decision, they often don't make it overall, but for a specific class of trips. One common scenario is the suburban resident who gets to work by bus-walk or walk-train-walk, but drives to the supermarket and the movie theater. Some people have fantastically complex arrangements that they can maintain for years: subway to work, commuter rail to visit the Stamford office, car service home from work, taxi to go to the doctor across town, car to go to Vermont for the weekend, bus to get to the museum, subway to meet a friend in Greenwich Village, walk to the deli, rollerblade to the park, fly to Punta Cana.

There are also long-term commitments and investments, the most obvious one being buying a car, a bicycle, a car-sharing or bike-sharing membership, or a transit pass. Other choices include the location of your residence, how much off-street parking it has, your workplace, whether you have to travel for work and how much and where, your favorite social hangout, your shopping, your child's school, a weekend or summer house, place of worship, and restaurants. Any of these locations may be better or worse for transit, driving, walking, bicycling or skating. They will all affect long and short-term mode choices.

One of the most frustrating things for me during the congestion pricing debate was to read comments like, "It's not a choice! I need a car! I need to drive! I need a free parking permit! How else am I supposed to get from my home in Rockland to my kid's school in Manhattan and my job in Brooklyn?" What was even worse was when instead of "I" they said, "some people, unlike you elitists..."

Since our proximate goal is to get people to stop using cars, we care about all these decisions: the short term and the long term, and the commitments that influence them. The good news is that there are tons of ways that the environment can be changed to encourage people to choose transit, walking or cycling more often. The bad news is that these can be changed in the other direction too.


nathan_h said...

"One of the most frustrating things for me during the congestion pricing debate..."

It is a perpetually frustrating argument. We can't tax gas without ruining the economy, we can't say no to any new abrogation of civil liberty without being blown up by terrorists, we can't have safer ambulance driving without everyone dying on the way to the hospital. The absolutist's false dilemma is a great enemy of moral argument.

Cap'n Transit said...

Here is a comment from Jarrett Walker, via email:

I'd be curious how common the "fantastically complex arrangements" are outside of NYC. People who live in major cities get used to having lots of options and learn that none of them is right for everything. But our challenge is that mass of America that is so car-oriented that people get in the car for everything. Even when they begin to be presented with choices, they're likely to resist thinking about it, because thinking about it is a new kind of work they've never had to do. That's just my speculation. It would be interesting to see the extent of "lived multimodalism" plotted by zipcode.

Cap'n Transit said...

I think you're probably right, Jarrett, but I definitely saw a lot of this in Paris, and some in Chicago as well. I'm sure there's even more in Paris now that they have Velib' and the tramways.

I would argue there's a lot more multimodalism in the hinterland than you think. At the very basic level, everyone who's mobile at all spends some time either walking or in a wheelchair. There are a range of borderline trips where people have to make the choice of whether to drive or walk/roll. We all have some comical stories about the Californians who drove from one end of the mall to the other, but they probably didn't drive from the mall entrance to the entrance of the Dick's Sporting Goods 100 feet away. The point is that anywhere you go, people are making these choices.

The segment of the population that uses three modes (driving, transit, walking or cycling) is probably a minority, but not insignificant. In the biggest cities, it's probably a majority. I honestly don't know anyone who uses all the modes I described, but I know plenty of people in New York who use four or five.

BruceMcF said...

One of the things that keeps people "learning" that cars are a basic necessity in the suburbs is sprawl itself in particular, as opposed to just lower average density in general.

The more common each and every transport task is a distinct trip, because each task is allocated to its own development zone, the more common it is to be in the situation of, "well, I had to take a car to A, because I am also going to B, and even though there is a bus to A, it doesn't go to B".

And the more common is it for "A" and "B" to be located in easy walking distances, the more likely it becomes to develop a destination specific way of getting to that location.

Since I don't drive, I'll contrast cycling to work, cycling to the supermarket, and cycling to town. Work is at the edge of town, with a Sheetz at the front of its industrial park which I go to at lunch only because its there. I would never ride 20 mins to get a cheap Sheetz sub and ride 20 mins back home.

The supermarket is over at the eastern edge of town, where the state route that is main street and the state route that swings around town intersect again. I cycle to the supermarket and back.

In town, I drop a Netflix off at the Post Office, stop by the bank for the ATM machine, maybe stop at CVS or Walgreens to pick up some milk, or the pastry shop in town for some baklava, perhaps grab some fast food to go at toxic taco.

All up, while the cycle to town is shorter than the cycle to work, its about the same as the cycle to the supermarket. And yet, while the stuff I can get done at each of the different places in town I might stop by is much less than what I can get done at the supermarket, the threshold to hop on the bike to do something in town is much less ... partly because I might decide to do something on the spur of the moment once I'm there.

That's just me and I am extremely far from the median traveler on the public right of way out here in outer suburbia, but investing in a bike or a bus pass that only gets you to a few places is a lot lower hurdle if there is a variety of things to do at that place.

George K said...

I like your anaolgy of the long-term mode decision.
The long-term mode decison is also related to the per trip decison. Since transit tends to have higher headways on the weekends, that suburbanite that you mentioned probably made the decision to drive to the movie theater based on the fact that transit service is limited on the weekend.
It is also based on convenience. For example, when my family goes to the supermarket, we drive, since we tend to come home with a lot of food and it is too inconvenient to walk or take public transportation carrying bags from the supermarket.
Per trip is also based on what modes of transportation are available and cheaper during a certain time. For example, I receive a Student MetroCard that is valid on weekdays. At the same time, my parents are using the car to go to work. Therefore, I make the choice to use public transportation during the week for the majority of my trips, as it is free and I do not have access to a car. However, on the weekends, when my Student MetroCard doesn't work and my parents are home, we generally use the car for local trips, as it is cheaper and more convenient than public transportation.

Cap'n Transit said...

when my family goes to the supermarket, we drive, since we tend to come home with a lot of food and it is too inconvenient to walk or take public transportation carrying bags from the supermarket
Yes, but buying a lot of food is a long-term commitment and investments. We've made the choice to buy small loads of groceries, which allows us to walk around the corner to shop. We do it more often, but it doesn't take long and the food is always fresh!

George K said...

I guess the decision to have a large family could be considered a long term decision. The fact that my family is large leads to the fact that a car is more of a necessity than a 1-person household, and leads to our decision to buy large quantities of food at the supermarket. (And we don't have to worry about freshness, as we can go through large packages of food in less than a week!)

Alon Levy said...

George, it all depends on how far the supermarket is. My family has generally walked to the supermarket: it was close, the streets were walkable, and no matter what happened, carrying the groceries from the garage to the apartment would be as big of an effort as carrying them from the supermarket to the entrance to our building. In one city, the supermarket also had free delivery services for large purchases, which we made liberal use of.

George K said...

Part of it was that once we got used to the convenience of owning a car, we didn't want to give it up. As a result of having jobs that were difficult to reach by public transportation, a car became more necessary. That, plus the fact that a result of having a large family, there were more places that we need to get to, led to the decision to get a car.
My family does live close to a supermarket, and on the way back from school, I often pick up odds and ends at one of three supermarkets I pass on my way home from school. However, due to the fact that we have a car, we drive to the supermarkets that we prefer instead of walking to the closest one. This is one example of us doing something ''because we can''. If the job was closer, we wouldn't have a car, and would therefore do more shopping at the local supermarket, or make more trips to the supermarkets that we like so we can carry the food home.

Cap'n Transit said...

Yes, and if you (and your neighbors with cars) shopped at the closest supermarket more often, they would probably carry more of the things you wanted.

George, I suggest you read my two earlier posts on the supposed convenience of cars and the supposed independence of cars.

George K said...

As a local supermarket, it is fairly well used. However, the reason that I don't shop there is not because of the lack of selection. It is because the staff at the other supermarkets are much more respectful, easygoing, and helpful, and the prices are lower at the other supermarkets.
That being said, even if I didn't have access to an automobile, I still have my free Student MetroCard, and even if that were taken away, the next closest supermarkets are only a mile or a mile and a half further, easily walkable at my young age.
I read the 2 articles, and although I see the disadvantages of a car, I am still in no position to tell my parents whether or not it is necessary to have a car. In my opinion, we would still be able to manage with or without a car. Having 1 car and 6 people, we are much less auto-dependant than most Staten Islanders, where the average car:person ratio is 1:2, compared to our 1:6 ratio.

Jase said...

Ahoy, cap'n.

I have dwelled extensively on the interaction between the long-term and short-term decision and wondered what makes people buy their first car.

I observe that people are likely to buy that car for some unusual kind of trip. (Or at least, that's what they say.)

I've tried to make a model to explain this:

There are trips (such as getting to work) where any individual mode will have very elastic demand in the long run. Because we do it every day, we can plan a public transport option.

We might know the timetable backwards, buy a house near a station, or invest in a yearly ticket.

Then there are trips that may be of 'lower' personal value, but the demand for the car mode will be very inelastic. These are 'unusual' trips that were harder to plan for.

For example, I play soccer every weekend in a different location. Or I may experience a need to go across town at night for volunteering. Or I may have classes that run late.

In each of these cases my trip _could_ be served, more or less, by public transport. But because these are once-offs, at after-work times, the car is a 'better' option.

If these activities persisted, the car might not be bought. But their impermanence makes the planning costs of PT high.

The other feature of 'low elasticity' non-repetitive trips is that at those times, while we may be keen to get home for dinner, the PT system is likely to be at its least frequent.

And so, people will buy a car for a small unusual trip.

There is then a cost to getting rid of a car that means people will retain a car and use it for more and more trips.

The policy conclusion that I draw is that PT planning should work to fight for trip choice ('car or bus today?') but also should fight for long term mode choice ('should i buy a car?')

This might mean running more buses at non-peak times, running cross-town buses empty, linking metro and intercity transport, etc.