A frequent commenter on HT asks this in an email (the links are mine, not his):
On Second Avenue Sagas, one of the discussions went on a tangent that left me wondering about transfer penalties. If you need to walk from one station to another on the street to transfer, do the ridership models assign a higher penalty than if there's an enclosed corridor between the stations? In addition, for systems that have faregates, is there an extra penalty for transfers that require exiting and reentering?
Modeling can be a murky business, and I'm definitely not a modeler. But the bottom line is that the factors used in a ridership model have to be based on some sort of reality, and the reality of North America and Australasia is that most connections are not especially pleasant or easy, especially when there are fare penalities or delay-inducing features such as fare gates. Ease of connection varies a lot from one situation to another based on factors that are hard to model -- not just walking distances but things like street crossings, vertical circulation systems (stairs or escalator? elevator?), and of course fare co-ordination. Improvements in other areas can make a big difference. Smartcards, for example, are faster and easier to use than magnetic strip tickets, which must be manually inserted in a slot; these should make connecting easier.
So my guess is that it's hard to model transfer penalities very exactly. But let me pass on the question to all the anonymous modeling professionals that are reading. What's your answer to this reader's question? If you're working in North America, do your transfer penalties consider very high-quality transfers, such as the cross-platform connections that often occur in European subways? BART in the San Francisco Bay Area may know something about this, since they do have a cross-platform connection in Oakland, though it's only used for low-demand trip pairs and so may not offer sufficient robust information. Agencies that do a lot of timed-transfer among buses, especially at island stations where no street crossings are required, may also know something about this.
Modelers! If you're not comfortable posting a comment here, send me an email, and I'll use it anonymously.