Most of us have been there: We need to get around the city for the day, so we load some money onto our TAP card for our bus or train fare. We don't know how many transit trips we're going to take for the day, so we play it conservative and buy a fare or two, saving a few dollars off the all-day pass. Come the end of the day, we've taken half a dozen transit trips and spent twice as much as if we'd just bought the day pass in the first place.

Or maybe you're more familiar with the reverse: You expect to use transit quite a bit over the next week, so rather than pay a few bucks for each ride you decide to spring for a weekly pass at a cost of $25. Things come up, plans change, and suddenly you realize you've spent 25 bucks for 7 dollars worth of bus rides. It's the gym membership of transportation spending.

In most cities, LA included, we're expected to make a prediction about how we'll use transit for the next day, week, or month (or even year), and make our fare purchase based on that prediction. If we overestimate our transit usage, we overpay; if we underestimate our transit usage, we overpay.

For infrequent transit users these situations are bearable, though inconvenient and frustrating. The worry that you might make the wrong choice is an annoyance, but little more. If you're a low income worker, a student, or an elderly resident on a fixed income, however—someone who can't afford even minor financial mistakes, or who doesn't always have the cash flow to put up $100 at the same time each month for a 30-day transit pass—this is a serious problem.

It doesn't have to be this way, and it's time the LA Metro and other regional and municipal transit agencies adopt a more equitable, fault-tolerant payment structure. For an example of what it should look like, we can look to Christchurch, New Zealand. (Hat tip to Darren Davis for the example.)

Pay-per-trip, with daily, weekly, and monthly caps

In Christchurch, there are daily and weekly spending caps that eliminate the possibility of overpaying for transit service. This has allowed them to do away with daily and weekly passes entirely.

Instead of purchasing daily or weekly passes, you simply use your fare card as an e-wallet and pay for each trip directly. When you reach the spending cap for the day, any additional trips you take that day are free, exactly as if you'd purchased a day pass—but without the requirement that you pay for all your rides up front. The weekly caps work in exactly the same way.

Per the table below, Christchurch's daily cap is set at $5, and the weekly cap is $25.