Photo by London Permaculture on Flickr.

A Metro rider, Barbara, wrote in to Unsuck DC Metro about a problem where she added funds to SmarTrip online but then still couldn’t go through a faregate. What’s going on is one of the unfortunate consequences of the 1990s-era faregate systems WMATA is still using.

I had added funds online on March 4. I didn’t use my card before March 18, and when I did, I had to realize that there was still only 20 cents on my card, and the $50 I had added at the beginning of the month were nowhere to be seen. …

I couldn’t use them for riding because the funds wouldn’t load, and I couldn’t even go through the turnstile with them. So, what I did was use my credit card to add $20 to my card (I didn’t have any cash on me), entered Foggy Bottom, exited at Ballston and: voilà! there were $68 on my card all of a sudden.

This is obviously frustrating to infrequent riders who load up funds ahead of time for when they ride, or use automatic loading to ensure their card is never low on funds. But the automatic or remote loading may not work.

This happens because of the way the (fairly outdated) SmarTrip system works. When you add funds to your SmarTrip card online or automatically, the funds don’t appear in your Smartrip account immediately because your balance is actually stored encrypted on the card rather than on a computer.

Adding funds online sends an instruction to the SmarTrip system to watch for your card. The next time a faregate or bus farebox reads your card, it will have information about what you added, and will load the funds onto your card.

The load instructions get copied to faregates and bus fareboxes throughout the system, but because these machines are not in constant communication (like bus fareboxes), it may take several days for the instructions to reach a farebox you use.

But Barbara waited more than a few days. What happened? She wrote:

I called SmarTrip, and they didn’t have a plausible explanation: All I learned was that this could happen “with infrequent use of the card.” What the heck does that mean? It shouldn’t matter how frequently I use the card — it’s my money on there, it’s just not in my bank any longer, it’s on their card!

Here’s what’s going on. The faregates have their list of SmarTrip cards that are waiting for new funds already loaded online. Unfortunately, the outdated faregates have limited computer memory (that fact restricted peak-of-the-peak, for example). They can only store so many load instructions.

Spokesperson Dan Stessel said:

Each target [the SmarTrip computer system in the faregates] can hold a maximum of 85,000 auto loads. When that number is exceeded, the system has to localize, meaning the system will send your auto load purchase to every station you’ve used in the past month.

Furthermore, based on the SmarTrip customer service response, it sounds like if you load online but then don’t use the system soon after, newer load instructions may crowd yours out.

Either the Ballston gate had the instruction and Foggy Bottom did not. (Barbara said that she lives in Arlington, so Ballston is probably the station she uses most.) Alternately, once Barbara loaded her card at a machine and then entered the rail system, the central system retransmitted her load instruction to the faregates. Then when she exited, the gate at Ballston knew to add her funds.

This whole mechanism of getting the load instruction onto the faregates ahead of time is fairly messy. It would be better if, when you went onto the system, the faregate could just check your balance with a central server, but the faregates don’t have a high-speed, always-on connection to a central server to accomplish this.

WMATA is studying new fare payment systems. Any new system ought to fix this irritating problem, but it may be quite some time before a new system actually comes on line.

Meanwhile, it might make sense for more infrequent riders to use the vending machines, especially if they let their cards get very low.

Michael Perkins blogs about Metro operations and fares, performance parking, and any other government and economics information he finds on the Web. He lives with his wife and two children in Arlington, Virginia.