Tuesday, March 8, 2011

Point-specific timetables, an example

So simple, yet so complicated: Catching a bus [written 2008]

A half minute ago, laptop in hand, I boarded my bus to the local public library. It was an unamazingly commonplace activity, free of any problem or annoyance.

But it wasn't that simple, for I used a bit of self-developed technology I wish everyone had. The simple part was that I just checked the bus time on the hand-built schedule I affixed by magnet to the side of my refrigerator, and made sure I walked out the door by that time.

Point-specific timetable posted on refrigerator door

Yes, that seems simple, but consider what most transit riders face. All they have to work with is a printed bus schedule, which merely tells you when the bus passes certain points. My "value added" is to calculate the time the bus passes my stop, build in the walking time between my house and that bus stop, then back up four minutes as a buffer.

I call my creation a Point-Specific Timetable, or PST for short.

All in all, for my particular bus stop, for that bus route, going that direction, I need to subtract nine minutes from the time on the printed timetable for their timepoint nearest my house. That timepoint is only 500 feet farther away, but since it's downstream of my stop, my bus passes my stop earlier than that one, so I back up one minute. Then, as I said, subtract my four-minute walking time, and subtract another four minutes to be sure I get to the bus stop before the bus does. That's for the outbound trip that gets me to the library.

For inbound trips, I also subtract nine minutes, but the numbers leading to that amount are different. First, I need to cross the four-lane road the bus travels. This might mean waiting for the pedestrian signal, or at least for traffic to clear, so I build in a fifth walking minute. Second, since I am now downstream of that timepoint, I don't need to factor in that "upstream" minute. However, it is not enough to warrant building in a minute of travel time for the bus. Thus four minutes walking, one minute crossing, and four minutes buffer, again for a total of nine.

In this particular case, at around 9:40 I glanced at the PST on the fridge, which indicated a must-leave-by time of 10:05 for the next library trip. OK, I thought to myself, that gives me 25 minutes to pack up the overdue library books, zip up the laptop, grab my wallet (with bus pass and library card) and cell phone (which doubles as a watch), and maybe even throw a load in the washing machine, before throwing on my coat and heading out the door.

I did all that, and when I got to the stop sign at the end of my little street, about one minute into the trek, I was pleased to see that it was 10:06. I arrived at the stop at 10:08, so I must have walked a little faster than usual. Still, I was there in plenty of time. The bus came along at 10:13, just a minute early by my figuring, but since I'd built in four minutes lead time, it didn't matter.

I waited just about five minutes, a comfortably short wait. Any less, I would have worried about missing it. Much more, I would have grown impatient.

The point of it all was that I was able to use my little PST tool to plan when to leave the house in order to catch the bus, and also to give myself enough time to prepare properly for the trip. Since the tool has the must-leave-by times figured out in advance, I don't have to figure it out. Bing bing, glance at the chart and the clock, all of two seconds, and I have all the information I need to make a snap decision.

Perhaps some really experienced transit riders have built all this into an internal clock, but most people are not experienced transit riders. Even for me, it really does help to have a tool that makes transit so much easier to use.

My plan is to equip every home in America with their own PST so that everyone can use transit as easily as I do. This would help lessen our dependence on foreign oil, and also allow taxpayer subsidized transit systems to pay their own way.

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