Bus reliability and Planning TIme

If you ask people what they want from public transport, they usually say "Speed." But if you look at behavioral data, speed isn't the most important factor. Reliability is. I would rather take a bus that takes 40 minutes guaranteed, than a car that takes 20 minutes but might take 60 if there is traffic. Uncertainty is stressful. Knowing "I will arrive at 8:55 AM" is worth more than "I might arrive at 8:30 AM". This is why dedicated lanes (BRT/Tram) are so powerful. They might not be fast, but they are predictable. We don't need to break the sound barrier. We just need to keep a promise. Do you prefer a fast gamble or a slow guarantee? - Juan Mora Triana

When my bus was scheduled to arrive at 7:55, I had to catch the bus scheduled to arrive at 7:40, because the second bus was late in picking me up. I worked in an office, being 5m late wasn't critical--but it earned me an unfriendly glance from my boss. And so, I started taking the earlier bus. And so, what was nominally a 23m trip (7m walk, 13m bus ride, 3m walk) started to eat 40 minutes out of my day. 

Making it worse was the irregularity in what was nominally a 15m bus. The 7:40 bus would be on-time, or early. The 7:55 bus would be 7-10 minutes late, reliably. So reliably that I began to time my walk from my house to the bus stop to start when the 7:55 bus was supposed to arrive, knowing that the bus wouldn't have arrived before I reached the bus stop. But that was for a bus I took five days a week. 

When I was trying to take a new bus to someplace new, I'd stroll up to the stop, pull its schedule out of my pack of pamphlets, use the system map to check which routes it serviced, pull out the appropriate schedule for the route, and check my watch. Then I'd take half the headway and estimate the blocks, figuring I could make 8 SLC blocks (~1 mile) in 20m, and that the bus moved about 3x that fast. For a 15m bus, I'd estimate a 10m wait (half the headway plus some uncertainty). For a 30m bus, I'd estimate I'd be waiting 20 minutes--the actual wait time plus what I could have walked waiting for the bus. For the hourly bus--I'd start walking. The combination of wait time plus uncertainty plus lost walking time made it a bad bet--my standard estimate was that I was better off walking two miles than waiting for an hourly bus. 

Even today, any trip under 10m, I walk. It's less stressful, because it's less uncertain. Even with a bus with a 15m headway, odds are I'll make it a half mile before the bus comes. I've repeatedly had the frustrating experience of seeing the bus I would have liked to take pass me by... but not often. 

Rapid transit, it's the same calculation, except that I remove the mental 'penalty' for potential to be late. The station will be nicer, there will be places to sit, there is an arrival time count-down [2] and I know the vehicle will be on time. Riding TRAX in SLC, if the train was 15m late, I'd tell me wife "Someone is probably dead" [1]. 

This also tied into my willingness to make transfers. My rules of thumb were that it was always worth it to transfer between a 15m bus and rapid transit, sometimes worthwhile to transfer between two 15m buses, and worthwhile to take a 30m bus TO rapid transit (but not the reverse). Anything else, I was better off walking. So I did a lot of things like taking TRAX west then south and then walking east from a Trax station, because it was a better bet than just waiting for a 30m bus to take me directly south. The bus would either be delayed in arriving or delayed enroute, where TRAX was practically a guarantee.

Admittedly, I was young and fit, with plenty of time to kill, and Salt Lake is a very safe city. But I also didn't have any other options: No car and lack of plowed sidewalks/lanes made biking in winter in SLC prohibitive. 

[1] After enough highly reported crashes at railroad gates, people quit racing the train, but someone racing the train at a red light stills seems like an annual event. SUV drivers are used to being the biggest thing on the road, but in a car-eat-car world, a train is an apex predator.

[2] Transit Information systems that only provide scheduled GTFS arrival times, rather than real-time GTFS data about vehicle location are a cruel joke, so knowable false that they can only be considered a deliberate deception.

Waiting For Transit

"Service frequency determines the average wait time for transit, and thus much of the overall travel time for a trip"

Q: Reallly? People spend that much time waiting for transit? 

A: Not average trip time, average wait time. Wait time, however, is a substantial portion of many transit trips, and the part of the trip people hate worst. The lit says that riders treat a minute of wait as the same as multiple minutes of in vehicle time. Many UTA buses (especially in Utah County) run at 20, 30 or 60 minute headways. Once you include the amount of time you have to wait when the bus is late, this can mean substantial waits. Given that people choose transit based largely on its time competitiveness to the automobile, this is a significant issue. It's most significant for short trips.  TRAX is frequent and (generally) reliable,. A 10 mile bus journey on a local bus is pretty miserable. WFRC likes to use 5-10 minutes for the wait, but I don't that that effectively reflects how miserable the experience is. It assumes people know where the bus stop is, how long it will take to walk there, and how long the wait will be. That is valid if you are taking the bus to work, once per day, but doesn't reflect the experience of using the bus for general transportation. The longer the headway, the higher the time-cost of missing a bus, so the more likely you are to leave your current location early to make sure your make it. If you have to use an (unreliable) bus connection to make that connection (such as bus to FrontRunner), there is even more waiting, because you can't control if you arrive 10 minutes early or 2 minutes too late, so you have to be 25 minutes early to be guaranteed a connection. Hence, I prefer to assume random arrival, at 1/2 headway, for any bus. This becomes increasingly important as UTA moves away from the '1-seat ride' model and toward the more efficient 'transfer network'. 

Consistency Matters

I have friends who would never willingly ride a bus who will eagerly take a ride on TRAX. I cannot blame them. TRAX was the start of my love affair with Salt Lake City transit. The fundamental difference between TRAX and a bus is reliability--TRAX can keep a schedule. When I was commuting to the University of Utah from Sandy, I knew, to the minute, when TRAX left Sandy station and arrived at the University of Utah.

Much as I support buses, I cannot muster any love for them. Because I cannot trust a bus. By its very nature, a bus is an unreliable beast. No bus can keep a schedule, and the sheer uncertainty of that is maddening. Even when I rode a bus daily to work, I still found myself doing the 'bus bob', craning my neck down the street to look and see if the bus was coming yet. When the bus actually came varied by weather conditions, by time of day, and by individual driver. It was actually pleasing when a regular driver was consistently ten minutes late every day.  I knew exactly when I had to be at the stop and I no longer had to stand in the cold for ten minutes every morning, waiting for a bus that the schedule claimed had already arrived. 

The bus schedule was worse than useless. It only shows what time the bus is supposed to come, not when it actually will. It is possible and even likely to arrive ten minutes before the schedule time, and wait 20 minutes to catch a bus. But with 15 minute headways between buses or trains, there is only one chance to catch the right bus, so everyone is forced to be early, just to be sure. Thus, irregular arrival times vastly increasing their door to door travel time, to the enormous detriment of ridership.