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I was reading two and a half chapters of a book waiting for a bus in the suburbs when it occurred to me: what is delay, really?

Simply, delay is the extra time I didn’t plan on consuming in a journey.  Delay is what causes us to be late for appointments.  Delay is also how slow our trip is compared to other modes we could be using.  This is a subjective measure, and it is not what the government measures.  The government does not even measure delay for walking and biking, and it measures delay incorrectly for traffic and transit.

The only meticulously recorded measure of delay is really a measure of congestion.  Congestion is the wonderful condition that occurs when traffic approaches lane capacity.  It is measured by how much faster that traffic could be moving if only there weren’t so much traffic.  Every vehicle slows down to avoid collisions, and no one gets where they are going quickly.

If commuters understand their trip is going to involve congestion, and leave at an appropriate time to avoid or sit in it, then they are not really experiencing delay.  They are experiencing their planned trip duration.  Of course, if you are traveling through, or are a tourist, the congestion will most definitely be a delay for  you.  Your experience of delay is subjective, and therefore not eaily measured.

Transit agencies don’t consistently measure or record delay or congestion in the same way, but they do measure on-time performance.  Alas, they don’t report those data in a nationally consistent way, so I can’t play with it.  Unfortunately, on-time performance is not delay, either.  On-time performance is how tightly transit drivers and vehicles adhere to their schedule.  This gets beaten around on bus routes depending on how many passengers board and alight, and how much traffic the buses are enmeshed in.  On transit services with better control of their rights of way and schedules, it is easier to adhere to schedules, but things can still drift in response to overcrowding on platforms or breakdowns along the line.

On-time performance is not necessarily a problem for passengers, either,  If another bus or train is coming soon, then it is not a problem for riders.  If another vehicle isn’t coming for an hour, then you have a significant delay.  Hope you brought a book to read.

The worst failures in on-time performance are when transit vehicles bunch up, or “platoon”, with the lead vehicle carrying all the passengers and one or more vehicles following close behind with almost no passengers.  Not only is this inefficient, but it also means that passengers waiting at stops that missed the platoon are going to have to wait two or three times longer for another ride.  It might turn 15-minute headways into 1-hour headways, if three buses get platooned.

The real measure of delay on transit  should be about trip time, not schedule adherence.  Aside from vehicle speed, which is a function of number of stops and link speed, the most important determinant of trip time for passengers is headway.  If a rider can get on the next bus in 10 minutes to reach the same destination, their trip time is much less than if they have to wait an hour or more after a missed bus.  The on-time performance can be excellent for a bus route with a one hour headway, but the trip time for riders arriving at the stop ten minutes after the bus left their stop would be excruciatingly long.

As with traffic congestion, long headways separate the commuters from the tourists.  When I took commuter rail to school in Philadelphia, I had memorized the timetable for the Norristown line, because the trains only came every hour.  When I lived in Southwest Atlanta and commuted to work on the Red Line, I never worried about schedule.  I knew the train would be along in 10 minutes or so.

The reason I had to read most of a book that fine suburban day waiting for a bus was that I was not a regular bus rider.  I just walked to the bus stop like a novice and sat on the grass like a vagrant for most of an hour.  Before the bus actually came, two experienced riders materialized and waited, even though the bus was no where in site.  Regulars work their schedules around transportation when it is rare or time consuming, and experience no delay most days.

What about walking and biking?  Here the delay is more about opportunity cost alternatives.  If you have a car and there is parking where you are going, why would you walk?  My first journey most mornings is to a coffeeshop to write for an  hour or so before work.  I find it the best time to write.  This coffeeshop is within 20 minutes biking distance, but 10 minutes driving distance.  I have only biked to them a handful of times.  My bleary self does not want to deal with the pants cuffs, the toeclips and the legs, and I could get there in half the time in dry and speedy comfort.  So I take traffic, even though I should be strong, virtuous, heroic, and sustainable enough to bike in nearly the same time as drive, but two miles, four stoplights, six lanes of traffic and not much sidewalk separates the bikers from the cars pretty effectively.

Here again, there is a matter of experience.  Strong bikers and patient walkers will worry less about the distance, hills and traffic than the fair-weather outdoorsfolk. The real determinant of biking/walking versus traffic is proximity and parking.  My coffeeshop has ample parking out front, because they know how most people  get there.  I have never seen this parking lot full, so I just turn right on in for my early morning coffee and eggy sandwich.

If I lived in a denser neighborhood, where the coffeeshop was 2-3 blocks from my front door, not 2-3 miles, I would be much less likely to unpark my car, drive it there, and repark it near the coffeeshop.  I’d be just as likely to park 2-3 blocks away from the coffeeshop in most unmetered neighborhoods, so what was the point of ceding my parking spot in the first place?

Parking is more than a matter of convenience or inconvenience.  It actually spaces things out.  The average space per car in a parking lot is 325 square feet, half for the stall, and half for circulation.  That is probably bigger than your bedroom, and almost certainly bigger than your office space.  The biggest consumer  of space in traffic dependent places is stopping distance.  At the average speed of 31 MPH, each car needs a cushion of nearly 100 feet (2 stripes & a bit) between it and the next car.  The space needs of a passenger in average traffic are 1% of an acre.  This spreads everything out for walkers and bikers, making walking and biking even less appealing.  Adding more delay to every walk and bike trip.

Delay is subjective and complex, but that doesn’t mean we cannot do a better job of measuring it for transportation, not just traffic.