Analysis of Route 512 St. Clair — Part 2: Headways and Link Times

In the previous article, I reviewed the operation of the St. Clair route on Easter Sunday, 2007, as a starting point for a review of the route’s overall behaviour.  In this post, I will turn to data for the entire month that shows overall patterns and the amount of variation we might expect to find.

If the headways (the time between successive cars) range over a wide band, then service is perceived as irregular by riders regardless of what the printed timetable may say, and regardless of the “average” loads riding counts might report over an hourly period.  When headways are a mix of long and short values, the cars on long headways will carry heavier loads and the “average” experience for a rider is that they wait a long time for an overcrowded car.  The half-empty one a few minutes behind is little benefit to anyone, but it brings down the “average” load in the statistics.

Link times (the length of a journey from one point to another) reveal how predictable (or not) the time needed for a car to travel along a route will be.  If link times are consistent, this indicates that external effects (including unusual loads that stretch stop service times) are rare.  Even if the times vary over the course of a day, but do so within a predictable, narrow band, a route should be fairly easy to manage.  If the times vary a lot with no obvious pattern or are scattered within a wide band, then running times and service are hard to manage.

In reviewing St. Clair, I found that the operating environment, as it existed in April 2007, was quite benign compared to routes like King and Queen, the subject of previous analyses here.  This has important implications for the right-of-way project now underway on this route.  Congestion and random delays do play some role, but not an overwhelming one, in service quality.  Reducing the impact of congestion when and where it occurs will be beneficial, but more is needed than just getting autos out of the streetcars’ way to ensure reliable service. Continue reading