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Slow Drive

About & methodology

What this is, how the numbers are made, and where they fall short.

Why this exists

I kept driving through the same long-term construction zones year after year and couldn’t stop thinking about it. Not my few minutes, but everyone’s minutes, added up. One corridor, times tens of thousands of cars a day, times several years. That’s a lot of collective time we all feel but rarely see added up.

Slow Drive is my attempt to put a rough number on that shared cost. It was never meant to be an official figure. It’s a back-of-the-envelope estimate of the scale of something we all sit through.

What it is and isn’t

It is

  • An independent look at the scale of collective time and traffic affected by major, long-running Edmonton road construction.
  • Built entirely from public City of Edmonton open data.
  • Upfront about every assumption.

It isn’t

  • An official City of Edmonton figure, or affiliated with the City.
  • A precise measurement. The numbers show rough scale, not exact counts.
  • A claim that any project is mismanaged. Delays are a normal part of building things; this just adds them up.

How the numbers are made

For each corridor, the estimate is simple:

daily traffic (real) × days under construction (real) × assumed delay per vehicle = cumulative hours

What’s real, straight from open data: which corridors are under construction, the permit start and finish dates, and the City’s own average traffic counts (AADT) for each road.

What’s assumed: the delay each passing vehicle loses to a work zone. It’s a small figure, roughly 0.2 to 2.0 minutes, set by the permit’s peak-hour restrictions. This is the one number that isn’t measured, and it’s the biggest lever in the model. Every project page shows the exact figure used and how it’s built.

Data sources (all public):

Where it’s rough (read this before you quote a number)

  • The delay-per-vehicle is an assumption. It’s an educated guess, not a measurement. If the real figure is half of what I used, the delay totals halve too, since they scale directly with it.
  • “Vehicles affected” counts trips, not people. A daily commuter passing a work zone is counted every day, for years. It’s total trip-exposures over the whole construction window, not unique drivers.
  • The totals are cumulative over multi-year windows. That’s why they look huge: years of small daily delays added up. Worth keeping in mind before reacting to the headline number.
  • Traffic volumes are recent averages, not live counts, and construction rarely disrupts a corridor evenly for its whole window.
  • The source only lists currently-open permits. The City drops permits once they close, so this is a snapshot of active work. Completed-project history is being built up over time.
  • Big projects span several corridors (for example the Yellowhead Trail Freeway Conversion). Those are grouped and counted once in the headline totals, but a single corridor’s duration can still be approximate.

Found something wrong? Good.

The goal is to get the scale roughly right and be completely open about how. If you know the assumptions can be better, a more realistic delay figure, a corridor that’s mislabelled, a project that’s actually finished, I want to hear it. Good corrections make this better and I’ll update it.

Independent, unofficial project. Not affiliated with, sponsored by, or endorsed by the City of Edmonton. Contains information licensed under the Open Government Licence, City of Edmonton. Data © City of Edmonton. Figures labelled “estimated” are derived by this project.

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