The other day I did a fun post with some back-of-the-envelope math to estimate what it might look like if every Portland bike commuter switched to a car for one day. Here’s a tidbit I didn’t have room to include: massive temporary shifts from bike to other modes already happen regularly.
They happen every time it rains. Rain eliminates about one in three bike trips citywide, to be precise.
Two weeks ago, we had a rare rainy spell on Tuesday and Wednesday. The Hawthorne Bridge bike counter showed a drop of 37 percent from the July average for those days.
Not all of those trips switched to cars, of course — it’s likely that a lot of them switched to public transit or (especially with non-work errands) were just skipped or delayed until the rain stopped.
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This isn’t just something that happens in the summer. Last November, city traffic count expert Tom Jensen sent BikePortland a chart that used “some more or less random samples” of bike counts to find a similar drop in bike traffic population that week:
So there’s both a seasonal variation in local bike traffic, and day-by-day variation.
Aside from the trivia about how many bike trips go away in the rain, we’ve got two quick takeaways from this:
No, this is not because Portlanders are wimps, etc. It’s because people find it more pleasant to bike when it is not raining than when it is raining. Generally mild weather is a big reason why a lot of people bike in Portland, San Francisco and Seattle (not to mention Amsterdam, Rotterdam and Copenhagen) in the first place.
Portland’s transportation system absorbs all these trips without much trouble. There’s definitely a slowdown in traffic when it rains, but some of that is due to the weather itself. On the other hand, rush hours are also noticeably more crowded on TriMet in heavy rain. Go figure.