Speed limit contradictions with the Seattle Parks trail pilot

People have been using "ebikes" on Seattle's multi-use trails for some time.  These are primarily pedal assist ones capped at 15, 20 or 25 mph. Our household recently got an electric cargo bike with this feature. It's great because it's insurance that you can get where you need to go, even if a little tired or the hills are bigger than you realized on the route you picked (a critical need in a city where we have not yet put protected bike lanes on major flat and direct arterial routes).

Technically, ebikes on trails only became legal at the state level recently and so the parks department is doing a pilot (for which they want your feedback). The pilot includes a maximum 15 mph speed limit for all users, on ebikes or not. This is likely due to concern that people will blast past people on foot or slower or less confident trail users. Unfortunately that's been happening for some time and in my experience has little to do with whether the person is on an electric bike or not.

But this pilot points out a big contradiction in how we treat speed limits: for a trail, we can just lower all speed limits for all. For a road, we won't, at least not without studying each road and spending money.

I'm honestly pretty mad at this contradiction. The ostensible reason for a speed limit on trails is not a bad one: when you have different users (e.g. people on foot and people on bikes) who have different masses and speeds, it makes sense to slow down the faster ones to reduce risk of harm. That exact reason exists for all of our streets. In the vast majority of Seattle, your only choice to get where you need to if you're on a bike is mixing in traffic with 2000 plus pound vehicles that can go ten times as fast as you. In most of Seattle, if you're on foot, you regularly have to cross roads with those vehicles – and often walk in the street with them! (I could link to dozens of examples of people on foot being forced to mix with traffic unsafely if I spent five more minutes on this post but I won't).

However, to lower speed limits on most of our roads, despite a city council ordinance lowering default speed limits, SDOT is insisting that we study roads neighborhood by neighborhood. They will want to prove that it won't cause congestion to lower them. They will want to demonstrate that the road design will result in 85th percentile speed being near the new speed limit. If we can't prove those things, they will insist we make changes to the road (or possibly none if too much traffic). Never mind there are massive inequities in road speeds across Seattle. Never mind that slower speeds are the most important tool we have for reducing road injuries and death. We "can't" lower speed limits "if people won't follow them". That's somehow unfair.

But we are doing just that on multi-use trails right now though. Few are going to go less than 15mph on a bike on the Mountains to Sound trail near my house. Nothing about the trail design would make you feel that 15 mph is an obvious reasonable maximum speed. I always slow way down around other users of course, but not everyone does and many haven't been for years, long before this pilot.

Why is it okay to lower speed limits on some of our street infrastructure but not others? Why can't we lower speed limits on all our streets? Now?